A 38-year-old male was admitted to our hospital complaining of a huge mass on his thigh. CT scan and MRI revealed an enlarging intramuscular tumor in his quadratus femolis muscle suggestive of malignancy. The exact diagnosis was not available with open biopsy. As we coould not rule out the suspicion of malignant tumor, resection was performed, consisting as a partial (2/3) resection and curettage of most contents. Histological examination of the resected mass showed an organized hematoma

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... ded by dense fibrotic tissue, eosinophilic material, capillary vessels and many inflammatory cells especially histiocyte. The mass was diagnosed as chronic expanding hematoma as a result. The mechanism of chronic expanding hematoma is unclear. In our review of literature, only 10 cases including this one located in the extremities could be found. About two years later, the mass has reduced and the patient activity of ADL improved significantly.