Benign bone tumors - Dr. Sachin M

Classification of
bone tumors &
Benign bone
tumors
PRESENTED BY: DR. SACHIN. M.
2ND YEAR PG, DEPT OF ORTHOPAEDICS, SMCH
MODERATOR: DR. ARIJIT DHAR
ASSOCIATE PROFESSOR, DEPT OF ORTHOPAEDICS, SMCH

CLASSIFICATION OF BONE
TUMORSSite of origin Benign Malignant
Osteogenic Osteoma
Osteoid osteoma
Osteoblastoma
Osteosarcoma
Cartilage Osteochondroma
Chondroma
Chondroblastoma
Chondromyxoid fibroma
Chondrosarcoma
Fibrogenic Fibroma
Desmoplastic fibroma
Fibrosarcoma
Fibrohistiocytic Benign fibrous histiocytoma Malignant fibrous histiocytoma
Primitive neuroectodermal
tumor
Ewing’s carcoma
Haematopoietic Plasma cell myeloma
Lymphoma NOS
Giant cell tumor GCT Malignancy in GCT

CLASSIFICATION OF BONE
TUMORSSite of origin Benign Malignant
Notochordal Chordoma -
Vascular Haemangioma Angiosarcoma
Smooth muscle Leiomyoma Leiomyosarcoma
Lipogenic Lipoma Liposarcoma
Neural Neurilemmoma -
Miscellaneous - Adamantinoma
Metastatic malignancy
Miscellaneous lesions: SBC, ABC; Fibrous dysplasia; Osteofibrous dysplasia; Langerhans cell
histiocytosis; Erdheim-Chester disease; Chest wall hamartoma
Joint lesions: Synovial chondromatosis

OSTEOCHONDROMA
 Also known as EXOSTOSIS
 Two forms: Solitary and Multiple (Diaphyseal aclasis or HME, 15% cases)
 WHO definition: A cartilage capped bony projection arising on the external surface of the
bone containing a marrow cavity which is continuous with that of the underlying bone.
 THE MOST COMMON: 10-15% of primary bone tumors, 20-50% of benign bone tumors,
bone tumor in children
 ETIOLOGY:
o Mutation in gene encoding exostin 1 (EXT - 1)
o Other causes include prior surgery, physeal injuries, post-radiation
o Age: first 3 decades of life
o Sex: M:F = 2:1
o Site: metaphysis of long bones – distal femur > proximal tibia > proximal humerus
flat bones – ilium and scapula

OSTEOCHONDROMA
 CLINICAL FEATURES:
o Asymptomatic, incidentally found
o Hard, immobile, non-tender swelling of long duration
o Painful swelling: in cases of bursitis, fracture, pressure symptoms, ischemic necrosis,
malignant changes
o Others: growth disturbance, limitation of movements, deformity, fracture
 RADIOGRAPHY:
o X-ray: sessile / pedunculated, eccentric bony outgrowth from the metaphysis, composed
of cortex and medullary cavity which are in continuity with that of the underlying bone
o Directed away from the growing end of the bone
o Cartilage cap – not seen in the plain radiograph
o MRI: characterization of the lesion and identifies associated complications
o CT scan and USG

OSTEOCHONDROMA
 PATHOLOGY:
o Gross appearance: firm, lobulated, sessile / pedunculated mass covered with fibrous tissue
or perichondrium which is in continuity with the periosteum
o Cartilage cap lies beneath the fibrous capsule; its size decreases with age
o Microscopy: 3 layers are seen – periosteal layer, cartilage layer and bony layer (outside in)
o Cartilage layer - superficial chondrocytes in clusters and deep chondrocytes in vertical
bands
o Bony layer - trabecular bone with marrow spaces
o Features s/o malignant transformation: loss of cartilage architecture, myxoid change, high
mitotic activity, increased chondrocytes and atypia, necrosis, wide fibrous bands

OSTEOCHONDROMA
 TREATMENT:
o Conservative for asymptomatic cases
o Indications for surgical excision – cosmetic, decreased joint function, painful bursitis,
fracture of the lesion, impingement syndrome, malignant changes
o Complete excision along with the perichondrium
 Malignant transformation:
o 1% in solitary and 20% in multiple osteochondromas
o Loss of sharp definition of the mass, lytic areas in the osseous structures or calcification of
the cartilage cap.

