Laryngeal mucosal malignant melanoma. A clinicopathologic, immunohistochemical, and ultrastructural study of four patients and a review of the literature.

BACKGROUND: Primary laryngeal mucosal malignant melanomas are uncommon tumors that morphologically are readily confused with more common types of laryngeal cancer.
METHODS: Four cases of primary laryngeal mucosal malignant melanoma were identified from the files of the Otolaryngic Tumor Registry-Armed Forces Institute of Pathology. Clinical records were available for all four cases. Paraffin blocks or unstained slides were available for three of the four cases. The light microscopic features were evaluated in all cases. Immunohistochemistry was performed in three cases; electron microscopic analysis was performed in two cases. Follow-up data was available in three of the four cases.
RESULTS: The patients were all males and ranged in age from 35 to 84 years. The clinical presentations included hoarseness, hemoptysis, dysphagia, and airway obstruction, with complaints ranging from 1 to 8 months. The sites of involvement included the supraglottic larynx and the right true vocal cord. A history of cutaneous melanoma or of a melanoma of another site was not reported for any of the patients. Histologically, the tumors were invasive and composed of a pleomorphic epithelioid cell population of malignant cells. Malignant spindle-shaped cell could also be identified. The presence of melanin was identifiable by light microscopy in two cases; Fontana stains confirmed the presence of melanin in the other two. The immunohistochemical findings showed diffuse immunoreactivity with S-100 protein and HMB-45. There was no immunoreactivity with cytokeratin. The specimen of one patient demonstrated focal immunoreactivity with chromogranin. Electron microscopic features included the presence of premalonosomes or melanosomes. Total laryngectomy was the treatment of choice supplemented with radiotherapy. Follow-up information was available for three patients and all three died of metastatic disease within 36 months of diagnosis. Metastasis occurred to the brain, lungs, spine, and regional lymph nodes. The fourth patient was lost to follow-up.
CONCLUSIONS: Laryngeal mucosal malignant melanoma is an uncommon neoplasm that clinically and pathologically simulates more conventional types of laryngeal cancers. The light microscopic, immunohistochemical, and electron microscopic findings confirm the diagnosis. Aggressive management is indicated, as these tumors disseminate widely and are rapidly fatal.