Poorly differentiated carcinoma of the lung
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Poorly differentiated carcinoma of the lung, also poorly differentiated lung carcinoma, is an unclassified lung tumour with features of small cell carcinoma and non-small cell lung carcinoma.
Categorically, it is grouped with non-small cell lung cancer.
General
- Should be used when the DDx is small cell carcinoma versus non-small cell carcinoma.
- Poorly differentiated carcinoma leaves the surgical options on the table.
Clinical:
- Radiologic findings should not be suggestive of a metastasis.
Microscopic
Features:
- Small cell carcinoma/basaloid squamous cell carcinoma-like tumour.
DDx:
- Lung metastasis - history and imaging important.
- Small cell carcinoma of the lung.
- Squamous cell carcinoma of the lung.
IHC
- Lack of staining with neuroendocrine markers (chromogranin A -ve, synaptophysin -ve, CD56 -ve).
- Keratins +ve.
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Lung, Left Lower Lobe, Core Biopsy: - POORLY DIFFERENTIATED CARCINOMA, see comment. COMMENT: The tumour stains as follows: POSITIVE: EMA, AE1/AE3. NEGATIVE: TTF-1, chromogranin A, synaptophysin, CD56, CD45, CK5/6, p63. The morphology would be compatible with small cell carcinoma or basaloid squamous cell carcinoma. The neuroendocrine markers (chromogranin A, synaptophysin, CD56) and the squamoid markers available (p63, CK5/6) are negative; thus, the tumour is not further classified.