HEREDITARY MULTIPLE
EXOSTOSES Also known as multiple osteochondroma, diaphyseal aclasis
 Autosomal dominant with incomplete penetrance – males are affected, females are
carriers
 Lesions arise from osteochondral ossification
 3 tumor suppressor genes : EXT 1, EXT 2 and EXT 3 gene
o EXT 1 gene: severe form, >20 sites, males, deformities and functional limitation +
o EXT 2 gene: mild form, <5 sites, females, without deformities and limitation
 Positive family history in 2/3rd of the cases
 Presents earlier than solitary type – first 2 decades of life
 Deformities, decreased joint movements – affects daily activities
 Short stature – limbs shorter than the trunk
 Other deformities – ulnar shortening with forearm bowing, tibiofibular synostosis, valgus
deformity of ankle, genu valgum, coxa valga, scoliosis

HEREDITARY MULTIPLE
EXOSTOSES Sessile >>> pedunculated – more severe deformities
 Radiological and pathological findings – same as solitary type
 Treatment: Excision of symptomatic exostosis and correction of deformity and LLD
 Malignant transformation: lesions in pelvis, scapula, proximal femur and in patients with
family history

OSTEOCHONDROMA VARIANTS
 SUBUNGUAL EXOSTOSIS / DUPUYTREN’S EXOSTOSIS
o Dorsal / dorsomedial aspect of distal phalanx
o Painful lesions with skin ulceration
o Toes (90%) – great toe is the most affected
o No continuity with the underlying bone, cartilage cap – fibrocartilage
o Complete excision of the lesion + / - nail
 DYSPLASIA EPIPHYSEALIS HEMIMELICA
o Osteochondromas from epiphysis from one side of single extremity
o Medial > lateral side of epiphysis
o Localized, classic and generalized form
o Boys > girls
o Complete or partial excision + corrective osteotomies

OSTEOCHONDROMA VARIANTS
 TURRET EXOSTOSIS
o Dorsum of middle and proximal phalanx
o Ossification of matured subperiosteal hematoma
o Excision after complete maturation
 BIZARRE PAROSTEAL OSTEOCHONDROMATOUS PROLIFERATION OR
NORAH’S LESION
o Reactive process to trauma
o Metacarpals and metatarsals are affected more

ENCHONDROMA
 ETIOPATHOGENESIS:
o Benign hyaline cartilage tumor occurring in the medulla of bones in young adults,
destroying the cancellous bone
o Jaffe’s hypothesis: embryonic rests / nidi derived from the epiphyseal plate
o Constitutes: 12 – 24% of benign bone tumors, 3 – 10% of all bone tumors
o Age: 5 to 80 years; 3rd to 4th decade of life
o Sex: males and females are equally affected
o Site: 50% of the cases in HAND (most common primary tumor of hand) – little finger; proximal
phalanx > metacarpal > middle phalanx
o 25% cases in long bones – femur > humerus > tibia
o 7% cases in small bones of foot

ENCHONDROMA
o Asymptomatic, incidentally found
o Painless, slowly growing swelling or painful limitation of joint movements
o Exophytic growth: Enchondroma protuberans
 RADIOGRAPHIC FEATURES:
o X-ray: small, well demarcated, lobulated, translucent lesion
o Cortical thinning, bony expansion, intralesional stippled calcification (rings and arcs like densities)
o Cortical breaks with soft tissue mass in small bones
o MRI: lobular pattern; T2W high signal intensity – hyaline cartilage; Gd contrast – fibrovascular
septae.

ENCHONDROMA
 PATHOLOGY:
o Gross: lobulated, bluish-white, translucent lesion
o Microscopy: hyaline cartilage – avascular, hypocellular with
chondrocytes in lacunae, single nucleus and eosinophilic
cytoplasm
 TREATMENT:
o Intralesional curettage with complete excision of extra-
osseous component
 RECURRENCE: rare and more likely in long bone
enchondromas
 MALIGNANT TRANSFORMATION:
o Small bones < 1%; Other solitary lesions 2% - 5%; multiple
lesions 10% - 50%.
o Wide excision and reconstruction

MULTIPLE ENCHONDROMATOSIS
 OLLIER’S DISEASE
o Rare, non-hereditary, characterized with multiple enchondromas, predominant unilateral
distribution
o Described as dyschondroplasia of any portion of the enchondrally ossified bones
o PTHLH receptor mutations – PTHR 1
o Commonly seen in 1st and 2nd decades of life, affecting hand bones.
o Ranges from single bone to wide spread bilateral involvement
o Histopathological: more cellular than enchondroma with nuclear atypia

