[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [General pathology](https://durgical.com/en/general-pathology/) › [Lung](https://durgical.com/en/general-pathology/areas/lung/) › Lung carcinoma: histologic types

# Lung carcinoma: histologic types

- Lesion

Four main types: adenocarcinoma is peripheral and glandular, squamous is central and keratinising, small cell is aggressive and neuroendocrine.

Updated Nov 12, 2026

## Key points

- Adenocarcinoma: about half of cases; commonest in women and never-smokers; peripheral; glands or mucin; TTF-1 and napsin A positive.
- Squamous cell carcinoma: about a fifth; strongly tied to smoking; central (hilar) bronchi; keratin pearls and intercellular bridges; p40 and p63 positive.
- Small cell carcinoma: about 15%; almost only in smokers; central; small cells with scant cytoplasm, salt-and-pepper chromatin, nuclear moulding; chromogranin, synaptophysin, CD56, high Ki-67.
- Large cell carcinoma: undifferentiated, no glandular, squamous or neuroendocrine features by morphology or IHC; distinct from large cell neuroendocrine carcinoma.
- Lepidic growth: tumour cells creeping along intact alveolar walls (adenocarcinoma in situ, minimally invasive adenocarcinoma).

## What it is

Lung carcinoma is the leading cause of cancer death worldwide. It is divided into small cell carcinoma and non-small cell carcinoma, the latter mainly adenocarcinoma and squamous cell carcinoma. The type decides molecular testing and treatment, so the pathologist confirms it with morphology and a small immunohistochemistry panel. Mixtures of types occur in the same tumour.

## Structure

- Gross: grey-white, firm to hard mass, sometimes with necrosis or hemorrhage; squamous tumours may cavitate.
- Adenocarcinoma: acinar, papillary, micropapillary, solid or lepidic patterns; mucinous variants spread through the airspaces and form satellite nodules.
- Squamous: sheets of cells with abundant eosinophilic cytoplasm, keratinisation and intercellular bridges; adjacent squamous dysplasia and carcinoma in situ.
- Small cell: sheets of small round to fusiform cells, frequent mitoses, extensive necrosis, crush artefact and the Azzopardi effect (DNA on vessel walls); neurosecretory granules on EM.
- Large cell: sheets of large cells with vesicular nuclei and prominent nucleoli.

## Step by step

- Carcinogens hit a wide field of bronchial and alveolar epithelium (field effect).
- Central airways exposed to heavy smoke develop squamous metaplasia, dysplasia and squamous carcinoma.
- Peripheral alveolar and bronchiolar cells progress through atypical adenomatous hyperplasia and adenocarcinoma in situ to adenocarcinoma.
- Neuroendocrine precursor cells with loss of TP53 and RB1 give small cell carcinoma, which spreads early.
- Tumours invade the bronchial wall, nodes, pleura and vessels and metastasise.

## The main types of lung carcinoma

| Type | Share | Location | Histology | IHC |
| --- | --- | --- | --- | --- |
| [Adenocarcinoma](https://durgical.com/en/conditions/lung-cancer/) | About 50% | Peripheral | Glands, mucin, lepidic edge | TTF-1, napsin A |
| [Squamous cell carcinoma](https://durgical.com/en/conditions/lung-cancer/) | About 20% | Central | Keratin pearls, intercellular bridges | p40, p63, CK5/6 |
| [Small cell carcinoma](https://durgical.com/en/conditions/lung-cancer/) | About 15% | Central | Small cells, moulding, necrosis | Chromogranin, synaptophysin, CD56, TTF-1 |
| Large cell carcinoma | Few percent | Any | Undifferentiated large cells | No specific lineage markers |

## Markers

- TTF-1
- Napsin A
- p40
- p63
- Chromogranin
- Synaptophysin
- CD56
- Ki-67

## Clinical notes

- Cough, weight loss, chest pain, dyspnoea and hemoptysis; many tumours are found late or on imaging of a nodule.
- Small cell carcinoma has usually spread at diagnosis and is treated with chemotherapy and radiotherapy; non-small cell tumours are resected when possible.
- Adenocarcinomas are tested for targetable alterations (EGFR, ALK, ROS1 and others) and PD-L1.

## Memory aid

Squamous and Small cell Sit centrally and both are Smokers' tumours; Adenocarcinoma is Away at the periphery.

## Test yourself

Think of the answer, then tap the question to see it.

## Which lung cancer type is most common in never-smokers?

Adenocarcinoma.

## Which immunohistochemical markers separate adenocarcinoma from squamous cell carcinoma?

Adenocarcinoma is TTF-1 and napsin A positive; squamous cell carcinoma is p40 (and p63) positive.

## What are the cytologic features of small cell carcinoma?

Small cells with scant cytoplasm, finely granular salt-and-pepper chromatin, inconspicuous nucleoli, nuclear moulding, many mitoses and necrosis.

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## Connections

## Related 7

- [Immunohistochemistry: the principle and the markers to know](https://durgical.com/en/general-pathology/immunohistochemistry-the-principle-and-the-markers-to-know/)
- [Differentiation and anaplasia: how a tumour cell looks under the microscope](https://durgical.com/en/general-pathology/differentiation-and-anaplasia-how-a-tumour-cell-looks-under-the-microscope/)
- [Naming tumours: -oma, carcinoma, sarcoma, and the misleading names](https://durgical.com/en/general-pathology/naming-tumours-oma-carcinoma-sarcoma-and-the-misleading-names/)
- [Lung carcinoma: pathogenesis and precursors](https://durgical.com/en/general-pathology/lung-carcinoma-pathogenesis-and-precursors/)
- [Lung carcinoma: spread and paraneoplastic syndromes](https://durgical.com/en/general-pathology/lung-carcinoma-spread-and-paraneoplastic-syndromes/)
- [Pulmonary neuroendocrine tumours](https://durgical.com/en/general-pathology/pulmonary-neuroendocrine-tumours/)
- [Pleural tumours: mesothelioma and solitary fibrous tumour](https://durgical.com/en/general-pathology/pleural-tumours-mesothelioma-and-solitary-fibrous-tumour/)

## Related conditions 2

- [Lung cancer](https://durgical.com/en/conditions/lung-cancer/)
- [Solitary pulmonary nodule](https://durgical.com/en/conditions/solitary-pulmonary-nodule/)

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Educational content on the mechanisms of disease; not a diagnostic or treatment guide and no substitute for a health professional's advice. No doses are given.

Sources: [Non–Small Cell Lung Cancer](https://www.ncbi.nlm.nih.gov/books/NBK562307/) (StatPearls (NCBI Bookshelf), 2025); [Small Cell Lung Cancer](https://www.ncbi.nlm.nih.gov/books/NBK482458/) (StatPearls (NCBI Bookshelf), 2025); [Lung Cancer](https://medlineplus.gov/lungcancer.html) (MedlinePlus, US National Library of Medicine, 2025).

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License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/general-pathology/lung-carcinoma-histologic-types/