Ancient hematoma: a unifying concept for a post-traumatic lesion mimicking an aggressive soft tissue neoplasm.

We describe the clinicopathologic features of four cases of ancient hematoma occurring in the tensor fascia lata and perifascial tissue that clinically and radiologically mimicked aggressive soft tissue neoplasms. The lesions arose in three men and one woman, aged between 31 and 61 years. In three cases, an injury to the affected site had been noted 18 months, 19 years, and 20 years beforehand, respectively. At presentation, these deep-seated and enlarging lesions were highly suggestive of soft tissue sarcomas. Three lesions were treated by excision of an intramuscular or perifascial mass; in one case, repeated incomplete excisions were performed. Grossly, in three cases a well-circumscribed, fusiform mass with a soft cystic center and a fibrous pseudocapsule was described. Histologically, blood clot, fibrin, and predominant amorphous debris were seen in the central cavities; in three cases, the fibrous pseudocapsule contained clumped, eosinophilic, amorphous debris surrounded by a prominent xanthogranulomatous inflammatory infiltrate with numerous, multinucleated, foreign body-type, giant cells. Additionally, cholesterol clefts, areas of hemorrhage and dystrophic calcification, hemosiderin deposits, and cellular scar tissue were seen. Follow-up information revealed no evidence of recurrence or secondary infection in the three cases treated by local or wide excision; in the case in which incomplete excision was performed, continuous symptomatic growth was noted. Pathologic features of ancient hematomas are similar, if not identical, to those hematomas described previously as calcific myonecrosis, chronic expanding hematoma or posttraumatic cyst of soft tissues; we propose instead the term ancient hematoma. The reason for the commonly very long delay between the initiating trauma and presentation is uncertain.