HMB45/PRAME, a Novel Double Staining for the Diagnosis of Melanocytic Neoplasms: Technical Aspects, Results, and Comparison With Other Commercially Available Staining (PRAME and Melan A/PRAME)

Abstract

PRAME (PReferentially expressed Antigen in MElanoma) is a tumor-associated antigen that was recently found to be expressed by malignant melanocytic lesions but not by benign ones, thus resulting useful in this diagnostic field. PRAME could also be expressed by some normal tissues and nonmelanocytic tumors, suggesting as caution should be adopted to use PRAME as a "pan-melanoma" marker for the differential diagnosis with other malignant tumors. Until now, PRAME expression was exclusively investigated through single staining with a monoclonal antibody targeting PRAME and with double staining for Melan A/PRAME found to be useful in specific diagnostic sets. Herein, we studied the expression of PRAME in 40 melanocytic lesions and 23 nonmelanocytic ones using PRAME, Melan A/ PRAME, and novel double staining for HMB45/PRAME. Although our results need to be validated, they support the adoption of HMB45/PRAME, alone or in combination with PRAME and Melan A/PRAME, as a helpful marker in the diagnosis of melanocytic neoplasms with a high concordance rate between primary melanoma and corresponding metastases.

PRAME Immunocytochemistry for the Diagnosis of Melanoma Metastases in Cytological Samples

“…As neoplastic cells may be scant in a cytological sample, it is important to choose the best ICC markers. PRAME has recently emerged as a novel immunohistochemical marker useful for the differential diagnosis of melanocytic neoplasms [9][10][11]. Lezcano et al have recently demonstrated that up to 94% of CMs show diffuse immunopositivity for PRAME, while benign nevi were negative, or only focally positive [12].…”

Cutaneous Melanomas: A Single Center Experience on the Usage of Immunohistochemistry Applied for the Diagnosis

“…Besides, PRAME is expressed in many other tumors (germ cell tumors of the testis, lymphomas, peripheral nerve sheath tumors, ovarian carcinomas, etc.) but not in the majority of desmoplastic cM (one of the most challenging melanocytic lesions), and we already suggested great caution before the adoption of PRAME as a “pan-melanoma” marker [ 96 , 97 , 98 , 99 , 100 , 105 , 106 , 107 ]. We recommend using PRAME in conjunction with DS, adopting a melanocytic marker (HMB-45 or MART-1) only in appropriately selected diagnostic settings and integrating this result with the histologic exam, other immunohistochemical analyses, and molecular techniques in “ really-difficult-to-diagnose ” melanocytic lesions.…”

“…As previously clarified (Chapter 2.2.2. ), our working group has recently developed two DS combining PRAME (nuclear) with HMB-45 and MART-1 (cytoplasmatic) that showed very encouraging results and became part of the immunohistochemical panels routinely used in our laboratory [ 56 , 107 ]. In our experience, these DS (HMB-45/PRAME and MART-1/PRAME) are particularly useful in the following diagnostic scenarios: (1) lesions almost exclusively junctional/intraepithelial (allowing us to not evaluate keratinocytes); (2) lesions with a high inflammatory infiltrate (allowing us to not evaluate lymphocytes); (3) differential diagnosis between NN and MM, especially in SLNB; (4) metastasis of unknown primary tumor and/or primary cutaneous tumor with undifferentiated morphology, especially with limited available histological material.…”

PRAME Expression in Mucosal Melanoma of the Head and Neck Region

“…3, 4). A single stain for PRAME was additionally performed in all cases of MM-H&N with <76% of PRAME-positive cells (negative according to Lezcano et al16) and the results were superimposable to those observed with double stain for Melan A/PRAME 35. The two incisional biopsies of MM-H&N were both positive only adopting the score of Raghavan et al30 (PRAME-positive cells: 70% and 65%, respectively).…”