Primary mucinous eccrine adenocarcinoma of the scalp: a case report.

Background Lesions of primary mucinous carcinoma of the skin present as painless, papular or nodular masses with sizes ranging from 5 mm to 120 mm. Metastatic deposits from undiagnosed visceral and breast adenocarcinoma are virtually indistinguishable microscopically from sweat gland carcinoma and must be considered before a diagnosis of sweat gland carcinoma is made. Case A 60-year-old woman presenting with a swelling over the scalp of 1 year's duration was clinically diagnosed to have a sebaceous cyst. Fine needle aspiration cytology of the lesion showed malignant cells in a mucoid background. Histologic examination of the excised mass revealed nests of tumor cells floating in pools of mucin in the dermis. Many of these nests showed tubular lumina. A diagnosis of mucinous eccrine adenocarcinoma was given. Conclusion Primary mucinous adenocarcinoma of the skin is a rare tumor and mimics metastatic adenocarcinoma. The scalp is the second common site for these tumors. Literature search regarding cytologic findings shows our case could be the second case reported so far.