MULTIPLE ENCHONDROMATOSIS
 MAFFUCI’S SYNDROME
o Multiple enchondromatosis along with soft tissue and rarely visceral hemangiomas
o Occurs as a result of neural abnormalities – abnormal focal proliferation of nerve endings
influences the proliferation of cartilage and vessels
o Deformities of hand and long bones
o X-rays: bony lesions with deformities; soft tissue hemangiomas with phleboliths
o 50% of cases will show malignant transformation
 METACHONDROMATOSIS
o Rare, hereditary, autosomal dominant
o Multiple enchondromas + multiple osteochondromas
o Affects long tubular bones

PERIOSTEAL CHONDROMA
o Also known as juxtacortical or parosteal chondroma
o Occurs within and beneath the periosteum and extracortical, at the sites of tendon and
ligament attachment
o Rare: constitutes <2% of chondromas
o Age: 3rd and 4th decades of life; Sex: both are equally affected
o Site: Metaphyseal or metadiaphyseal region of long bones, small tubular bones, proximal
humerus.
o Small, slowly growing, painful swelling
o Painful limitation of joint movements

PERIOSTEAL CHONDROMA
o X-ray: faintly outlined, lightly calcified, small, ovoid soft tissue mass
which is extracortical
o Cortical scalloping +/- sclerosis, thin periosteal shell, chondroid
matrix mineralization
o MRI: lobular, intermediate T1W and high T2W signal; thin
peripheral and septal contrast enhancement
 PATHOLOGY: same as enchondroma with mild nuclear atypia
 TREATMENT:
o Excision of tumor and capsule
o En bloc resection with reconstruction
o Hemicortical resection

CHONDROBLASTOMA
 WHO Definition: highly cellular and relatively undifferentiated tumor, made up of rounded or
polygonal chondroblast like cells with distinct outlines and multinucleated giant cells of
osteoclast type arranged singly or in groups with typical cartilaginous matrix with areas of focal
calcification.
 ETIOPATHOGENSIS:
o Constitutes 1% of all bone tumors, affecting epiphysis or apophysis
o Arise from secondary ossification centres
o Age: in 2nd decade of life; before closure of physis
o Sex: M > F – 2:1
o Site: Long bones – proximal and distal femur, proximal tibia and proximal humerus
o Foot bones – talus and calcaneus
o pain – dull aching / boring; mild to severe
o Swelling around the joint; joint effusion, antalgic gait, painful terminal joint movement

CHONDROBLASTOMA
 RADIOGRAPHY:
o X-ray: well-defined, lytic areas in epiphysis with thin, lobulated, sclerotic margin
o Matrix mineralization seen in 30% cases
o Thick periosteal reaction with reactive bone formation seen in metaphyseal lesions
o Bone expansion in foot bones
o MRI: intermediate T1W and low T2W signal intensity; multiple fluid-fluid levels due to
secondary ABC
 PATHOLOGY:
o Gross: dark red/tan colored, hemorrhagic, friable with scattered small yellow zones of
calcification
o Microscopy: compact round/polygonal cells with clear to slightly eosinophilic cytoplasm
and nuclei with longitudinal grooves, scattered giant cells.
o Pericellular type of calcification – chicken wire appearance

CHONDROBLASTOMA
 TREATMENT:
o Intralesional curettage with reconstruction
o En bloc resection and reconstruction for recurrent tumors
 RECURRENCE:
o 15% to 20% of cases, occurs within first 2years of curettage
o Pulmonary metastasis in cases of recurrent tumors
o Post-radiation sarcomas

CHONDROMYXOID FIBROMA
o Constitutes 1% of all bone tumors
o WHO definition: lobules of spindle or stellate shaped cells with abundant myxoid or
chondroid intercellular material
o Tumor mainly consists of hydrated proteoglycans and only minor amounts of collagen –
myxoid matrix appearance
o Age: 50% of cases - in 2nd to 3rd decade of life
o Sex: Males are affected more
o Site: metaphysis of long bones (65%) > foot bones (20%) > flat bones
o Long bones – Tibia > Femur > Fibula
o Foot bones: phalanges > metatarsals
o In 95% cases, lesions are located in medullary cavity

o Pain +/- : dull aching / boring, increases on exertion
o Slow growing swelling with associated soft tissue component
o Shiny stretched skin over the lesion
o X-ray: eccentrically placed, geographical lesions with a narrow zone of transition, sclerosis
and inner scalloping – bite like destruction
o Thinned out or broken outer cortex due to expansion with soft tissue shadow
o Internal trabeculations without matrix
o Fusiform expansion of narrow or small tubular bones due to involvement of entire bone width
o MRI: low T1W and heterogeneous T2W signal

