Case Number : CASE 4543 - 07 August 2024 Posted By: Admin_Dermpath

Merkel Cell Carcinoma

Small cell carcinoma from lungs is my first choice. we should rule out this one first - (a lung CT should do the trick). TTF1+ CK20- is not a regular immunophenotype for Merkel Carcinoma.

Agree with metastatic lung small cell carcinoma.

The TTF1+ CK20- immunohistochemical profile is commonly associated with lung adenocarcinoma, thyroid carcinomas, and small cell lung carcinoma.

Yes. Agree with mets Small Cell Carcinoma of the lung. 

On 11/08/2024 at 20:22, msofopoulos said:

Small cell carcinoma from lungs is my first choice. we should rule out this one first - (a lung CT should do the trick). TTF1+ CK20- is not a regular immunophenotype for Merkel Carcinoma.

Agree. IHC prolfile favors lung mets over MCC

Diagnosis: Neuroendocrine carcinoma with squamous differentiation and epidermotropism. 

The CK20 is focally positive, but in light of the diffuse TTF-1 and CK7 expression, I suggested to rule out metastasis from lung or other primary.  Radiology showed no lung masses.  The only finding was abnormal PET uptake in the left superficial parotid gland.  No biopsy from that site to date. 

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