DP08 Clinical and histopathological features of pigmented epithelioid melanocytomas: a retrospective case series

Abstract

Pigmented epithelioid melanocytoma (PEM) is a rare, poorly understood skin tumour that mimics melanoma. Diagnosis relies on clinical and histopathological analysis. There is potential for regional lymph node involvement and rare visceral metastasis. We retrospectively analysed eight cases of PEM diagnosed in our region between May 2016 and August 2025. The median age at diagnosis was 47.5 years (range 17–72), and the cohort was predominantly female (female-to-male ratio 5 : 3). The extremities were the most common site (4 of 8, 50%). The mean lesion size was 7.3 × 5.5 mm, and the average duration of lesions was 8.75 months (range 1–36). Most PEMs were referred as urgent suspected cancer (n = 7, 88%). Two patients (25%) had a prior history: one of melanoma and one of blue naevus. Melanoma was the most frequent prehistology diagnosis (5 of 11, 45%), and melanocytoma was absent from clinical differentials. Histopathology confirmed PEM in all cases, showing heavily pigmented epithelioid and spindle melanocytes with abundant melanophages. Immunohistochemistry was conducted in 88% of cases, demonstrating positivity for S-100, HMB-45, melan-A and cyclin D1, alongside a low Ki-67. β-Catenin and PRAME were negative. Next-generation sequencing in one case revealed no significant findings. Two cases (25%) showed loss of cytoplasmic PRKAR1A expression; one patient underwent Carney complex screening, which was normal. Two patients (25%) had regional lymph node imaging, all of which were negative. All PEMs were surgically removed with a median margin of 2 mm (range 1–2). Most cases (n = 7, 88%) were discussed by a multidisciplinary team, with six cases (75%) undergoing wide local excision with a median margin of 10 mm (range 3–10). No recurrence or metastasis occurred during a mean follow-up of 20.4 months; one patient died of unrelated cardiac arrest. This series reinforces that PEM is rare and often misdiagnosed, and requires combined clinical–pathological assessment. Surgical excision remains the mainstay of management, and prognosis is favourable in the absence of meta­static disease.