Poorly differentiated carcinoma of the lung

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 carcinoma.

Categorically, it is group of 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.

Microscopic

Features:

• Small cell carcinoma/basaloid squamous cell carcinoma-like tumour.

DDx:

• Metastatic lung cancer.
• 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.

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. 

See also

• Lung tumours.