cd 99 immunocytochemistry in solid pseudopapillary tumor of pancreas: a study on fine-needle aspiration cytology smears

Background: Solid pseudopapillary tumor of pancreas (SPTP) is a rare pancreatic tumor of uncertain histogenesis usually affecting young women. Though these tumors have characteristic cytomorphology, it is sometimes difficult to differentiate them from neuroendocrine tumors of the pancreas. We reviewed cases of SPTP to delineate the diagnostic cytological features and also observed utility of CD 99 (MIC 2) immunostaining to aid in the diagnosis of this tumor. Aims: This study was designed to demonstrate the utility of CD 99 immunostaining along with cytological features for making a pre-operative diagnosis and delineating it from the neuroendocrine tumor of pancreas which is a close mimic. Materials and Methods: Cytomorphological features of 11 cases of solid pseudopapillary neoplasm diagnosed by pre-operative fine-needle aspiration cytology (FNAC) at our institute were reviewed. Immunocytochemistry for CD 99 was also performed on the smears. Results: All the cases had cellular smears with monomorphic cells lying singly, as loosely cohesive clusters as well as forming delicate pseudopapillae. Presence of intra and extra-cellular basement membrane material, background foamy macrophages and nuclear grooves were the other salient features. Immunocytochemistry for CD 99 could be performed on eight cases and demonstrated typical paranuclear dot-like positivity. Conclusions: Pre-operative early diagnosis of SPTP can be made by FNAC which can further be aided by CD 99 immunocytochemistry.