 PATHOLOGY:
o Gross: eccentric / fusiform, solid tumor mass of greyish white or bluish grey color, firm
consistency
 TREATMENT: Intralesional curettage or En bloc resection and reconstruction
 RECURRENCE: 3% to 22%
 MALIGNANT TRANSFORMATION: in 1% - 2% of cases

OSTEOMA
o Most of them occurs spontaneously
o Trauma, inflammation / infection, developmental factors
o Gardner syndrome: Autosomal dominant disorder – multiple osteoma + intestinal
polyposis + multiple cutaneous and subcutaneous lesions
o Age: seen in mature skeleton; 4th to 5th decades of life
o Sex: M > F, 2:1
o Site: most commonly affects membranous bones of skull and face – 75% cases lesions
arise from frontal and ethmoid sinuses
o Uncommon sites include clavicle, appendicular skeleton, rarely pelvis
 CLASSIFICATION:
o Sinonasal osteomas (skull)
o Parosteal osteomas (long bones)

OSTEOMA
 CLINICAL FEATURES: depends on the size and location of the lesions
o Small lesions – asymptomatic
o Large paranasal lesions:
• Nasal: Sinusitis, nasal discharge, headache, pain, loss of sense of smell
• Ocular: exophthalmos, double vision, loss of vision
• Intracranial: erosion of cranial wall, perforation of dura, frontal lobe compression and frontal
lobe symptoms
o Parosteal osteomas: pain and swelling
o Round-to-lobular, 3-4cm homogenous radiodense mass with smooth surface with no
cortical invasion
o In sinonasal region: forms polypoid Intracavitary growths with central areas of
radiolucency

OSTEOMA
 PATHOLOGY:
o Histology is same as normal bone
o Slow growing tumor – dense compact bone
o Rapid growing tumor – vascular fibrous stroma with newly formed osteoid or osseous
spicules are seen
 TREATMENT:
o Conservative if asymptomatic
o Surgical excision – if symptomatic, for cosmetic reasons or for rapidly growing ossifying
fibroma in spine

OSTEOID OSTEOMA
o Constitutes 10% of benign bone tumors
o Various etiological factors – trauma, inflammation and developmental causes secondary
altered vascularity in the affected area
o These are small bone forming lesions which are < 2cm in size and exhibits a central well-
defined hypervascular area of rarefaction – NIDUS
o NIDUS – composed of vascular fibrous tissue, proliferating fibroblasts and minute spicules
of newly formed osteoid, and is surrounded by a zone of normal appearing sclerotic bone
o Age: 5 -30 years of age, 90% of cases
o Sex: M > F; 2:1 to 3:1
o Site: Long bones – proximal femur > proximal tibia
o Other sites include – spine(posterior elements), humerus, hand & foot bones
o Intra-articular lesions – hip is most commonly affected

OSTEOID OSTEOMA
o Pain – progressive, continuous, night pains, referred to joints
• Responds to NSAIDS (pain and sclerosis are attributed to PGE2 and PGI x COX inhibitors)
o Localized, tender swelling – fusiform in shape
o Limp – in cases of lower limb lesions
o Painful limitation of joint movements – in intra-articular lesions
o Deformities in long standing cases
o Spine – localized back pain, muscle spasm, secondary scoliosis and pelvic tilt

OSTEOID OSTEOMA
 RADIOLOGICAL FEATURES:
o X-ray: solitary, small rarefied lesion, surrounded by sclerotic and thickened bone with
varying amounts of calcification in the nidus
o Bone scintigraphy
o Radionuclide scan: increased uptake by nidus; DOUBLE DENSITY SIGN is very specific and
diagnostic
o CT scan: low attenuation, round to oval nidus with varying degrees of central
mineralization and surrounding sclerosis
 PATHOLOGY:
o Central area of osteoid production surrounded by sclerotic bone
o Numerous osteoblasts surrounds the osteoid within vascularized connective tissue

OSTEOID OSTEOMA
 TREATMENT:
o Conservative: self limiting disease – requires NSAIDs for several months to years;
associated with long term sequelae like deformities
o Surgical:
o Indications include failure of conservative treatment, patients not willing to tolerate pain
and long term medical treatment and patients with NSAIDs intolerance
o Surgeries include Open excision by en bloc resection or cortical shaving and curettage of
nidus; MIS – percutaneous CT guided excision or RFA
o Other modalities or treatment: image guided cryotherapy, drill-trepanation +/- ethanol
injection, LASER photocoagulation, arthroscopic excision of intra-articular lesions
 RECURRENCE: most common complication which occurs due to incomplete excision of
nidus

