Abstract:

Primary cutaneous mucinous carcinoma (PCMC) is a rare, indolent malignancy with age-standardized incidence of less than 0.1 per million. It most commonly involves the eyelid. Recurrence can be seen in 0-33% of cases; however, it is infrequent after complete excision. Mucinous neoplasms of the skin are far more likely to be metastases from sites like the breast or gastrointestinal tract and can appear histologically identical to PCMC. Hence, a careful review of history with radiologic assessment and appropriate use of immunohistochemistry is necessary. We describe a case of recurrent PCMC of the scalp, an uncommon site for this rare entity, despite prior complete excision. A 50-year-old male initially presented with a posterior scalp nodule which was diagnosed as PCMC after excluding metastases, clinically. The lesion was completely excised. The patient developed induration at his previous excision site 3 years later, which was clinically suspected as a scar versus recurrence needing another excision. Sections revealed a dermal/subcutaneous tumor with islands of uniform epithelioid cells suspended in mucin pools. Tumor cells were positive for CK5/6 and CK7 while negative for CEA and p63, consistent with recurrence of the patients known PCMC. The conventional surgical excision with frozen section evaluation yielded clear margins. The patient was subsequently lost to follow up. This case is an illustration of an unusual recurrence of a rare PCMC after complete excision. A coordinated effort from clinician, radiologist and pathologist is essential to diagnose PCMC.

Financial Disclosure:
No current or relevant financial relationships exist.

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Brandon Taylor, BS