Diagnosing clear cell neuroendocrine tumors on cytological specimens: Report of two cases and brief literature review.

Although many of the common manifestations of Von Hippel-Lindau (VHL) disease are relatively well known, there is one particular entity which is quite rare, but which appears to show a specific predilection for VHL patients. This entity is clear cell neuroendocrine tumor (NET). It is a difficult diagnosis to make due to its cytomorphologic similarities to other entities, such as metastatic clear cell renal cell carcinoma and paraganglioma, amongst others. These tumors, however, are characteristically positive for neuroendocrine markers such as synaptophysin and chromogranin, as well as cytokeratins. Emerging evidence also suggests that clear cell NETs in VHL patients are specifically positive for inhibin, when compared to their counterparts in non-VHL patients, which may assist in the diagnosis in as yet undiagnosed patients with VHL disease. Herein, we present two cases of inhibin-positive clear cell NETs, one in a VHL patient, and the other in a non-VHL patient. These cases propose a potential warning to those relying on inhibin positivity to incite an expedition down a rabbit hole for a diagnosis of VHL. Diagn. Cytopathol. 2017;45:757-760. © 2017 Wiley Periodicals, Inc.