Spindle cell pancreatic endocrine tumor associated with Cushing's syndrome

A 59-yr old female presented with Cushing's syndrome due to ectopic ACTH production. At the time of initial diagnosis an obvious source for the Cushing's syndrome was not found and the patient was treated with bilateral adrenalectomy. Three years later she presented with hyperpigmentation and evidence of ACTH overproduction. This time a CT scan localized a mass to the tail of the pancreas and a distal pancreatectomy was performed. The mass was composed of compact plump spindle cells arranged in interlacing fascicles, was well circumscribed, and did not display angioinvasion. Although isolated punctate foci of necrosis were noted, the overall mitotic count was 1 per 10 high power fields. Immunohistochemistry showed the tumor to be positive for chromogranin, synaptophysin, and ACTH. This case highlights an unusual histological variant of pancreatic endocrine tumor (PET), namely, one composed almost exclusively of interlacing spindle-shaped cells. This raises a wide differential diagnosis and the use of immunohistochemistry is required to arrive at the correct diagnosis. ACTH-producing PET are usually aggressive lesions with metastases at the time of presentation and aggressive biological behavior. However, this case was characterized by an indolent clinical course.