A rare case of primary hepatic solitary fibrous tumor associated with pregnancy

Purpose: To describe a case of histologically and immunohistochemically confirmed primary hepatic solitary fibrous tumor (SFT) associated with pregnancy. Case Report: A 40-year-old Caucasian woman G3P1021 with history of oral contraceptive use and no other known significant past medical history delivered via C-section in November of 2012. Two months post delivery, she noted that her abdomen did not decrease in size and sought medical attention. As part of the work-up, an abdominal MRI revealed a 15.9 cm mass centered in segment 4b of the liver with extension into segments 5 and 8 within the right lobe. In addition, an exophytic component extending inferiorly from the liver into the right mid abdomen was noted. The patient underwent an uncomplicated hepatic segmentectomy with cholecystectomy. Grossly, the tumor consisted of a firm tan-white well-circumscribed and partially encapsulated mass. Histologically, the tumor was composed of cytologically bland spindle cells with a patternless architecture with hypocellular and hypercellular areas embedded within a collagenous fibrous stroma with occasional dilated branching thin-walled blood vessels. The tumor showed no infiltrative margins or necrosis and a mitotic count of 1/10HPF. Tumor cells were strongly and diffusely positive for CD34, BCL-2, and vimentin; weakly positive for STAT6 (nuclear distribution); and focally positive for CD99 and β-Catenin. In addition, estrogen and progesterone receptors (ER and PR) were also performed and showed positive staining. The diagnosis of SFT was confirmed. To date, 36 months post-resection, our patient has been followed with imaging, showing no evidence of residual or recurrent disease. Conclusions: Primary hepatic SFT is exceedingly rare and even more so in association with pregnancy. Positive immunohistochemical staining of tumor cells for progesterone and estrogen receptors may indicate hormonal stimulation as a driver of neoplastic cell proliferation.