OSTEOBLASTOMA
o Constitutes 3% of all benign bone tumors
o Vascular, bone forming tumor which is histologically similar to nidus of osteoid osteoma
but lacks reactive sclerosis
o Bigger in size >2cm
o Age: 10-25 years
o Sex: M > F; 2:1
o Site: Spine (posterior elements) – affected in 1/3rd of the cases; metaphysis / diaphysis of
long bones (femur, tibia); hand and foot bones
o Rarely multifocal – either in a single bone or in multiple bones
o Pain: dull aching/boring; neither nocturnal nor relieved by NSAIDs
o Spine: stiffness, painful scoliosis with or without neurological deficits.

OSTEOBLASTOMA
 RADIOGRAPHIC FEATURES: Depends on the size, location and degree of ossification
o X-ray: radiolucent / mottled, well-circumscribed lesions with variable amount of central
ossification and thin peripheral shell reactive bone
o Tumor attenuates the cortex as it enlarges, but delimited by a shell of periosteal new bone
o Spine – enlarged posterior elements along with an extraosseous mass
o Bone Scintigraphy: intense tracer uptake
o CT scan: investigation of choice
o MRI: for evaluation of soft tissue and spinal involvement

OSTEOBLASTOMA
 PATHOLOGY:
o Gross: deep red, friable and gritty
o Microscopy: haphazardly arranged woven /
trabecular bone lined by plump osteoblasts in a
very vascular stroma with varying degree of
mineralization of bone
o Mitotic figures and rarely, osteoclast like giant cells
will be seen
 TREATMENT:
o Surgery: complete removal by Curettage or en
bloc resection; Decompressive laminectomy to
relieve pressure on spinal roots
o For inaccessible tumors – moderate dose of
cobalt therapy

GIANT CELL TUMOR
o Commonest benign tumor encountered by an Orthopaedician
o Benign but locally aggressive tumor
o In Caucasian – 5% of all skeletal tumors; 20% of all benign tumors
o In Orient – 20% of all skeletal neoplasms
o Age: skeletally mature individuals with peak incidence in 3rd decade of life
o <2% cases in patients with open physis, 10% cases in patients aged > 65years
o Sex: M<F; 1:1.5
o Site: epiphyseo-metaphyseal region of long bones – Distal femur > proximal tibia > distal
radius
o Uncommon sites include sacrum, pelvis, distal tibia, proximal humerus, proximal
femur/fibula and very rarely hand and foot bones in younger age group, spine.

GIANT CELL TUMOR
o Pain – variable severity + / - mass or swelling
o Trauma / pathological # draws attention to the tumor (5 to 10%)
o X-ray: lytic lesion with well defined margins in the epiphysis extending to metaphysis and
close to subchondral bone with thin subperiosteal new bone formation
o No mineralized tumor matrix is seen and tumor bulges beyond the cortex
o Multiple traversing septae – SOAP BUBBLE APPEARANCE
o Multiple fluid – fluid levels due to secondary ABC
o MRI: low T1W and high T2W signal intensity with multiple fluid – fluid levels (secondary ABC)

GIANT CELL TUMOR
 RADIOGRAPHIC CLASSIFICATION: By Campanacci
o Grade I: well-marginated border, thin rim of mature bone, intact / slightly thinned out
cortex
o Grade II: relatively well-defined margins but no radio-opaque rim, cortex is thinned out
and moderately expanded
o Grade II with fracture
o Grade III: fuzzy borders – permeative growth
o Tumor bulged into the soft tissue – soft tissue mass is not limited by an apparent shell of
reactive bone and do not follow the contour of the bone.

GIANT CELL TUMOR
 PATHOLOGY:
o Gross: eccentrically placed epiphyseal lesion with bony expansion, surrounded by thin
reactive bone +/- soft tissue expansion; reddish brown to yellow in color
o Microscopy: round to polygonal mononuclear cells
o Giant cells – multinucleate, osteoclast like with > 50 nuclei, uniformly scattered throughout the
tumor; increased mitoses and intravascular invasion
o Histological variability is seen between & within the tumor

