Utility of cytomorphology in distinguishing solid pseudopapillary neoplasm of pancreas from pancreatic neuroendocrine tumor with emphasis on nuclear folds and nuclear grooves.

BACKGROUND: Pancreatic solid pseudopapillary tumor (SPN) and pancreatic neuroendocrine tumors (Pan-NET) have close resemblance on imaging and cytomorphology, though they differ in their prognosis and treatment strategy. SPNs are low-grade indolent tumors while Pan-NETs harbor malignant potential with propensity to metastasize. We aim to differentiate SPN from Pan-NET based on cyto-morphology; to classify nuclear membrane (NM) irregularities or nuclear folds into four grades and see whether they bear any difference with respect to the two entities.

METHODS: Eighteen and ten confirmed cases of SPN and Pan-NET were included in the study. Smears were assessed for architecture, background changes, cellular, and nuclear features, which were compared between the two study groups. Nuclear folds were classified into four grades. Nuclear folds and nuclear grooves were also compared between the two groups.

RESULTS: All SPN patients were females; mean age of 28 years. Pan-NET patients had equal male to female ratio; mean age of 46 years. Both SPN (78%) and Pan-NET (71%) showed predilection for pancreatic head. Mean size of lesion was 4.8 cm and 3.1 cm in SPN and Pan-NET groups. Papillary pattern, branching capillaries, degenerative background were significantly more prominent in SPN; sudden anisonucleosis and cytoplasmic granularity in Pan-NET. Metachromatic matrix, hyaline globules, and nuclear grooves were noted exclusively in SPNs. Nuclear fold grades 2 and 3 were more characteristic of SPN than Pan-NET (P = 0.041 and 0.002, respectively).

CONCLUSIONS: Cytomorphology is vital in differentiating SPN from Pan-NET with nuclear folds being an important nuclear feature.