Melanoma metastases - pancreatic and perirenal space

Case contributed by Dr Bruno Di Muzio

Presentation

Left flank pain.

Patient Data

Age: 50 years
Gender: Male

There is a rounded solid mass within the anterior aspect of the pancreatic head, relatively hypovascular compared to the pancreatic parenchyma, and difficult to appreciate if intra or extra-pancreatic. Also, an amorphous solid enhancing mass is appreciated within the left kidney perirenal space. The liver has features of fatty infiltration, but no focal lesions. The remainder of the abdomen is unremarkable. 

When first assessing the scan, those findings guide us towards differential for malignancies and, given the distribution in different organs, favoring metastatic disease. The perirenal lesion has a differential with lymphoma, although it would be expected to be more hypodense in this case. The pancreatic lesion could represent a pancreatic adenocarcinoma, but the roundness/nodularity make it a little atypical.  

This patient came to have a known history of treated melanoma one year prior. 

Endoscopic ultrasound was performed and the pancreatic lesion approached: 

Microscopy: The smears show clusters of discohesive atypical epithelioid cells with prominent nucleoli and variable nuclear to cytoplasmic ratio. Occasional intra-nuclear inclusions are seen. Occasional cells appear binucleate. Pigment is not seen. Morphology is in favor of a metastatic melanoma, however, cell block is required for immunoperoxidase confirmation.

Cells are immunoreactive with S100 and Melan-A in keeping with a metastatic melanoma.

Macroscopy:  Endoscopic ultrasound-guided FNA of peripancreatic head lymph node - 2 alcohol-fixed smears + formalin-fixed needle cores received. Cellblock prepared.

Conclusion: Ultrasound-guided fine needle aspirate of peripancreatic head lymph node–malignant.

Therefore, both lesions were considered to represent metastatic melanoma. 

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