Occurrence of Pigmented Mucoepidermoid Carcinoma of the Parotid Gland in a Post-operated Case of Conjunctival Melanoma: A Diagnostic Challenge

The parotid gland mucoepidermoid carcinoma (MEC) is the most common primary malignant tumor of the salivary glands. Metastatic tumors of parotid account for approximately 25% of all cases. The commonest malignancies to spread to intraparotid lymph nodes are squamous cell carcinoma, followed by melanoma and, less frequently, cancers from the oral cavity. Usually, cutaneous melanoma in the head and neck area is the precursor of malignant melanoma in the parotid gland. However, the exact process underlying the existence of melanin pigment in salivary gland tissue is unknown. A 72-year-old woman with a history of conjunctival melanoma arrived at the otolaryngology outpatient clinic complaining of preauricular pain and swelling. It was a 1.5 × 1.5 cm lesion. Given the background, cytology revealed high-grade malignancy with pigmentation upon fine needle aspiration, which was suggestive of malignant melanoma. On Cellblock and immunohistochemistry, it was confirmed as pigmented MEC. This case underscores the importance of immunohistochemistry and CB preparation in both diagnosis and patient care. In pathology, the existence of melanin pigment is a fascinating phenomenon, and melanin pigment that causes lesions is not invariably a sign of malignant melanoma.