Abstract
Aims: We performed a single-center study to evaluate whether the data on the usefulness and possible limitations of PRAME could also be confirmed by our group. Methods: From 1 December 2021 to 29/03/2022 we collected 275 cases of melanocytic lesions that were immunostained with PRAME (Ab219650), rabbit monoclonal (Abcam). To better correlate PRAME expression with the nature (benign, uncertain potential for malignancy or malignant), we categorized PRAME tumor cells percentage positivity and intensity of immunostaining in a cumulative score obtained by adding the quartile of positive tumor cells (0,1 +, 2 +, 3 +, 4 +) to PRAME expression intesity in tumor cells (0,1 +, 2 +, 3 +). Results & Conclusions: Of these 275 lesions, 136 were benign, 12 were of uncertain potential for malignancy (MELTUMP or SAMPUS or SPARK nevus), and 127 were malignant. The immunoexpression of PRAME was totally negative in 125/136 benign lesions (91.9%) with only a few positive melanocytes (1+) with intensity 1+ in the remaining 11 cases (8.1%). Of the 127 cases of melanoma (histotype Superficial Spreading Type, Lentigo Maligna Type, Pagetoid type), PRAME was strongly positive in 104/127 cases (81.8%) with intensity 4+ and 3+. In 17 cases (13.3%, melanoma spindle and nevoid cell histotype) PRAME was positive in percentage 2+ and with intensity ranging from 2+ to 3+. In 6 cases (4.7%) of desmoplastic melanoma, PRAME was 1+ positive and / or completely negative. Of the 12 cases of spitzoid lesions with uncertain potential for malignancy, the immunoexpression of PRAME was much more heterogeneous and irregularly distributed throughout the lesion. These data are perfectly in agreement with the current literature, they demonstrate that the reliability of PRAME is quite high, but its use cannot disregard the morphological information and the execution of other ancillary immunohistochemical stains such as Melan-A, HMB-45, MiTF and SOX-10.
Financial Disclosure:
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