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Morphology of Lung Cancer

Carcinoma pulmonis

For medical students2 min readUpdated 2026-10-10

Lung cancer is a malignant epithelial tumor whose morphology depends on anatomical localization and histogenesis. Pathological anatomy distinguishes central (hilar) and peripheral growth patterns, as well as small cell and non-small cell variants requiring precise immunohistochemical verification.

Central carcinomaDevelops in large bronchi against the background of chronic inflammation
Peripheral carcinomaGrows distal to large bronchi, often forming in scars
SCLC markerCytoplasmic chromogranin A confirms neuroendocrine differentiation
Late stageMassive carcinoma is the ultimate outcome of both central and peripheral tumors

Histological Classification and Markers

Morphological verification of the tumor is based on histogenesis and immunohistochemical profile. There are two fundamentally different groups:

1. Small Cell Lung Cancer (SCLC) Characterized by pronounced neuroendocrine differentiation. Pathogenesis involves specific biomolecular markers: cellular oncogenes, tumor suppressor genes, and growth factors. Immunohistochemistry demonstrates pancytokeratins in more than 90% of parenchymal cells. Chromogranin A serves as a specific marker, visualized as granules in the cytoplasm of cancer cells, reliably confirming the neuroendocrine nature of the neoplasm.

2. Non-Small Cell Lung Cancer (NSCLC) Represents a heterogeneous group of tumors with diverse histogenesis. Main types:

For an accurate diagnosis, pathologists must perform careful differential diagnosis between adenocarcinoma and poorly differentiated squamous cell carcinoma.

Central (Hilar) Carcinoma

Central carcinoma develops directly within large bronchi. The pathological process usually manifests against a background of prolonged chronic inflammation.

Histogenesis and Precancerous Lesions The source of malignant growth is bronchial epithelial cells: basal, goblet, or ciliated cells. This is preceded by precancerous changes—squamous metaplasia and dysplasia of the bronchial epithelium.

Morphology and Growth Macroscopically, central carcinoma can present as a polypoid, nodular, branched, or mixed (nodular-branched) form. Histologically, it is most frequently squamous cell carcinoma or small cell carcinoma.

Complications Tumor growth is characterized by aggressive local invasion. Obstruction of the bronchial lumen leads to pulmonary complications: atelectasis formation and post-obstructive (retrostenotic) abscess development. Invasion extends into the mediastinum, pericardium, esophagus, and major vascular trunks. Ingrowth into large vessels is a critical condition, as it triggers massive pulmonary hemorrhage.

Intravital diagnostics utilize bronchoscopy with biopsy, sputum cytology, and radiological imaging.

Peripheral Carcinoma and Progression

Peripheral carcinoma is localized in the lung parenchyma, distal to the large bronchi.

Background and Precancerous Processes Similar to central carcinoma, chronic inflammation serves as the background; however, focal or diffuse fibrotic changes play a critical role here. Precancerous processes include:

Macroscopically, nodular and nodular-branched growth forms predominate.

Progression An essential rule of pathological anatomy: although the morphology of hilar and peripheral carcinomas differs in early stages, the late-stage development of both types converges into massive lung carcinoma.

Mnemonic

To remember NSCLC markers: Squamous cell — Low-molecular-weight cytokeratins (S-L), Adenocarcinoma — High-molecular-weight cytokeratins (A-H).

Frequently asked questions

What are the pathways and typical metastatic localizations of lung cancer?

Lung cancer metastasizes via lymphatic, hematogenous, and implantation pathways.

  • Lymphatic spread is the primary route. Initial metastases appear in regional lymph nodes of the lung root (bronchopulmonary, peribronchial), followed by involvement of bifurcation, paratracheal, mediastinal, and supraclavicular lymph nodes.
  • Hematogenous spread occurs in later stages. Typical target organs include the liver, bones, brain, adrenal glands, and the contralateral lung.
  • Implantation spread involves dissemination across serous membranes, leading to pleural, pericardial, and peritoneal carcinomatosis.
What specific immunohistochemical markers are identified in lung adenocarcinoma?

Lung adenocarcinoma reveals high-molecular-weight cytokeratins, mucin, surfactant, and other markers.

What paraneoplastic syndromes are caused by small cell lung cancer?

Small cell lung cancer can ectopically produce ACTH, while bronchogenic carcinoma can produce ACTH, parathyroid hormone-related protein, insulin, and glucagon. Ectopic ACTH production is associated with Cushing syndrome, and parathyroid hormone-related protein production causes paraneoplastic hypercalcemia.

How is the diagnosis of small cell lung cancer confirmed?

By the presence of neuroendocrine differentiation features. The primary immunohistochemical marker is chromogranin A, which is detected as granules within the cell cytoplasm.

What is "scar cancer"?

It is a developmental variant of peripheral lung cancer. It arises against a background of focal or diffuse sclerosis from areas of atypical epithelial hyperplasia within oval and slit-like structures.

What complications are characteristic of central carcinoma?

Obstruction of the bronchial lumen leads to atelectasis and post-obstructive abscesses. Tumor invasion into large vessels can cause profuse pulmonary hemorrhage.

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