Cellular Schwannoma Arising from Sigmoid Mesocolon Presenting as Torsion
A 58-year-old female presented to emergency department with acute abdomen of 2 h onset. Clinically, the patient was afebrile and had tenderness in lower abdomen. Ultrasonography (USG) and emergency plain computer tomography (CT) scan was carried out. USG revealed a homogenous and hypoechoic solid lesion in pelvis without any evidence of lymphadenopathy. Plain CT displayed a large pelvic mass of approximate size of 17 cm × 15 cm × 12 cm extending to lower abdomen, with mass effect causing displacement of the bowel superiorly and toward right. Mass appeared relatively dense in plain CT. Right ovary could not be visualized and left ovary appeared bulky. There was moderate degree of ascites and minimal pleural effusion. Based on clinical symptoms and plain CT findings, a presumptive diagnosis of torsion of right ovarian neoplasm was made. Emergency laparotomy was carried out. During laparotomy, it was evident that the large mass was arising from sigmoid mesocolon and was twisted around its axis with marked congestion on its surface. Complete surgical excision was carried out. Histopathological examination of the specimen was carried out. Cut surface [] of the specimen revealed well encapsulated lesion containing multiple nodules of grey white solid areas and areas of congestion. Microscopic examination [] of multiple sections from grey white solid areas revealed fascicles, whorls and palisades (Antoni A areas) of spindle cells varying from wavy nerve bundles to plump elongated cells with moderate eosinophilic cytoplasm. Verocay bodies were absent and Antoni B areas were scanty. Dense hyalinization was evident in all the sections studied. Small to large caliber hyalinized congested blood vessels were seen. Immunostaining showed diffuse S-100 positivity [, inset] and no reactivity for CD117, CD34, SMA, CD31, HMB-45, and desmin. A diagnosis of cellular schwannoma with torsion was conferred.