Metastatic Amelanotic Malignant Melanoma of the Parotid Gland

Amelanotic malignant melanoma is a rare subtype, comprising only approximately 2-8% of all malignant melanoma. Amelanotic melanoma of the parotid gland is even more scarce and difficult to diagnose thus causing a diagnosis dilemma when encountered. In this case report, we highlight the importance of consideration of diagnosis of amelanotic melanoma in parotid gland malignancies which will ensure prompt investigation and treatment. We further discuss the challenges in diagnosing amelanotic melanoma and relevant clinical examination and investigation.

We report a rare case of metastatic malignancy of parotid gland in a 74-year-old gentleman who presented with a parotid mass and overlying skin changes. Initial histopathology reports pointed towards sarcoma and lymphoma which caused a delay in diagnosis. However, a thorough examination and PET CT which revealed hypermetabolic peri and intra parotid lymph nodes prompted early surgical intervention of total parotidectomy. Special immunochemistry staining including vimentin, HMB45 and CD56 revealed metastatic amelanotic malignant melanoma of parotid gland. The patient then underwent adjuvant oncological treatment and recovered well.

Although rare, metastasis to the parotid gland from a primary amelanotic melanoma should be considered one of the differentials in parotid gland tumours, hence the proposed investigations for early detection, prompt diagnosis and treatment to ensure a better prognosis and quality of life.