4. Principle of pulmonary metastasis
• Lung is a filter-like organ
– The venous return contains lymphatic fluid from the
body tissues flows into the lung
• Pulmonary metastasis is extremely common
• Incidence of metastases to lung parenchyma
– 20% to 54% of patients who died of malignancy
• The common primary organs are:
– Breast, colon, kidney, uterus, H&N
– Choriocarcinoma, osteosarcoma, testis, melanoma,
Ewing’s sarcoma, thyroid carcinoma
5. Pathogenesis of pulmonary metastasis
• 5 mechanisms
1. Pulmonary or bronchial artery
2. Lymphatics
3. pleural space
4. Airway
5. Direct neoplastic invasion
• Hematogenous spread--most common
– Most reach the arterioles and capillary beds
– Some survive and grow into the interstitium
6. Typical pulmonary metastasis
• Hematogenous
-> Random distribution
-> Multiple
-> Round-shaped
-> Variable-sized
• Diffuse thickening of the interstitium
(lymphangitic carcinomatosis)
7. Atypical pulmonary metastasis
• Unusual radiologic features of metastases
– Poorly-defined/irregulary-marginate nodules
– Cavitation
– Calcification
– Hemorrhage around the metastatic nodules
– Pneumothorax
– Air-space pattern
– Tumor embolism
– Endobronchial metastasis
– Solitary mass
– Dilated vessels within a mass
– Sterilized metastasis
8. Nodule
• The most common presentation of metastasis
• Spherical nodules of varying size
• Random or peripheral
• Basal portion of the lung
9. • Tumor cells hematogenously transferred to
the lung proliferate into the perivascular
interstitium
– > interstitial lesions: clear, smooth margins
• Tumors grow out of vessels into the
interstitium and alveolar air space
– > lung parenchymal lesions
Nodule
11. Comparison of HRCT to
histopathological characteristics
• Well-defined, smooth margins
– Expanding type
– Alveolar space-filling type
• Poorly-defined margins
– Alveolar cell type
• Irregular margins
– Interstitial proliferating type
12. Correlation between the histological
type of the primary tumor and the CT
appearance
• Well-defined smooth margin
– Expanding type
– Observed in most metastatic HCC
• Metastatic adenocarcinomas
– Poorly defined, either irregular or smooth margins
– alveolar cell type and interstitial proliferation type
• Irregular margins
– Metastatic squamous cell carcinomas
• Irregular margins
– Metastases after chemotherapy
15. Cavitation
• Incidence
– 4% in metastases
– 9% in primary lung cancer
• 70% are metastatic squamous cell carcinomas
• The most common primary organ
– Head and neck in males
– Genitalia in females
• Metastatic adenocarcinoma
– no statistically significant difference in the frequency of
cavitation between the two histologic types.
• Metastatic sarcoma
– Pneumothorax is a frequent complication
• Chemotherapy is known to induce cavitation
• Indeterminate mechanism
26. Pneumothorax
• A result of tumor necrosis
• In aggressive and necrotic tumors
– Osteosarcoma: most frequent—5-7% of cases
– Other sarcomas
• Necrosis of subpleural metastases produces a
bronchopleural fistula -> Pneumothorax
• 10 of 1,143 cases with a spontaneous
pneumothorax have been attributed
to a malignancy
• A spontaneous pneumothorax in a
patient with a sarcoma should raise
the possibility of occult pulmonary
28. Air-space pattern
• Metastases from an adenocarcinoma, breast and
ovary origin
– May spread into the lung along the intact alveolar
walls (lepidic growth)
– Also in BAC
• The radiologic features mimic pneumonia
– Air-space nodules
– Consolidation containing an air bronchogram
– Focal or extensive ground-glass opacities
– CT halo signs
30. Tumor embolism
• In small or medium arteries
• Diagnosis is difficult radiologically
– Multifocal dilatation and beading of the peripheral
subsegmental arteries
– Infarction: peripheral wedge-shaped areas of attenuation
– Large tumor emboli in the main, lobar, or segmental
pulmonary arteries
• Tumors frequently associated with pulmonary tumor
emboli
– Hepatomas, breast and renal cell carcinomas, gastric and
prostatic cancers, and choriocarcinomas
32. Endobronchial metastasis
• Rare
• Major airway in only 2% of cases
• Two possible routes
1. Directly on the bronchial wall
– Aspiration of tumor cells
– Lymphatic spread
– Hematogenous metastasis to the bronchial wall
-> polypoid lesion inside the bronchial lumen
2. Tumor cells in the lymph nodes or lung parenchyma that
surround the bronchus grow along the bronchial tree
-> intraluminal lesion
33. • Kidney, breast, and colorectal cancers
• The most common radiologic appearance
– Lobar atelectasis
RCC
Endobronchial metastasis
35. • Solitary metastasis without a history of
malignancy
– CT: 0.4%–9.0%
– Chest radiograph: 25%
• Solitary pulmonary nodules detected in
patients with extrapulmonary malignancies
– 46% proved to be a metastasis
Solitary metastasis
36. • The likelihood that a solitary nodule
represents a pulmonary metastasis
– varies according to the histologic type of the
primary tumor and the patient’s age
• The most frequent malignancies
– melanoma; sarcoma; and cancer of the colon,
breast, kidney, bladder, and testis
Solitary metastasis
37. Dilated vessels within mass
• Engorged tumor vessels
– Suggest hypervascularity
– Sarcoma
• Alveolar soft-part sarcoma
• Leiomyosarcoma
39. Sterilized metastasis
• After adequate chemotherapy
• Necrotic nodules with or without fibrosis and
without viable tumor cells
• Histologic confirmation is necessary
• Common: choriocarcinoma and testis
• Germ cell tumors can convert to a benign
mature teratoma after chemotherapy and
result in persistence of the masses
40. Benign Metastasizing Tumor
• Rare
• Generally originate from
– Leiomyoma of the uterus
– Hydatidiform mole of the uterus
– Giant cell tumor
– Chondroblastoma
– Pleomorphic adenoma of the salivary gland
– Meningioma
• Despite their metastatic spread, these tumors are
histologically benign.
• Indistinguishable from malignant tumors, however,
benign ones show very slow growth
42. Conslusion
• Radiological diagnoses--based on typical
findings
• Awareness of the spectrum of radiologic
manifestations in atypical pulmonary
metastases
• Presence of atypical radiologic features and
metastasis is suspected
– > tissue diagnosis is recommended