A Diagnostic Conundrum: Amelanotic Vulvar Malignant Melanoma in a Postmenopausal Patient

Abstract

Amelanotic vulvar malignant melanoma is an exceedingly rare and aggressive malignancy, accounting for only 2% of vulvar melanomas and presenting unique diagnostic challenges due to its lack of pigmentation. This report discusses the case of a 57-year-old postmenopausal woman who presented with a 2x2 cm greyish-white growth on the labia majora, accompanied by itching and burning for three months. Clinical examinations and routine investigations were inconclusive, necessitating a biopsy for definitive diagnosis. Histopathological analysis revealed nests of atypical cells exhibiting high-grade features, including a high nuclear-to-cytoplasmic ratio, vesicular chromatin, prominent eosinophilic nucleoli, and mitotic activity. The absence of melanin pigment complicated the diagnosis, requiring immunohistochemical confirmation with markers such as S100, Melan-A, and HMB45. Differential diagnoses, including poorly differentiated squamous cell carcinoma, neuroendocrine tumor, and adenocarcinoma, were meticulously excluded through morphological and immunohistochemical evaluation. This case underscores the critical importance of histopathological examination and immunohistochemistry in accurately diagnosing vulvar lesions, particularly in amelanotic variants, where clinical presentation can mimic other malignancies. Given the high metastatic potential and poor prognosis of vulvar melanoma, early recognition, accurate diagnosis, and prompt surgical intervention, including wide local excision and lymphatic dissection, are essential. This case highlights the need for heightened clinical suspicion and a multidisciplinary approach in managing rare vulvar malignancies to optimize patient outcomes.