Epithelioid melanocytic nevus with tubule and pseudoacini formation.

A 26-year-old female presented with a 7 mm irritated pink-red papule on the left posterior shoulder. A shave biopsy revealed a dermal proliferation of epithelioid cells arranged in small nests with central lumen-like structures resembling glands set in a densely sclerotic stroma. S100 and Melanoma antigen recognized by T cells 1 (MART-1) immunohistochemical positivity confirmed a dermal melanocytic neoplasm. Pan-cytokeratin and cytokeratin 7 were negative within the nests ruling out an adnexal neoplasm or metastatic adenocarcinoma. A Spitz nevus variant characterized by the presence of focal tubular structures (tubular epithelioid cell nevus) has rarely been described in the literature and is of uncertain biological significance. Similar structures have also been observed in Clark/dysplastic nevi and melanoma. Glandular differentiation is seen in a wide variety of benign and malignant epithelial neoplasms; however, melanocytes are not known to be capable of forming true glands. The exact mechanism and significance of this phenomenon are currently unknown. Certain postulations include central melanocyte apoptosis, autocrine or paracrine factor secretion or retraction artifact caused by tissue fixation. This distinctive finding is important to recognize in order to avoid misdiagnosis as a glandular neoplasm.
(© 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)