Metastatic Melanoma of the Tongue Base

Significance Statement

Metastatic melanoma of the upper aerodigestive tract is rare, and cases with metastatic melanoma of the tongue base are considered exceptionally uncommon. The prognosis of metastatic mucosal melanoma is extremely poor in the head and neck region. Herein, we reported the case of metastatic melanoma of tongue base with regional symptoms and was diagnosed through laryngoscopy.

Clinical Image

A 49-year-old man presented to our clinic with a lump sensation in throat for 1 month. He had primary cutaneous melanoma of the left big toe, T4bN2bM0, stage 3C; left big toe amputation and left inguinal lymph node dissection were performed 6 months ago. Subsequently, he received 12-week chemotherapy with Dacarbazine. Laryngoscopy revealed a large, nodular, dark-pigmented tumor with a smooth surface from the tongue base (Figure 1). Magnetic resonance imaging demonstrated an exophytic lesion of about 1.5 cm in diameter in the left vallecula region, which appeared hyperintense on T1-weighted and T2-weighted images (Figure 2). An excisional biopsy of the tongue base lesion was performed. Histopathology showed presence of melanin pigmented tumor cells within the submucosa having positive immunoreactivity to S100, HMB-45, and Melan-A and negative to CK. The Breslow thickness measured 12 mm at least. Neither junctional activity nor melanoma in situ was seen. Therefore, metastatic melanoma was confirmed (Figure 3). Then, he was referred to receive immunotherapy.

Figure 1.

Laryngoscopy view of the tongue base tumor.

Figure 2.

Magnetic resonance imaging demonstrated a hyperintense mass lesion (arrow) located in the left vallecula region on T1-weighted image (A) and T2-weighted image (B).

Figure 3.

Histopathological results of the tongue base tumor. A, Hematoxylin and eosin staining showed melanin pigmented tumor cells with nuclear pleomorphism and large eosinophilic macronucleoli but without junctional activity (×40 magnification). B, Immunostaining for HMB45 (×100 magnification). C, Immunostaining for Melan-A (×100 magnification). D, Immunostaining for S100 (×100 magnification).

Melanoma, a tumor produced by malignant transformation of melanocytes, can occur on the skin or may appear in other locations where neural crest cells migrate. Cutaneous malignant melanoma has a high lymphatic and blood spreading potential. Only 0.6% to 9.3% of patients with cutaneous malignant melanoma will have metastases to the mucosa of the upper aerodigestive tract. ¹ Cases with metastatic malignant melanoma of tongue or tongue base were reported scarcely, ^2,3 and they were rarely diagnosed by endoscopic approaches. Regional symptoms such as dysphagia, sensation of food sticking, or difficulty in swallowing are indicative early signs. Metastatic melanomas of tongue stands for a particularly poor prognosis. ³ Histopathologic description of tumor cells without junctional activity in the overlying or adjacent mucosa would help the physicians to distinguish metastatic disease from primary mucosal melanoma. ¹ Differential diagnosis of these 2 groups is beneficial to determine workup and therapeutic options. Definitive surgical resection is considered to be a gold standard for treatment of primary mucosal melanomas of head and neck region, ⁴ whereas combination of multiple treatment strategies including debulking procedure or palliative surgery is more suitable in those with metastatic disease. ⁵