Discussion
The presence of a hematoma in the extremities is usually a straightforward diagnosis. However, the unusual circumstances of this case highlight all the indications for investigation for possible soft-tissue sarcoma when a patient presents with what appears to be a benign condition.
Hematomas are rare in the absence of trauma or coagulopathy, with chronic expansion of hematomas rarer still.4,7,10-11 The patient had no evidence of coagulopathy because of her ability to have an uncomplicated pregnancy and elective cesarean section. She denied a history of trauma, and the location of her hematoma at the posterior distal thigh is an uncommon site of injury. In this setting, fine-needle aspiration and serial imaging to assess for progressive increase in lesion size were indicated to rule out malignancy.2
MRI is the gold-standard imaging modality for distinguishing soft-tissue masses from hematomas.5,12-14 Unlike the typical appearance of a hematoma, sarcomas of the soft-tissue extremities are often complex cystic lesions with multiple septations, internal soft-tissue components, and relatively ill-defined margins.15-17 However, as a hematoma becomes chronic, it can develop a fibrinous capsule, and the contents can manifest an atypical, heterogeneous appearance from scattered, progressive accumulation of blood products that is essentially indistinguishable from sarcomas on imaging.5
Because of the expansion of the hematoma and the atypical appearance of the mass on imaging, repeated core biopsy and, eventually, open biopsy were indicated, despite a preliminary negative diagnosis based on fine-needle aspiration. This resulted from the possibility of sampling error that is particularly relevant to cystic sarcomas, because only portions of the mass may be composed of malignant cells.2 An unusual aspect of this case is the regional lymphadenopathy noted on MRI, because regional lymphatic spread is a known mechanism of metastasis in soft-tissue sarcomas.18 However, the inguinal biopsies showed a chronic inflammatory infiltrate and were negative for malignancy, and enlarged nodes were not seen on imaging several months later. It is possible that the lymphadenopathy resulted from an unrelated process; alternatively, it may have been secondary to impaired lymphatic drainage because of mass effect from the hematoma, which also caused temporary lower extremity swelling.
The distal posterior thigh is an unreported location for a chronic expanding hematoma. Our patient developed slowly progressive lower-limb swelling and, eventually, paresthesias because of displacement of the neurovasculature, an unusual sequela that was recently reported in a similar case of an acute spontaneous hematoma in a patient on warfarin.19 Rupture of a Baker cyst is a possible inciting factor in our patient, although the proximal location of the lesion and the clearly defined tissue plane on MRI between the hematoma and the popliteal region make this unlikely. Finally, the patient’s lesion showed no evidence of vascular flow on Doppler ultrasonography, although giant hematomas secondary to popliteal aneurysm rupture have been reported.20-22
Conclusion
This case highlights the features of a chronic expanding hematoma that can suggest soft-tissue sarcoma and shows the recommended diagnostic steps to differentiate the 2 conditions. This case also describes an unreported location for a chronic expanding hematoma with resulting progressive neurovascular displacement caused by mass effect. We recommend careful monitoring of patients with similarly expansile lesions in this region for signs of neurovascular compromise.