Lung tumours comes to pathology to get diagnosed.
This article deals with the surgical pathology (core biopsies, lung resections). Pulmonary cytopathology is dealt with in the pulmonary cytopathology article.
An introduction to lung pathology is found in the pulmonary pathology article.
Lung tumours overview
Schematic overview of lung cancer (clinical)
- NSCLC = non-small cell lung cancer.
- SCLS = small cell lung cancer.
Basic pathologic approach to lung cancer
- LCLC = large cell lung cancer.
- SCLS = small cell lung cancer.
- Most lung cancer fits into one of the above categories.
- All types may be metastatic. Pathologists usually don't have to sort this out, as the clinican often knows whether a given lesion is metastatic (when correlated with radiology).
- Lung cancers may have a mixed morphology, e.g. SCLS may have squamous component.
- Categorization as non-small cell lung cancer (NSCLC) should be avoided, as treatment is now somewhat dependent on subcategorization.
Major types (primary)
- Adenocarcinoma is the most common (primary lung cancer).
- Adenocarcinoma is the non-smoker tumour - SCLC and squamous are more strongly associated with smoking.
- Most common lung tumour in children: metastasis (80-85% of lung tumours in children
- Distribution - think about the location of letters in mnemonic ASSL.
- Adenocarcinoma is usually periperal, i.e. smaller airways.
- Squamous cell carcinoma and small cell carcinoma are typically central.
Margins in lung
Margin in pneumonectomy specimens include:
- Vessels (artery, vein).
- Airway (bronchus).
- Soft tissue (lymphatics, fibrous tissue and lymph nodes).
- The traditional teaching is there are only hollow structure margins (artery, vein, airway) - yet the bronchial margin has been divided into mucosal and extramucosal.
- Peribronchovascular soft tissue involvement is a poor prognosticator but not an independent predictor if considered within the TNM staging.
Management of primary lung cancer
Management in the past was determined by categorization into:
- Small cell cancer.
- Non-small cell cancer (includes adenocarcinoma, squamous cell carcinoma, large cell carcinoma).
Microscopic features overview
- Glands or cytoplasm with mucin.
Squamous cell carcinoma
- Distinct cell borders with intercellular bridges.
- Eosinophilic cytoplasm.
Small cell carcinoma
- Very cellular.
- Large NC ratio - very small amount of cytoplasm.
- Cells fragile - they tend to look "smudged" (Azzopardi phenomenon).
There is a great review paper by Jagirdar.
Small cell carcinoma
- CD56 - cytoplasmic.
Squamous cell carcinoma
Primary vs. secondary
- TTF-1 is considered useful.
- 75% +ve adenocarcinoma
- 11% +ve SSC
- 50% +ve large cell carcinoma
- 0% +ve mesothelioma
- significant rates of +ve in some metastatic tumours -- see article by Jagirdar.
- TTF-1 - should be nuclear staining; cytoplasmic staining is non-specific.
- This is a group of tumours that has benign (e.g. carcinoid tumour of the lung) to malignant (e.g. small cell lung carcinoma) behaviour.
- They are thought to arise from pulmonary neuroendocrine cells.
The grouping can be divided into four types:
- Small cell carcinoma.
- Large cell neuroendocrine carcinoma.
- Typical carcinoid.
- Atypical carcinoid.
Cytologic features useful for differentiation:
- Small cell carcinoma: necrosis, scant cytoplasm, mitoses.
- Typical carcinoid: often more cytoplasm, no necrosis, low mitotic rate (MIB1: scant staining).
- Atypical carcinoid: higher mitotic rate/MIB1 than typical carcinoid, no necrosis.
- Large cell and small cell tumours behave in a similar fashion; large cell can be considered a morphological variant of small cell.
- 9/10 of carcinoids are typical and usually have a good prognosis, i.e. do not metastasize.
- Central location (vis-a-vis peripheral location) tends favours typical carcinoid over atypical carcinoid.
Adenocarcinoma of the lung
- AKA lung adenocarcinoma.
- Abbreviated BAC.
Squamous cell carcinoma of the lung
Small cell carcinoma of the lung
Non-small cell lung carcinoma
- AKA poorly differentiated carcinoma of the lung.
Adenosquamous carcinoma of the lung
- AKA pulmonary metastasis.
Atypical alveolar hyperplasia
Atypical carcinoid lung tumour
- AKA atypical carcinoid tumour of the lung.
Solitary fibrous tumour of the pleura
Pulmonary apical cap
A lesion that can mimic a lung neoplasm.
Pulmonary carcinoid tumourlet
- AKA carcinoid tumourlet.
Typical carcinoid lung tumour
Clear cell sugar tumour of the lung
- AKA clear cell sugar tumour.
- Abbreviated CCST.
- Lung - introduction to the lung, includes a basic approach.
- Medical lung disease.
- Missed endobronchial biopsy.
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