Pancreatic metastasis of Merkel cell carcinoma and concomitant insulinoma: case report and literature review

Abstract

Background: Merkel cell carcinomas are rare neoplasm of neuroendocrine origin, usually observed in elderly people in areas with abundant sunlight, and predominantly located on the head and neck, extremities, and trunk. In many patients, a local recurrence after resection of the primary tumour and even distant metastases can be found.

Case presentation: We report an unusual occurrence of pancreatic metastases from a previously diagnosed Merkel cell carcinoma with the discovery of a concomitant insulinoma. An 82-year old lady suffered from recurrent attacks of hypoglycemia and presented with an abdominal mass, 2 years prior she had an excision done on her eyebrow that was reported as Merkel cell carcinoma. An extended distal pancreatectomy and splenectomy along with resection of the left flexure of the colon for her abdominal mass was carried out. Final histopathology of the mass was a poorly differentiated endocrine carcinoma in the pancreatic tail, in the peripancreatic tissue and in the surrounding soft tissue consistent with metastatic Merkel cell carcinoma in addition to an insulinoma of the pancreatic body.

Conclusion: This is the first documented case of a metastatic Merkel cell carcinoma and a concomitant insulinoma, suggesting either a mere coincidence or an unknown neuroendocrine tumor syndrome.

Figure 1

Computed tomography scan of the abdomen revealed a large lesion of 5 to 6 cm in relation to the pancreatic body and tail (venous phase A, B, arrows).

Figure 2

Arterial phase of the computed tomography scan of the abdomen shows a hypervascularized area (arrows) in the pancreatic body.

Figure 3

Merkel cell carcinoma on the right eyebrow.

Figure 4

Merkel cell carcinoma – primary tumor. A, B: Hematoxylin and eosin staining. A. Lower magnification showing intravasal tumor cells. B: Monomorphous tumor cells, pale staining nuclei, many mitotic figures. C: Strong cytokeratin 20 staining. Insert: Intravasal cytokeratin 20-positive tumor cells. D: Weak chromogranin A staining

Figure 5

Merkel cell carcinoma metastasis in the pancreas. A, B: Hematoxylin and Eosin staining. C: Synaptophysin staining. D: Cytokeratin 20 staining.

Figure 6

Insulinoma in the pancreatic body. A, B: Hematoxylin and Eosin staining. C: Insulin staining (note the focal positivity). D: Synaptophysin staining.