Updates on the Pathology and Management of Nail Unit Tumors and Dermatoses

Examination of the nails: Main signs

Understanding the anatomy of the nail apparatus is a prerequisite for diagnosing and managing various nail disorders. The latter may be associated with systemic pathologies, or accompany infectious, inflammatory, tumoral, toxic or traumatic dermatoses. Before attempting to identify the cause, a rigorous clinical examination should be conducted to screen for elementary lesions that may affect general nail shape, nail surface, subungual attachments, periungual soft tissue or nail color. All of these guide differential diagnosis.

Update on nail unit histopathology

Histopathologic evaluation of the nail unit is an essential component in the diagnosis of nail unit disorders. This review highlights recent updates in nail unit histopathology and discusses literature covering a wide range of nail disorders including melanoma/melanocytic lesions, squamous cell carcinoma, onychomatricoma, onychopapilloma, onychomycosis, lichen planus, and other inflammatory conditions. Herein we also discuss recent literature on nail clipping histopathology, a useful and noninvasive diagnostic tool that continues to grow in popularity and importance to both dermatologists and dermatopathologists.

Diagnosis and surgical treatment of benign nail unit tumors

Little is known about benign non-melanocytic nail tumors, probably due to their low pathogenicity. They are commonly misdiagnosed as inflammatory or infective diseases. They have various features, depending on the type of tumor and its location in the nail apparatus. The typical sign of a tumor is the presence of a mass and/or secondary nail changes from damaged nail structures. In particular, if a single digit is affected by a dystrophic sign or a symptom is reported without any explanation, the presence of a tumor should always be ruled out. Dermatoscopy helps to enhance visualization of the condition and in many cases supports the diagnosis. It may also assist in identifying the right place to biopsy, but it never replaces surgery. Most common non-melanocytic nail tumors are analyzed in this paper, including glomus tumor, exostosis, myxoid pseudocyst, acquired fibrokeratoma, onychopapilloma, onychomatricoma, superficial acral fibromyxoma and subungual keratoacanthoma. The aim of our study is to review the main clinical and dermatoscopic characteristics of the most common benign non-melanocytic nail tumors, to correlate them with the histopathology and to advise practitioners of the best surgical management.

Immunohistochemistry for Preferentially Expressed Antigen in Melanoma in the Differential Diagnosis of Melanocytic Lesions of the Nail Apparatus

ABSTRACT

Nail unit melanocytic lesions present a unique set of diagnostic challenges because of the unfamiliarity with clinical assessment and the lack of experience with histologic examination. Because the first surgical specimen received in the pathology laboratory is typically small, sometimes suboptimal biopsy, the distinction between melanoma and its histologic mimics can be difficult. For this reason, there has been a continued interest in the development of ancillary markers that may assist in the differential diagnosis of nail unit melanocytic lesions. Upregulation of preferentially expressed antigen in melanoma (PRAME) has been reported to be a common event in melanomas, and PRAME immunohistochemistry has been shown to be helpful in evaluating various melanocytic neoplasms. In this study, we evaluated PRAME protein expression in a series of nail unit melanocytic lesions. Twenty-five nail unit melanomas (including small biopsy and amputation specimens) and 32 control benign melanocytic lesions were retrospectively retrieved. Nuclear PRAME staining was scored as percentage and intensity labeling. All melanoma cases showed the nuclear expression of PRAME, which was usually diffuse and strong. In specimens where the neoplastic cells are limited in number, the staining was restricted to the tumor cells, corresponding to the initial H&E impression. All control cases were negative for PRAME expression. PRAME expression is helpful in distinguishing between melanomas and other nail unit melanocytic lesions. This antibody also proved to be diagnostically valuable in detecting melanoma cells in small specimens with minimal disease.