GIANT CELL TUMOR
 TREATMENT:
o Intralesional curettage + reconstruction
o Excision for expandable bones like distal ulna and upper fibula
o En bloc resection & reconstruction - multiple recurrence + extra-osseous component
- multicentric + articular degeneration
- bone salvage leading to decreased bone integrity
o Chemotherapy – no effective chemotherapy till date
o Radiotherapy – unresectable lesions in spine and sacrum
o Embolization – at monthly intervals in unresectable GCT for pain palliation
o Bisphosphonates – effective adjunctive in the management of large lesions
 RECURRENCE: 15% cases, within first 2years of resection
o Pulmonary metastasis in 1% – 6% of cases of GCT

FIBROUS DYSPLASIA
o Constitutes 5 to 7% of all benign bone tumors
o Sporadic, non-hereditary, developmental disorder of the skeleton characterized by solitary
solitary (monostotic) or multifocal (polyostotic) medullary fibro-osseous lesions containing
containing fibroblast like spindle cells and immature woven bone
IL – 6 production GNAS-1 mutation Hormonal alteration
Increased resorption
Of bone
Alters cellular differentiation
and osteoclast proliferation
- More hormonal receptors
on osteoblasts
- Exacerbation during
pregnancy
Inability to produce mature lamellar bone
Immature fibro-osseous tissue with immature woven bone

FIBROUS DYSPLASIA
o Monostotic >>> polyostotic – 8 to 10 : 1
o Age: first 3 decades of life, but polyostotic form present early with more severity
o Sex: both are equally affected
o Site: any part of the skeleton
o Monostotic form – ribs, proximal femur, craniofacial bones
o Polyostotic form – femur, tibia, pelvis and foot
 TYPES OF FIBROUS DYSPLASIA:
o Monostotic form
o Polyostotic form
• Monomelic form
• Polymelic form
o Polyostotic with endocrinopathy - McCune Albright syndrome, Mazabraud’s syndrome
o Osteofibrous dysplasia

FIBROUS DYSPLASIA
 McCUNE ALBRIGHT SYNDROME: Triad of
o Polyostotic fibrous dysplasia seen in 30-50% of cases
o Cutaneous café-au-lait spots, located on ipsilateral side with Coast of Maine border
o Endocrine dysfunction – Gonadotrophin independent precocious puberty, hyperthyroidism, high
growth hormone, FGF23 mediated renal phosphate wasting, Cushing’s syndrome
o Females are affected more than males
 MAZABRAUD’S SYNDROME:
o Polyostotic form with soft tissue myxomas which arise adjacent to the affected long bones
in the later period
 CHERUBISM:
o AD form of fibrous dysplasia with symmetric involvement of both the mandible and the
maxilla
o Commonly seen in 2nd decade of life

FIBROUS DYSPLASIA
o Monostotic form: asymptomatic
o Polyostotic form: severe and symptomatic
o Pain – due to structural weakness and microfracture
o Swelling
o Deformity – due to abnormal bone growth and remodeling after micro-fractures
- Varus deformity of proximal femur (Shepherd’s crook deformity) – most common
deformity associated with antalgic gait, LLD and high risk of pathological #
- Others: tibial bowing, rib & chest wall masses, bossing of the skull, prominent jaw

FIBROUS DYSPLASIA
o X-ray: well-defined, expansile, medullary lesion in the metaphysis / diaphysis +/-
endosteal scalloping and varying degree of translucency
o Ground glass appearance – due to immature fibro-osseous tissue
o Expansive remodeling leads to thick, sclerotic, reactive bone formation called RIND
o Rarely, islands of cartilage are seen – enchondral ossification
o Bone scintigraphy: extent, distribution of lesions; detection of stress fractures
o CT scan: extent of the lesion
o MRI: low T1W and high T2W signals; cystic changes seen in long standing cases and detects
malignant transformation

FIBROUS DYSPLASIA
 PATHOLOGY:
o Gross: expanded bone with gray color tissue with a
firm-to-gritty consistency; cystic areas with yellow-
tinged fluid will be seen
o Microscopy: well-circumscribed lesions
o Fibrous component – relatively avascular;
cytologically bland spindle cells with low mitotic rate
without atypia
o Osseous component – irregular curvilinear
trabecular or woven bone (Chinese characters or
letter like pattern)
o Secondary myxoid and ABC like changes may be
seen

FIBROUS DYSPLASIA
 TREATMENT: depends on age, type, site and extent of the lesions and symptoms
o Monostotic asymptomatic lesions – observation and follow-up
o Large symptomatic lesions – require active management
o Medical management: Bisphosphonates (2nd and 3rd generation) along with Vit D and
Calcium supplements
• Increases cortical thickness, ossification of the lesion, improved function and prevents
pathological #
o Surgical management: in progressive deformity, large painful lesions, non-union or failure
of medical therapy
• Curettage + Bone grafting
• Cortical strut allograft should be used; autograft & CBG gets resorbed earlier
• Internal fixation when indicated and Osteotomies for deformity correction
 Malignant transformation: 0.5% in monostotic form and 4% in McCune Albright
syndrome – osteosarcoma / fibrosarcoma; carries poor prognosis

