Diagnosis: Primary cutaneous mucinous carcinoma ( Mucinous sweat gland carcinoma, mucinous eccrine carcinoma)
Comment It is fairly easy to make a diagnosis from what you see on the slide.
Simple correct diagnosis is: Mucinous adenocarcinoma in the dermis.
Next question is: Is it metastatic or primary?
Reasonable answer is metastatic adenocarcinoma, probably from a primary adenocarcinoma from any internal organs that has the ability to metastasize to skin. A thorough clinical and radiological investigation may exclude a primary adenocarcinoma in internal organs. A diagnosis of metastatic adenocarcinoma in skin is part of systemic metastasis with grave prognosis. But a primary mucinous dermal adenocarcinoma, usually of sweat gland origin is locally aggressive but usually not prone to metastasis. In absence of any source of metastasis to skin, in this case next choice is a primary cutaneous mucinous carcinoma.
•Primary mucinous carcinoma of the skin (PMCS) is a rare, malignant neoplasm, most commonly occurring in the periorbital area. Differential diagnosis always include dermal metastasis from mucinous adenocarcinoma of other sites, such as, breast, lung, gastrointestinal tract, ovary etc.
•Primary mucinous carcinoma of the skin (MCS) is considered a primary eccrine sweat gland carcinoma.
• Microscopic: Nests of tumor cells separated from pools of mucin by fibrous septae. Cells have a round to cuboidal nucleus, a prominent nucleolus and abundant eosinophilic cytoplasm.
•Histochemically the mucin produced by the tumor is periodic acid-Schiff (PAS) and colloidal iron positive, but is resistant to hyaluronidase and diastase.
•Immunohistochemistry : Tumor cells are positive for cytokeratins, vimentin, EMA, S-100 protein, CEA, estrogen and progesterone receptors.
•Primary mucinous carcinoma of the skin typically has an indolent course with local recurrene but rare metastasis.
Deba P Sarma, MD, Omaha