Microcystic/reticular schwannoma of the pancreas: A potential diagnostic pitfall

Abstract

Schwannomas occurring in the pancreatic head are rare benign non-recurring mesenchymal neoplasms and are reported to show classic morphologic features. Herein we report a case of a 62 year old male presenting with a 5 cm mass in the pancreatic head encasing the portal vein and the truncus coeliacus. Preoperative fine needle aspiration revealed malignant tumour cells consistent with a moderately differentiated adenocarcinoma. A Whipple surgery was performed after palliative chemotherapy. Histological evaluation revealed a multinodular unencapsulated tumour with focal infiltration into pancreas parenchyma and a striking microcystic/reticular growth pattern. Anastomosing and intersecting strands of spindle cells with eosinophilic cytoplasm set in a myxoid partly collagenous stroma were observed. The tumour cell nuclei were round oval and tapered and showed inconspicuous small nucleoli. Degenerative nuclear atypia was seen. Mitotic activity was sparse (1/50 HPF). Pleomorphism or necrosis was absent. The tumour cells showed strong nuclear and cytoplasmic positivity for S-100 protein, and focal positivity for glial fibrillary acidic protein. The diagnosis of a microcystic/reticular schwannoma was made. The awareness of and, to some extent, the knowledge about this rare tumour are needed to achieve the correct diagnosis and to avoid confusion, especially with malignant pancreatic neoplasms.

Cutaneous microcystic/reticular schwannoma: a poorly recognized entity

“…Microcystic/reticular schwannoma was originally reported by Liegl et al as a distinctive variant of schwannoma showing predilections for the gastrointestinal tract . Nevertheless, similar lesions have infrequently been also reported in the respiratory tract, adrenal gland, deep soft tissue of the face and upper back, cervical spine, parotid gland, pancreas, mesentery and skin . Prior to the present study, only three microcystic/reticular schwannomas occurring in the skin have been described .…”

Microcystic/Reticular Schwannoma of the Proximal Sigmoid Colon: Case Report With Review of Literature

“…7 Microcystic/reticular schwannomas can be a problematic differential diagnosis even in cases of nonluminal gastrointestinal tract tumors like pancreas. This was highlighted by Liegl et al 15 in their recent case report of a 5-cm mass in the pancreatic head. The fine-needle aspiration was interpreted as malignant tumor cells consistent with a moderately differentiated adenocarcinoma, whereas the histology of the excised mass was consistent with a microcystic/reticular schwannoma.…”

MR imaging features of pancreatic schwannoma: a Chinese case series and a systematic review of 25 cases

“…Characteristic enhancement patterns of pancreatic schwannomas are mild heterogeneous/homogeneous enhancement at arterial phase and thereafter progressive enhancement at the portal and delayed phases, which are likely as a result of variable degree of pancreatic tumor cellularity or degenerative changes like cystic degeneration, calcification, hemorrhage, and necrosis [10,[36][37][38]. Although MRI findings of pancreatic schwannoma are usually similar to those of other abdominal sites (i.e.…”

“…Immunohistochemical labeling is usually needed to make the accurate diagnosis. Strong positive staining for S-100 on immunohistochemical examination is a major marker to make the final diagnosis of pancreatic schwannoma [3,[10][11][12]. Benign types accounts for 65% of all neurogenic neoplasms, but, up to 15% are malignant transformation.…”