Endoscopic Ultrasound-Guided Fine-Needle Aspiration Cytology Diagnosis of Solid-Pseudopapillary Tumor of the Pancreas : A Rare Neoplasm of Elusive Origin but Characteristic Cytomorphologic Features

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Abstract
Clinical histories, endoscopic ultrasound (EUS)-guided fine-needle aspiration (FNA) material, and immunohistochemical stains performed on cell block samples of 6 solid-pseudopapillary tumors of the pancreas (SPTPs) were reviewed in the cases of 5 females (13–58 years) and 1 man (57 years); all had abdominal pain. Preliminary cytologic diagnoses at endoscopy included 1 SPTP, 2 low-grade neoplasms, and 3 pancreatic endocrine tumors. Variable numbers of branching fragments with central capillaries and myxoid stroma were seen in the smears of 5 of 6 cases but were more apparent in the cell block material of all cases. The cells had bland nuclear features and rare grooves. Extensive necrosis was noted in 1 case and rare mitotic figures in 1. SPTPs showed strong cellular immunoreactivity for vimentin and focal weak keratin reactivity. Neuron-specific enolase, α1-antitrypsin, and α1-antichymotrypsin stains performed in 2 cases were strongly positive. Subsequent surgical resection confirmed all diagnoses.