We report 6 new cases of onycholemmal carcinoma, a rare, often misdiagnosed, subcategory of squamous cell carcinoma. All reported cases to date have been treated with amputation of the affected digit.

The purpose of this study was to present the clinical and pathological features of each new case and to discuss treatment options that spare digit functionality.

Hematoxylin-eosin stains were performed on tumor sections and examined using light microscopy. In situ hybridization using probes against human papillomavirus were examined in 1 case.

The female to male ratio was 1:1 with involvement of fingers in 3, thumb in 1, and toe in 1. Among the symptoms were onycholysis, periungual erythema, and pain; symptom duration ranged from 6 months to 2 years. Histologically, all cases showed a well-differentiated atypical infiltrative squamous proliferative lesion exhibiting a lobulated and cystic pattern of growth in the dermis. Abrupt keratinization reminiscent of trichilemmal keratinization was noted. Mohs micrographic surgery and radiation therapy were used as primary treatment modalities, maintaining digit functionality and achieving remission.

Limitations of this study included the small number of cases, the infrequency with which this tumor has been reported in the literature, and the inability to obtain follow-up on an older archival case.

Onycholemmal carcinoma is a distinct type of squamous cell carcinoma arising from the nail isthmus; its natural clinical course is indolent. In this regard less aggressive digit-sparing treatment modalities such as radiation or Mohs micrographic surgery should be considered.