Pathology of Merkel Cell Carcinoma
The tumour cells express cytokeratin 20 which is characteristic of Merkel Cell Carcinoma.
Merkel cell carcinoma is a rare, neuroendocrine cancer of skin.
This tumour was
originally described under the name of "trabecular carcinoma" by Toker in
Histologically, the tumour cells are usually located in the dermis.
Purely intraepidermal in-situ
Merkel cell carcinoma has also been reported.
Often the intradermal tumour fills the entire dermis and is separated from
the epidermis by thin Grenz zone.
Glandular differentiation may be present.
Nuclei are uniform and some cells exhibit nuclear moulding.
The chromatin pattern is finely granular.
Small nucleoli may be present. Mitotic figures and apoptotic bodies are often numerous.
Histological variants include desmoplastic, epidermotropic and pagetoid
The main differential diagnosis of Merkel cell carcinoma are PNET, lymphoma, small cell melanoma, metastatic small cell carcinoma and squamous cell carcinoma.
Appropriate antibody panel may be helpful in the differential diagnosis of cutaneous "small round blue cell" tumour.
The panel includes Cytokeratin (CK), Cytokeratin 20, Neurofilament, S-100 protein, Epithelial membrane antigen (EMA) , carcinoembryonic antigen (CEA) ,Neuron-specific enolase NSE, CD99 and LCA.
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