The document summarizes key aspects of the lymphatic system and disorders that can affect it. It describes the functions and divisions of the lymphatic system, including circulating lymph and lymphoid tissues. It then discusses several lymphatic disorders like lymphedema, lymphangiomatosis, and lymphangiosarcoma. The document also reviews the spleen's roles in filtering blood and immunity. It lists several disorders that can cause splenomegaly and types of splenic disorders. Finally, it examines the thymus's role in immunity and discusses thymic hyperplasia, thymoma, and characteristics of benign and malignant thymoma.

1. Aamir Rauf Memon
6th Semester DPT

2.  The lymphatic system comprises of a network of
conduits called lymphatic vessels that carry a clear fluid
called Lymph unidirectionally toward the heart.
 It
was first described by Olaus Rudbeck and Thomas
Bartholin.
 Itincludes all the structures dedicated to the circulation
and production of lymphocytes i.e. spleen, thymus, bone
marrow and the lymphoid tissue associated with the
digestive system.

4.  The lymphatic system has multiple interrelated
functions:
1. Responsible for the removal of interstitial fluid from tissues.
2. Absorbs and transports fatty acids and fats as chyle from the
digestive system.
3. Transports WBCs to and from the lymph nodes.
4. The lymph transports antigen-presenting cells (APCs), such
as dendritic cells, to the lymph nodes where an immune
response is stimulated.

5.  Thestudy of lymphatic drainage of various organs is
important in diagnosis, prognosis, and treatment of
cancer.
 The lymphatic system → responsible for carrying
cancerous cells b/w various body parts in a process
called metastasis.
 Theintervening lymph nodes can trap the cancer cells
→if not successful in destroying the cancer cells →
become sites of secondary tumors.

6.  Divisions of the lymphatic system:
1. the conducting system and
2. the lymphoid tissue.
 The conducting system
carries the lymph
consists of tubular vessels i.e. the lymph
capillaries, the lymph vessels, and the right and
left thoracic ducts.
 The lymphoid tissue
primarily involved in immune responses
consists of lymphocytes and other white blood cells

7. 1. Lymphedema is the swelling caused by the accumulation
of lymph fluid,
Cause→lymphatic system damage or malformations.

It usually affects the limbs, though face, neck and abdomen
may also be affected.
◦ Some common causes of swollen lymph nodes include:
infections,
infectious mononucleosis, and
cancer→ Hodgkin's & non-Hodgkin lymphoma
metastasis of cancerous cells via the lymphatic system.

8. 1. Lymphangiomatosis is a disease involving multiple cysts
or lesions formed from lymphatic vessels.
2. Elephantiasis, infection of the lymphatic vessels cause a
thickening of the skin and enlargement of underlying
tissues, especially in the legs and genitals.
 It is most commonly caused by a parasitic disease known
as lymphatic filariasis.
3. Lymphangiosarcoma is a malignant soft tissue tumor.
4. Lymphangioma is a benign tumor occurring frequently in
association with Turner syndrome.
5. Lymphangioleiomyomatosis is a benign tumor of the
smooth muscles of the lymphatics that occurs in the lungs.

9.  The spleen has important roles in regard to RBCs and the immune
system.
 Functions:
1. It removes old red blood cells and holds a reserve of blood in hemorrhagic
shock while also recycling iron.
2. As a part of the mononuclear phagocyte system → metabolizes hemoglobin removed
from erythrocytes.
3. It is one of the centers of activity of the reticuloendothelial system → analogous to a
large lymph node → absence leads to a predisposition toward certain infections.
 Red Pulp involved in the filtration of RBCs
 White Pulp involved in active immunity via hormonal & cell-mediated pathways
(antibodies)
 Composed of Malpighian corpuscles :
o "lymphoid follicles" → B-lymphocytes
o "periarteriolar lymphoid sheaths" (PALS) → T-lymphocytes

10.  It is secondarily involved in wide variety of systemic
diseases & its response causes its enlargement
(Splenomegaly).
 The disorders are classified on the basis of the degree
of the Splenomegaly characteristically produced & is
given in the next slides:

11. 1. Chronic myeloproliferative disorders:
1. Chronic myeloid leukemia
2. Myeloid metaplasia with myofibrosis
2. Chronic lymphocytic leukemia
3. Hairy cell leukemia
4. Lymphomas
5. Malaria
6. Gausher disease
7. Primary tumors of spleen(Rare)

