Concomitant neuroendocrine tumor and gastrointestinal stromal tumor in a duodenal fine needle aspiration: A cytologic clue for neurofibromatosis type 1.

The identification of two cell populations displaying different cytologic characteristics in the same fine needle aspiration (FNA), one with an epithelioid appearance and the other spindle cell morphology, is an extremely rare phenomenon and potentially represents a source of diagnostic confusion. Depending on the lineage and relationship of the two cell types, the differential diagnosis is broad and encompasses a wide spectrum of entities. The current case describes the presence of nests and clusters of neuroendocrine cells associated with rare spindle cell fragments of gastrointestinal stromal tumor (GIST) in the same fine needle aspiration of a duodenal mass. Our literature analysis revealed that such combined cytologic findings were hitherto never reported and the concurrence of well-differentiated neuroendocrine tumor (NET) and GIST is almost pathognomonic for neurofibromatosis type 1 (NF-1).