A Rare Case of Oral Malignant Melanoma with Gastrointestinal Metastases

Abstract

Introduction: Mucosal melanoma can develop from melanocytes located anywhere along the mucosal membranes lining the respiratory, gastrointestinal, or urogenital tract. It is a rare condition that accounts for less than 1% of all forms of melanoma. We present a patient with oral malignant melanoma who complained of abdominal pain and vomiting, and found to have metastases to the upper gastrointestinal tract during endoscopy. Case: A 65-year-old African American male with HIV (CD4 count of 403; viral load < 40 copies/mL) initially referred to oral surgery with the complaint of gingival swelling. His oral examination revealed a large 2.0 x 1.7 cm mobile area of dark pigmented gingival tissue in the left lower quadrant of the mouth. The excised area was histologically confirmed as mucosal malignant melanoma. Cross-sectional imaging of the head, neck, and chest revealed a lesion in the left ventral pons, enlarged left level 1 lymph node, and 7.5mm nodule in the right upper lobe of the lung; concerning for metastatic disease. After a multidisciplinary conference, the patient underwent palliative left hemi-mandibulectomy with bilateral neck dissection and radiation. Five months later, he was admitted for vomiting, abdominal pain, and weight loss. Repeat CT imaging revealed new metastases to his spleen, liver, and pelvis. The upper endoscopy revealed innumerable, non-obstructing black pigmented lesions and ulcers throughout the stomach and duodenum. Histopathology and immunohistochemical staining of the gastric biopsies were positive for Mart-1 and HMB-45 supporting the diagnosis of metastatic malignant mucosal melanoma. At six months from initial diagnosis, the patient unfortunately passed away on hospice care. Discussion: Mucosal malignant melanoma is a rare, but an aggressive form of melanoma. Compared to cutaneous and ocular melanoma, mucosal melanoma carries the lowest 5-year survival rate. Early diagnosis remains difficult given that these lesions tend to occur in occult sites without any early signs or symptoms. This clinical vignette illustrates a rare case of extensive gastrointestinal metastases from an oral malignant melanoma.Figure 1Figure 2Figure 3