12. 1. Chronic Congestive Splenomegaly
1. Portal HTN or
2. Splenic Vein obstruction
2. Acute Leukemias (inconsistent)
3. Hereditary Spherocytes
4. Thalassemia major
5. Autoimmune hemolytic anemia
6. Amyloidosis
7. Neimann-Pick disease
8. Langerhans histiocytes
9. Chronic splenitis
10. Tuberculosis, Sarcoidosis,Typhoid
11. Metastatic carcinoma or sarcoma

13. 1. Acute splenitis
2. Acute splenic congestion
3. Infectious mononucleosis (EBV induced)
4. Miscellaneous Acute Febrile disorders
 Septicemia
 SLE
 Intra-abdominal infections

14.  Hypersplenism → a state associated with many
diseases affecting spleen
Characteristics → removal of excessive numbers of
one or more of the formed elements (blood) resulting
into → Anemia, Leukemia, or Thrombocytopenia.
 Thrombocytopenia is more prevalent & severe.

15.  The thymus is a central lymphoid organ of the immune
system.
 Functions
1. T cells that attack the body's own proteins are eliminated in
the thymus through programmed cell death (apoptosis).
2. Provides an inductive environment for development of T-
lymphocytes from hematopoietic progenitor cells(T-cell
differentiation ).

16. Normal Thymus

17.  Thymus is involved in Lymphomas (particularly
those of T-cell lineage).
 The most frequent thymic disorders are:
1. Thymic hyperplasia
2. Thymoma

18.  Associated with the appearance of Lymphoid follicles/germinal
centers(containing reactive B-cells) within the medulla.
 Thymic follicular hyperplasia is present in those with Myasthenia
gravis, SLE, RA.
 Hyperplastic thymus removal is often beneficial early in the
disease.

19.  Tumors in which the epithelial cells constitute the neoplastic
elements.
 Characteristics → Presence of abundant precursor T-
cells(thyrocytes).

20. 1. Benign or Encapsulated thymoma which is cytologically & biologically
benign.
2. Malignant thymoma
 Type-I:
 cytologically benign but biologically aggressive & capable of local
invasion.
 Type-II (Thymic Carcinoma):
 cytologically malignant with all of the features of cancer & comparable
behavior.

21. Benign or Encapsulated_thymoma

22.  Malignant more than the benign
 Occur at any age but typically in Middle adult life
 30% Asymptomatic
 15-20 % with Myasthenia gravis have a thymoma
 Tumor removal often leads to the improvement in Neuromuscular disorder
 30-40% produce Local manifestations
 Mass demonstrable on CT Scan in the Anterosuperior mediastenum associated
with Cough, Dyspnea, & Superior Vana Caval Syndrome.
 The remainder were associated with some systemic disease (Myasthenia gravis).
 Associations with thymoma are:
◦ Hypogammaglobulinemia, SLE, Pure red cell aplasia, & nonthymic cancers

23. CT scan of the chest revealing a large necrotic mass in the left anterior
mediastinum (indicated by the red line).

24.  Usually fleshy, obviously invasive masses sometimes accompanied by metastases
to sites as the lungs.
 Most resmeble poorly/well-differentiated SCCs.
 Next most common malignant pattern → Lymphoepithelium-like carcinoma
 Composed of anaplastic cortical-type epithelial cells mixed with large
numbers of benign lymphocytes.
 Most common in Asian populations
 Sometimes contain EBV genome(member of Herpes virus family) →B-cell
polyclonal activation & proliferation

25. Locally invasive circumscribed thymoma
(Malignant Type-I)

26.  Thymomas → lobulated, firm, gray white masses, 15-20cm longest in dimension
 Most appear Encapsulated
 20-25% with apparent penetration of the capsule & infiltration of perithymic
tissues & structures
 All thymomas made up of a mixture of epithelial cells & a variable infiltrate of non-
neoplastic thymocyte

27. Mediastenum Thymoma Type A Spindle Cell 6

28.  Benign thymomas (medullary thymomas):
spindled or elongated epithelial cells resemble those that normally
populate the medulla
 Mixed thymoma
an admixture of the plumper, rounded, cortical-type epithelial cells
Medullary & Mixed patterns → 60-70% of all thymomas.
 Malignant thymoma type-II (Thymic Carcinoma)
Cytologically malignant accounting for 5% thymomas

29.  Malignant thymoma type-I
 Cytologically bland but locally invasive tumor(Ocassionally metastasize)
 20-25% of all thymomas
 Critical distinguishing feature → penetration of the capsule & the invasion of
sorrounding structures
 Neoplastic epithelial cells often from palisades around blood vessels →
spindled epithelial cells present sometimes
 Composed of varying proportions of the Epithelial cells & Reactive
thymocytes
 Epithelial cells resemble those found in the Cortex & are with abundant
cytoplasm & rounded Vesicular nuclei.