Clinically presumed primary malignant melanoma of the parotid gland with extensive cervical lymph node metastasis: a case report

BACKGROUND: Primary malignant melanoma of the parotid gland (PMMPG) is an exceedingly rare neoplasm, accounting for < 0.7% of all parotid malignancies. Differentiating it from metastatic melanoma to the parotid is clinically critical but diagnostically challenging. CASE PRESENTATION: A 62-year-old Chinese man presented with a 6-month history of a painless, enlarging left parotid mass. Extensive physical examination and imaging (CT and MRI) of the head, neck, and chest revealed no extraparotid primary lesion. Core needle biopsy and immunohistochemistry (S100+, HMB45+, MelanA+, Ki-67 ~ 50%) confirmed malignant melanoma. He underwent total parotidectomy with comprehensive neck dissection (levels I-V). The marginal mandibular branch was sacrificed because it was encased by tumor; other branches were preserved. Pathology confirmed a 32 × 25 × 23 mm melanoma with invasion into adjacent salivary tissue and metastasis in 14 of 48 cervical nodes; intraparotid nodes were negative. Postoperatively, the patient developed incomplete eyelid closure and lower lip weakness (planned nerve sacrifice plus traction neuropraxia). Adjuvant radiotherapy was advised, but the patient was lost to follow-up. CONCLUSIONS: Clinically presumed primary parotid melanoma should be considered in a parotid mass without an identifiable primary site. Complete surgical resection with appropriate neck dissection remains the mainstay. A high Ki-67 index and extensive nodal metastasis predict poor prognosis, underscoring the need for adjuvant therapy and close surveillance.