A case of malignant melanoma of unknown primary origin in the submandibular lymph nodes

We report a case of malignant melanoma of unknown primary origin that was found in the submandibular lymph nodes. A 63-year-old man presented on April 19, 1996 because of a swelling in the right submandibular region. The lesion measured 48 × 38mm and had no spontaneous pain. We planned to perform an excisional biopsy for histological diagnosis, but the patient refused the operation because the lesion had shrunk to about one half of its maximal size. The patient was therefore followed up.By June 1997, the lesion had grown rapidly, measuring 60 × 50mm. We suspected a malignant lesion, probably malignant lymphoma, from the results of a computed tomographic scan and 67Ga scintigraphy. On July 3, 1997, we performed surgical excision and made a histopathological diagnosis of malignant melanoma with lymph node metastasis. However, there was no evidence of a primary lesion of malignant melanoma in the skin, mucosa, eyes, or digestive system.