What's Your Diagnosis? Metastatic Melanoma of Unknown Primary
Introduction. A 66-year-old man presented to the emergency department (ED) with mid and left upper quadrant abdominal pain and shortness of breath.
History. The patient had been complaining of coughing and increased shortness of breath with exertion that became progressively worse over 6 months. He had an episode of vomiting 2 days before arriving at the emergency department. He also complained of abdominal pain and cramping. His past medical history included lung and liver tumors, which were incidental findings on positron emission tomography-computed tomography (PET-CT) scans. The patient also had tobacco use disorder, however, he quit smoking in 1981. Other details of his smoking history are not known. The patient’s mother was previously diagnosed with myeloid dysplasia. There was no family history of skin-related cancer.
Diagnostic testing. Abdominal CT scan showed two large, ulcerated masses in the jejunum suspicious for malignancy as well as several enlarged mesenteric lymph nodes (Figure 1).
Figure 1. CT scan with oral contrast. Oral contrast-enhanced CT image of the abdomen shows enlarged mesenteric lymph nodes and ulcerated masses.
Pelvic CT scan showed a right iliac bone with irregular sclerotic and lytic areas. Colonoscopy also revealed significant wall thickening and dilation. Biopsy of the jejunal mass revealed a malignant neoplasm involving unremarkable small bowel mucosa (Figure 2).
Figure 2. Representative histological section of the jejunal mass biopsy (H&E stain).
The tumor cells were negative for cytokeratin (Figure 3) and strongly positive for melanocytic markers SOX10, S100, HMB45, and Melan A (Figure 4).
Figure 3. Immunohistochemistry for cytokeratin AE1/AE3 showed that the tumor cells were negative for cytokeratin.
Figure 4. Immunohistochemistry for melanocytic marker SOX10 revealed strong and diffuse positivity in tumor cells.
In situ hybridization was negative for a rearrangement involving the EWSR1 gene, excluding gastrointestinal clear cell sarcoma. The overall findings were diagnostic of stage IV (cTX(2), cN2b, pM1c) melanoma.
