Insulinoma

Case Discussion

Case of a pancreatic neuroendocrine tumor with the clinical picture and CT features already supportive of insulinoma. Nuclear medicine PET/CT scans were performed for further functional imaging staging, note that the lesion is dotatate negative, which prompted a further GLP-1R study. 

Macroscopy: Labeled "Central pancreas". A segment of pancreas 43 x 23 mm, 33 mm in length, stapled at one edge (trimmed and underlying tissue inked green, opposite margin inked black. The ascending surfaces between the 2 longitudinal margins are covered by a smooth serosa (inked blue). The specimen is serially sliced longitudinally and shows a poorly defined, unencapsulated firm pale tan mass 20 x 19 x 18 mm. It is present 4 mm from the trimmed stapled margin and 7 mm from the opposite longitudinal margin. Within the attached fat, adjacent to the tumor is a pale yellow chalky nodule 4 x 4 x 3 mm.
Also received within the specimen container piece of fatty tissue 17 x 13 x 2 mm (inked green and trisected).

Microscopy:  Sections show pancreatic tissue containing a rounded, well-circumscribed cellular tumor. The tumor is composed of solid nests and interconnecting trabeculae of cells accompanied by a sclerotic stromal reaction. The tumor cells comprise a uniform population with round to ovoid nuclei, stippled chromatin with inconspicuous nucleoli, and a moderate amount of eosinophilic cytoplasm. Mitotic figures are rare (1 per 10 HPF). No amyloid is identified. Tumor is clear of the resection margins. No lymphovascular or perineural invasion is seen. The surrounding pancreatic tissue shows a focus of fat necrosis.
Immunoperoxidase stains have been performed and the tumor cells show strong positive immunostaining for insulin and synaptophysin. There is no staining for gastrin, ACTH, glucagon or somatostatin.
Ki-67 shows a proliferative index of 2%.

Conclusion: Central pancreas, excision: Pancreatic neuroendocrine tumor (insulinoma), grade 2, 20 mm in size, clear of margins. pT2.