Malignant melanoma with pseudoepitheliomatous hyperplasia of plantar region

Abstract

An 88－year－old woman presented with a melanocytic lesion in her right plantar region that had grown in size over 2 years. The initial examination revealed an 11 mm nodule with dark brownish－black and light－red keratinized areas. Due to concerns that the nodule might be a malignant melanoma, the nodule was excised with a 5 mm margin. Dermatopathological examination revealed atypical cells with melanin granules, nuclear atypia forming foci, and solitary infiltrates. The epidermis extended irregularly and with a reticulated pattern at the infiltration site. The atypical cells were positive for Melan－A, HMB45, and S－100 proteins, leading to a diagnosis of malignant melanoma with pseudoepitheliomatous hyperplasia (PEH). An additional 5 mm margin re－excision and sentinel lymph node biopsy of the right inguinal region were performed. Based on the findings, the tumor was classified as pT3aN0M0 Stage ⅡA. PEH can be induced by infections, tumors, or chronic inflammation/irritation, and often needs to be differentiated from squamous cell carcinoma. Therefore, recognizing the potential variability in clinical presentation remains crucial.[Skin Cancer (Japan) 2024 ; 39 : 242－246]