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“Onycholemmal Carcinoma.” An Unusual Case With Apocrine and Sebaceous Differentiation. Are These Tumors a Microcystic Nail Bed Carcinoma?

Perrin, Christophe MD*; Kettani, Sami MD; Ambrosetti, Damien MD*; Apard, Thomas MD; Raimbeau, Guy MD§; Michiels, Jean-François MD*

American Journal of Dermatopathology: July 2012 - Volume 34 - Issue 5 - p 549–552
doi: 10.1097/DAD.0b013e31823fd8e4
Extraordinary Case Report

Abstract: Subungual malignant epithelial tumors with tricholemmal keratinization have rarely been described as “malignant proliferating onycholemmal cyst” and “onycholemmal carcinoma (OC).” We report an additional case of a slow growing OC occurring on the middle finger of a 58-year-old man, which was unusual as it showed sebaceous–apocrine differentiation, in addition to a nail bed carcinoma with tricholemmal microcysts. We therefore consider the descriptive term of microcystic nail bed carcinoma more appropriate than OC. It is recognized that none of the rare cases of OC meet the classical additional criteria proposed by Headington for tricholemmal carcinoma, that is, lobular arrangement, peripheral palisading, thickened basement membrane, and glycogen-positive tumors cells. On the other hand, we suggest that the term follicular microcysts of the nail bed should be retained to describe the true nature of subungual epidermoid inclusions, which show usually a limited differentiation toward the follicular isthmus. Therefore, the previous cases of OC without sebaceous–apocrine differentiation could be best classified as a microcystic nail bed carcinoma arising from the follicular microcysts of the nail bed, with a limited differentiation toward the keratinization of the follicular isthmus.

*Laboratoire Central d'Anatomie Pathologique, Hôpital Pasteur, University of Nice, Nice, France

Centre d'Anatomie pathologique, Angers, France

Hôpital privé Saint Martin, Centre de chirurgie de la Main, Caen, France

§Centre de la Main d'Angers, Angers, France.

The authors declare no conflicts of interest.

Reprints: Dr Christophe Perrin, MD, Laboratoire Central d'Anatomie Pathologique, Hôpital L. Pasteur, 30, Av voie Romaine, BP69, 06002 Nice CEDEX 1, France (e-mail: xst.perrin@bbox.fr).

© 2012 Lippincott Williams & Wilkins, Inc.