Giant cystic superficial low-grade fibromyxoid sarcoma

Low-grade fibromyxoid sarcoma (LGFMS) is a rare type of fibrosarcoma characterized by combination of myxoid and fibrous zones consisted of bland spindled cells. Despite its innocuous histopathologic appearance, LGFMS can produce local recurrence and distant metastasis in the significant number of cases. Tumors are usually situated in deep soft tissues, whereas superficial localization in the dermis and subcutaneous fat is rare. We present a case of 56-year-old man with the huge tumor on the lateral part of the right buttock that had been slowly enlarging over the previous 15 years. Needle aspiration cytology provided only serohemorrhagic fluid with the red blood cells and rare inflammatory elements. Complete surgical excision revealed subcutaneous tumor, measuring 220 × 180 × 130 mm, which was completely cystic, with the residual tumor tissue in the 3- to 25-mm-thick wall. Histopathologic, immunohistochemical, and cytogenetic analysis confirmed LGFMS diagnosis. Long evolution, large size, and the superficial location could cause the repetitive tissue damage and hemorrhage, eventually transforming the tumor into a large cystic mass. In some parts, collagen rosettes composed of eosinophilic core surrounded by a palisade of tumor cells could be seen, occasionally appearing to sprout from the perivascular fibrous coat. Data from the literature regarding cystic appearance as well as the superficial location and the size of LGFMS in relation to the clinical outcome are presented and discussed.