Track

Case Reports

Abstract

Immunohistochemistry for preferentially expressed antigen in melanoma (PRAME) is primarily utilized to evaluate melanocytic neoplasms. PRAME expression in non-melanoma skin cancer (NMSC) has not been extensively studied. Recent studies and reports indicate that PRAME is typically negative or rarely expressed with low intensity in NMSCs. We report a case of pagetoid squamous cell carcinoma in situ (SCCIS) with aberrant PRAME expression. A 75-year-old male with a history of multiple NMSCs presented with an erythematous dome-shaped papule on the central chest. A shave biopsy revealed several distinct cell populations including intra-epidermal neoplasia, dermal nevus, focal atypical melanocytic proliferation, solar lentigo, and actinic keratosis. Regarding the intra-epidermal neoplasm, there was extensive pagetoid scatter of atypical cells. These cells showed variable intensity nuclear staining and diffuse weak cytoplasmic staining with PRAME. The cells of interest were also positive for AE1/3, p53, p63, EMA, p16, and CK5/6, CK7 (patchy) and CK8/18 (focal), while negative for SOX10, Melan A, BerEP4, BRAF, GCDFP, HMB45, androgen receptor, ER, PR, CD5, mCEA, pCEA, BCL2, CD10, CD117a, CD34, and CK8. A diagnosis of pagetoid SCCIS with aberrant PRAME expression was made. Pagetoid SCCIS may histologically mimic melanocytic lesions, namely melanoma in situ. Diagnosis often requires immunohistochemical stains to correctly delineate between cell lineages. Our case highlights that PRAME is not specific to the melanocyte lineage and can show variable intensity expression in SCCIS. Additional stains should be utilized to help distinguish intraepidermal neoplasms exhibiting pagetoid scatter.