Melan-A-Positive Granular Cell Tumor With Extensive Intraneural and Perineural Spread: A Rare Case Report

TL;DR

A rare case of a Melan-A-positive granular cell tumor with extensive nerve spread is reported, highlighting its similarity to melanoma and diagnostic challenges.

Contribution

Presents a rare case of Melan-A-positive granular cell tumor with perineural spread and suggests immunohistochemical markers for diagnosis.

Findings

The tumor showed extensive perineural and intraneural spread with Melan-A positivity.

Immunohistochemical markers like Inhibin-α and PRAME are proposed for diagnosing Melan-A-positive GCTs.

The case highlights the importance of distinguishing GCTs from melanoma due to overlapping features.

Abstract

Cutaneous granular cell tumors (GCTs) are rare tumors that typically exhibit benign clinical behavior and are likely of Schwann cell origin. Some histologic and immunohistochemical variants of GCTs may present challenges due to infiltrative growth patterns, perineural invasion, and expression of Melan-A. In this case report, we present a 27-year-old male who had previously been diagnosed with a typical GCT on the back a few years ago. The current biopsy from the proximal palm demonstrated a cytologically similar tumor with extensive perineural spread and notable positivity for Melan-A. Although uncommon, these features are consistent with the histological appearances of GCTs. The current views on the histogenesis of GCTs, clinical associations, differential diagnosis with melanoma, and histological criteria for malignant GCTs are discussed. A panel of immunohistochemical stains, including Inhibin-α and preferentially expressed antigen in melanoma (PRAME), is proposed for use in rare instances of Melan-A-positive GCTs.

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