NON-OSSIFYING FIBROMA (NOF) OR
FIBROUS CORTICAL DEFECT
o Non-neoplastic, developmental disorder characterized with fibrous proliferation in the
metaphysis of long bones
o AKA Fibrous cortical defect or Fibroxanthoma
o Trauma in the region of muscle attachment  focal sub-periosteal hemorrhage
o Age: occurs in first 2 decades (30% of cases)
o Sex: M>F 2:1
o Site: metaphyseal, eccentrically located – tibia and femur
o Usually asymptomatic and found incidentally
o Rarely – swelling, mild deformity and pathological #

o Well-defined, oval, lytic lesion located eccentrically in the metaphyseal cortex, surrounded
by thin sclerotic rim which is deficient on the external side of the lesion
o Long axis of the lesion is parallel to that of the long bone
o Large lesions will be multiloculated with the risk of pathological #
o After maturation – lesion gets filled with fibro-osseous tissue
 RITSCH STAGING OF FCD:
o Stage A: small, oval lesion, adjacent to growth plate
o Stage B: migrates toward metaphysis with bone growth, increases in size, polycyclic and
grape shaped borders
o Stage C: involution and maturation – mineralization occurs from diaphysis towards the
growth plate
o Stage D: completely calcified lesion

 PATHOLOGY:
o Spindle shaped fibroblasts in whorled and storiform
pattern within the cortex
o Scattered osteoclast type giant cells, foam cells,
lymphocytes and hemosiderin pigment seen
 TREATMENT:
o Asymptomatic lesion – conservative
o Large and lytic lesion – regular follow-up
o Curettage and reconstruction – for symptomatic,
large, non-ossified, lower limb lesions and lesions
which are at higher risk pathological #

OSTEOFIBROUS DYSPLASIA
o Self-limiting, rare, benign, fibro-osseous lesion – 0.2% of all primary bone tumors
o AKA Kempsen - Campanacci lesion or Cortical fibrous dysplasia
o Age: in first 2 decades of life
o Sex: both males and females are equally affected
o Site: Leg bones (mid-diaphysis and proximal metaphysis of Tibia > ipsilateral or
contralateral fibula)
o Lesion will be epicentered in the cortex
o Other sites are radius and ulna
 CLINICAL FEATURES: 1/3rd of the cases are found incidentally
o Swelling with bowing of the leg +/- pain
o Pathological #

o X-ray: well-defined, lytic, intra-cortical lesion
surrounded by a zone of sclerosis involving the
anterior cortex of tibia +/- tibial bowing
o May have multiple lucencies
o Aggressive lesions involves metadiaphyseal region
o CT scan: cortical lesion with expansion and
thinning of the cortex with medullary or soft tissue
extension

 PATHOLOGY:
o Gross: whitish / yellowish solid lesion;
expanded and thinned out cortex
o Medullary extension, if present, will be
demarcated by a sclerotic rim
o Microscopy: loose fibrous stroma with
spicules of woven bony trabeculae that are
lined by a layer of osteoblasts
o Central zone: more immature woven bone
trabeculae
o Peripheral zone: more mature lamellar
bone which blends with the normal
surrounding bone

 TREATMENT:
o Benign in nature – regular follow up
o Bowing of the bone – bracing to prevent # and to minimize deformity
o Surgical intervention for extensive / progressive lesions with deformity or for a
pathological #
o Curettage with bone grafting + internal fixation after deformity correction
o Extra-periosteal excision and appropriate reconstruction with bone grafts

