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Expression of Melan-A in cutaneous granular cell tumours: a diagnostic pitfall.

Authors :
Van Winden VI
Wong DD
Wood BA
Filion P
Harvey NT
Source :
Pathology [Pathology] 2024 Feb; Vol. 56 (1), pp. 47-51. Date of Electronic Publication: 2023 Nov 01.
Publication Year :
2024

Abstract

Morphological overlap exists between cutaneous granular cell tumours (GCT) and malignant melanoma, with the melanocyte-specific markers HMB45 and Melan-A commonly used to support the diagnosis of melanoma. We recently encountered several cases of GCT in our practice showing strong expression of Melan-A. The aim of this study was to establish the prevalence of positive immunohistochemical staining for Melan-A and HMB45 in a series of unequivocal GCTs. We also aimed to assess the prevalence of staining for PRAME (PReferentially expressed Antigen in MElanoma), a marker expressed in >80% of primary melanomas as well as many non-melanocytic tumours. A total of 20 cutaneous/subcutaneous GCTs were evaluated using Melan-A, HMB45 and PRAME immunohistochemistry. Staining for Melan-A and HMB45 was scored using a semiquantitative scale from 0 (absent) to 3+ (staining present in >50% of tumour cells). PRAME expression was recorded as either positive (>75% of cell nuclei staining) or negative. Melan-A expression was observed in four GCTs (20%), with strong and diffuse (3+) staining seen in two cases (10%), both from anogenital areas. Weak patchy nuclear PRAME expression was seen in every case, interpreted to be negative. HMB45 was also negative in all cases (100%). Our study demonstrates that Melan-A expression can be strong and diffuse in a subset of otherwise unequivocal cutaneous GCTs, which may cause diagnostic confusion with malignant melanoma. HMB45 and PRAME did not stain any of the GCTs in our series.<br /> (Copyright © 2023 Royal College of Pathologists of Australasia. All rights reserved.)

Details

Language :
English
ISSN :
1465-3931
Volume :
56
Issue :
1
Database :
MEDLINE
Journal :
Pathology
Publication Type :
Academic Journal
Accession number :
37989630
Full Text :
https://doi.org/10.1016/j.pathol.2023.09.009