Primary retroperitoneal solitary fibrous tumor: A case report.

Primary retroperitoneal masses have numerous differential diagnoses, many of which are rare entities. These can be neoplastic or nonneoplastic. Among the rare conditions are solitary fibrous tumors, which can either be benign or malignant. It is a mesenchymal, spindle-cell tumor, reported first in 1931 as a pleural tumor by Klemperer et al. A 20-year-old lady, with abdominal pain for 6 months, was diagnosed with a retroperitoneal mass on the left lower abdomen on USG which was confirmed by an MRI scan of the abdomen. The patient underwent laparoscopy-assisted excision of the mass. The final histopathological reports and immunohistochemistry reports revealed a solitary fibrous tumor. Solitary fibrous tumors (SFTs) are rare tumors in the retroperitoneum. In our search, fewer than a hundred cases have been reported. It has a characteristic "patternless pattern" in a microscopic study. Adverse outcomes of SFTs are associated with atypical features in histology, such as nuclear pleomorphism, necrosis, increased cellularity, and mitoses >4/10 HPF and size more than 10 cm. The standard of care is surgical excision with clear margins. Open surgeries have been done traditionally; we present a case where we performed the excision laparoscopically.