UNICAMERAL BONE CYST
o AKA solitary / simple / juvenile bone cyst
o It is an intramedullary, unilocular, serous or serosanguinous fluid-filled bone cavity
o There are various etiological theories:
• Virchow – abnormalities in the local circulation
• Jaffe & Litchenstein – primary trauma leads to change in local circulation
• Mirra – intraosseous synovial cyst by electron microscopy
• Cohen – theory of veno-occlusion, in the intramedullary space
o Cavity is lined by synovial cells resembling type A and B cells of synovial tissue
o Fluid analysis reveals high oxygen free radicals, prostaglandins, IL-1, proteolytic enzymes

o Age: first 2 decades of life (85% of cases)
o Sex: M:F, 3:1
o Site: metaphysis of long bones; Proximal humerus > proximal femur > proximal tibia.
o Other sites are: ilium, distal humerus, distal femur and tibia, calcaneus, talus, radius, ulna,
ribs
o Asymptomatic and incidentally found in some cases
o Local pain due to #; local swelling and tenderness
o Intermittent limp in case of weight bearing bones
o If fractured – heals rapidly within few weeks and it leads spontaneous obliteration of the
cyst after the fracture union

o Cyst – remains in its juxta-epiphyseal location in most cases
o May Induce growth disturbances and deformity
o In proximal femur – coxa vara > coxa valga deformity
o In 30% cases, cyst displaces towards the diaphysis due to continuous bone growth and
remodeling of the metaphysis
o Active bone cyst – continuously enlarges when it is located adjacent to the growth plate
o Latent bone cyst – cyst becomes latent as it moved away from the growth plate

o X-ray: large, well-localized, radiolucent, expansile lesion with a narrow zone of transition
and no matrix
o Cortex is thinned out with medullary scalloping with smooth periosteal surface
o Loculated appearance due to ridges over the inner surface of the cyst, but fibro-osseous
septae develops after fracture healing
o Fallen leaf sign – fractured cyst wall fragment fallen into the fluid cavity
o MRI: single cavity with central fluid collection

 PATHOLOGY:
o Gross: fusiform expansion of bone
o Cortex – egg-shell thin, semitranslucent,
bluish in color and easily penetrable
o Cyst fluid – yellow / straw colored fluid;
hemorrhagic if there is recent trauma
o Microscopy: Cyst wall – layers of fibroblasts
lying on vascular collagenous or myxomatous
tissue containing multinucleated giant cells,
foam cells, containing hemosiderin and lipids,
and cholesterol crystals imbedded in fibrin
o Cortical wall – loosely trabeculated osseous
tissue and many thin-walled vessels

 TREATMENT: depends on the stage of the disease
o Latent stage – observation and follow up
o Active stage – need intervention
o Pathological # - stabilize and observe
o Percutaneous aspiration and steroid injection / autogenous bone marrow / commercially
available bone substitutes
o Surgery – curettage + bone grafts / substitutes
 RECURRENCE: 10% to 88%
o Depends on age (<10yrs), site (proximal humerus), proximity to physis, stage of the disease
(active cysts) and type of treatment

ANEURYSMAL BONE CYST
o AKA multilocular hematic cyst / giant cell reparative granuloma
o Benign but locally aggressive lesion
v/s
o Incidence of primary lesion – 0.14 – 0.32 / 1,00,000 individuals
o Primary ABC – 70% cases; Secondary ABC – 30% cases
Non-neoplastic Neoplastic
Local vascular disturbance TRE17 / USP6 translocation
^ Intra-osseous pressure ^ matrix metalloproteinase 9, 10
Hemorrhage and local destruction Degradation and remodeling of bone matrix

o Age: first 2 decades of life;
o Sex: M>F
o Site: metaphysis of long bones – femur, tibia and humerus; posterior elements of vertebral
bodies
o Pain: due to bony destruction and pathological #
o Swelling and limitation in joint movements
o In spine: backache, functional spinal deformity and rarely neurological deficits

o X-ray: centrally / eccentrically located, ballooned out, well-defined lytic lesion without
matrix and with a thin shell of reactive periosteal bone
o Cortical thinning and destruction. Internal septations may be seen.
o MRI: internal septations and fluid-fluid levels – due to difference in densities within the
lesion as a result of settling of blood cells

 PATHOLOGY:
o Gross: thin shell of bone, easily
penetrable; reddish brown, liver-like
friable mass with interspersed
particles of bone; fibro-osseous
septa throughout the tumor
o Microscopy: small and large pools of
blood within fibro-osseous septa
replaces spongy bone and marrow
o Connective tissue lining the vascular
spaces contains multinuclear
osteoclast like giant cells, new bone
formation and ‘blue bone’

 TREATMENT:
o Surgery: Curettage or en bloc resection
o Intralesional sclerotherapy using sclerosants
o Repeated selective arterial embolization in the lesions located in the areas that are difficult
to access
 RECURRENCE:
o 5% to 35% after curettage
o Risk factors for recurrence - Age <12yrs, open epiphysis, high mitotic index, predominant
cellular component with sparse osteoid component on histology.

Benign bone tumors - Dr. Sachin M

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