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

A case report of onycholemmal carcinoma in a 61-year-old Chinese male

Onycholemmal carcinoma is characterized as a slowly progressing malignant tumor originating from the epithelium of the nail bed. A limited number of cases have been documented in the English literature. The majority of the patients included in the reports underwent amputation of the affected phalanx, and no instances of recurrence were noted during the follow-up period. A 61-year-old Chinese male presented with a persistent ulceration on the nail bed of the right great toe. Microscopic analysis indicated the presence of an epithelial tumor consisting of small keratocysts with sudden central keratinization and atypical keratinocyte nests that were devoid of a granular layer. The tumor exhibited infiltrative growth within the dermis, displaying a multilobulated pattern, but did not extend into the distal phalangeal bone. Based on these findings, the diagnosis of onycholemmal carcinoma was made for this case. All documented cases indicate that onycholemmal carcinoma is a rare malignant tumor originating from the nail bed epithelium, and its clinical progression is typically slow and non-aggressive. This case is presented to provide an analysis of the clinical and pathological features of onycholemmal carcinoma, aiming to assist in the clinical selection of treatment options.

Basic Concepts in Nail Pathology

ABSTRACT

Understanding nail pathology is complex for general pathologists and even for those dermatopathologists who do not receive many nail samples in their laboratories. In this article, we attempt to review some of the primary entities in nail pathology with the aid of modern interpretations of nail histology and embryology. We also provide diagrams that can aid in comprehending this field of pathology.

Proliferating Onychomatricoma. Clinical, Dermoscopical, and Pathologic Features of Onychomatricoma New Variant Resembling Onycholemmal/Squamous Cell Carcinoma

Proliferating onychomatricoma is a new challenging variant of onychomatricoma that can clinically and histologically mimic squamous cell carcinoma/onycholemmal carcinoma. This is a retrospective case series study of the clinicopathologic and dermoscopic features of 6 patients with a pathologic diagnosis of proliferating onychomatricoma, which was conducted in the dermatology and dermatopathology departments of 2 university hospitals and a private nail's dermatology consultation. The clinical, histological, and immunohistochemical features and follow-up of 6 patients with proliferating onychomatricoma were analyzed; we compare our finding with 6 cases of conventional onychomatricoma. The female-to-male ratio was 1:1 with involvement of fingers in 4 and toe in 2. Among the symptoms were verrucous lesion simulating squamous cell carcinoma, nail thickening, periungual erythema, and pain; symptom duration ranged from 5 to 8 years. Clinical, dermoscopical en face free-margin view, and nail-clipping histologic findings reveal a nail wall-like pattern with pitting. Intraoperative, noncontact, polarizing, light dermoscopy was available in 1 case and showed the typical signs of onychomatricoma (OM). Histologically, all cases showed a well-differentiated, infiltrative, squamous, proliferative lesion exhibiting a lobulated and cystic pattern of growth in the dermis. Abrupt keratinization reminiscent of trichilemmal keratinization, but corresponding in fact to keratogenous spheres, was noted as well as a dysmaturative epithelial pattern. No atypical cytomorphological changes were found. Proliferating onychomatricoma is a new variant of onychomatricoma, which can be misdiagnosed as squamous cell carcinoma/onycholemmal carcinoma; its proper recognition may minimize morbidity associated with inappropriate treatment. Proliferating OM can be differentiated from conventional OM clinically by a free-edge wall-like pattern and on histology of nail clipping by the relatively small size of the cavities. Dermoscopic and nail clipping attributes as free-edge honeycomb-like cavities associated with conventional OM are well established and permit a diagnosis of OM without an invasive nail biopsy. The free-edge wall-like pattern is a distinct new dermoscopic and nail-clipping pattern that should raise for the others onychogenic neoplasms and prompt the clinician to obtain a biopsy specimen. In addition to proliferating OM, the differential diagnosis includes a micropapilliferum variant of OM, onychocytic matricoma, and onychocytic carcinoma.