Retroperitoneal malignant solitary fibrous tumor with two recurrences and lymphatic metastases：a case report

Malignant solitary fibrous tumor in the retroperitoneum is rare. We report a 67-year-old male with retroperitoneal malignant solitary fibrous tumor for more than 10 years, which recurred the second time accompanied by lymphatic invasion and lymph node metastasis. Computed tomography scanned multiple retroperitoneal masses and the tumor was widely implanted in the abdominal cavity. Histopathological examination showed that the tumor was mainly composed of short spindle cells, lining up sparse and dense areas. Mitotic figures were noted generally 6–8 per 10 high power fields (HPF) with local necrosis. The tumor invaded the circumferential liver, intestines, lymphatic vessels and lymph nodes. Combined with the immunohistochemical results, it was diagnosed as malignant solitary fibrous tumor, growing up again just two months after the latest surgery. Retroperitoneal malignant solitary fibrous tumors with repeated relapses, infiltrative growth and lymphatic metastasis suggest the need for careful and long follow-up.