The management of large intramuscular hematoma in the extremities is often challenging, especially when the etiology is ambiguous. Hematoma can be spontaneous or secondary to trauma, bleeding disorders, tumors [1, 2]. When a patient exhibits an enlarging traumatic hemorrhagic mass without any bleeding disorders or bruising, healthcare providers should consider various potential diagnoses. These include chronic expanding hematoma, aneurysm, abscess, and soft tissue sarcoma. Undetected sarcomas can lead to devastating outcomes [1, 2]. Such cases pose significant challenges, as the symptoms of injury and imaging results may obscure the presence of an underlying tumor.

A 45-year-old man was sent to our facility with a painful, swollen left thigh. The patient exhibited signs of toxicity, including high fever. His laboratory results showed an elevated white blood cell count of 23,000, an increased erythrocyte sedimentation rate, and abnormal coagulation parameters.
On examination, the swelling was found to be firm, tender, and diffuse over the anterolateral aspect of the thigh associated with foul-smelling discharge (Fig. 1).

Upon investigating the patient’s medical history, it was discovered that he had experienced a fall approximately 8 months prior. Although he was able to ambulate following the incident, he subsequently developed progressively increasing swelling and discomfort. Plain radiographs and laboratory tests yielded normal results. The patient’s medical record also indicated a previous cardiac angioplasty, for which he was prescribed anticoagulants. Magnetic resonance imaging (MRI) identified an organizing hematoma measuring 21 × 13 cm on the anterolateral aspect of the thigh (Fig. 2a, b, c). The hematoma was explored and drained elsewhere. No samples were submitted for histopathological examination or culturing. The patient returned after 2 weeks, exhibiting symptoms of fever, pain, and surgical site discharge. Blood tests revealed elevated white blood cell counts. Computed tomography angiography detected a 21 × 13 × 13 cm mass containing air pockets and peripheral neovascularity, suggesting a subacute compartment hematoma. Subsequent MRI findings described a heterogeneous mass with a central necrotic region (Fig. 3). A second debridement procedure was performed 15 days after the initial surgery. The culture report indicated the presence of Acinetobacter baumannii. Suitable antibiotics were administered, but the patient’s condition did not improve. The individual continued to experience high-grade fever, along with pain and discharge at the surgical site. Radiographs of the thigh showed air in soft tissues (Fig. 4). Suspecting gas gangrene, an orthopedic surgeon referred the case to our team for further evaluation and treatment. At our institute, surgical intervention was scheduled, including exploration, debridement, and biopsy, to reduce the infective focus and establish a provisional diagnosis of the soft tissue mass. The gas shadows were presumed to be due to the Gram-negative infection (Acinetobacter), along with a gaping wound, and not clostridial gas gangrene as was suspected by the primary surgeon. An orthopedic oncologist was consulted for their expertise in view of the heterogenous mass on MRI. A soft tissue tumor was suspected and intra-operative frozen section was planned.
During the operation, surgeons encountered a highly vascularized mass (Fig. 5). A sample was submitted for Frozen, which identified the tissue as a spindle cell tumor. Histopathology was suggestive of un-differentiated pleomorphic spindle cell sarcoma (Fig. 6). Subsequent positron emission tomography scan showed a metastatic lesion in the lung (Fig. 7). Deep tissue cultures grew Enterobacter cloacae. The patient was administered injection colistin 3MU and injection ciprofloxacin. The patient’s hemodynamic and hematological status improved after undergoing debridement and receiving antibiotic treatment. An orthopedic oncologist performed a subsequent wide total resection (Fig. 8a and b). Wound was partially closed and distal open aspect was covered with negative pressure wound therapy (Fig. 9).

Once granulation tissue began to form, a split-thickness skin graft was applied. The patient returned to our facility 7 months later with the wound fully healed (Fig. 10). At that time, the individual was undergoing chemotherapy for metastatic lesions, but there were no signs of infection at the surgical site.

The patient succumbed to the disease 12 months after initial presentation at our institution, with metastasis being the cause of death.

Mesenchymal-derived tumors known as soft-tissue sarcomas form a diverse group characterized by their invasive local growth patterns. These malignancies account for approximately 1% of cancerous tumors in adults ^[1]. Typically, it manifests as a painless mass and can develop anywhere on the body. Around 45% of soft tissue sarcomas emerge near the long bones of the extremities, with a preference for the lower limb. Sarcomas commonly spread to the lungs through the bloodstream. Dissemination through the lymphatic system is uncommon ^[2]. Soft tissue sarcoma can sometimes be mistaken for a deep intramuscular hematoma in its initial diagnosis. Healthcare providers should consider the possibility that a soft tissue sarcoma might be mimicking a hematoma following an injury. Due to its superior tissue contrast resolution, MRI serves as an effective diagnostic tool for evaluating soft tissue masses ^[3]. MRI continues to be the gold standard in distinguishing soft tissue tumors from hematomas. However, the literature presents conflicting information regarding the sensitivity of diagnosis and grading. MRI is unable to predict malignancy, as the characteristics typically associated with malignant lesions often overlap with those observed in benign tumors ^[4]. Furthermore, a significant percentage of malignant lesions may appear deceptively benign with the currently used criteria [5, 6]. MRI also performs poorly in the histological classification of soft tissue tumors ^[6]. MRI scans provide only indirect insights into tumor histology by displaying signal intensities associated with certain physicochemical properties of tumor components. As a result, these images primarily reflect the overall morphology of the lesion rather than its underlying histological characteristics. Furthermore, the differentiation process is complicated by time-dependent changes within tumors, which occur due to intra-tumoral necrosis and/or hemorrhage. Throughout various stages, the hematoma exhibited diverse signal intensities ^[7]. On T1-weighted imaging (T1WI), acute hematomas appear as high-intensity signals, while they exhibit low-intensity signals on T2-weighted imaging (T2WI). In contrast, chronic hematomas are typically encapsulated by fibrous tissue, which presents as low-intensity signals on both T1 and T2WI ^[8]. In sarcoma imaging, the solid component appears dark in T1-WI and bright in T2-WI. When contrast is administered, it results in a non-uniform enhancement pattern ^[9]. There are quite a few reports in the literature of high-grade sarcomas mimicking hematomas in the extremities. Ogose et al. ^[10] reported an extra-skeletal Ewing sarcoma resembling a traumatic hematoma in a 16-year-old boy with a history of recurrent hematoma in the thigh. Imaizumi et al., ^[7] reported six cases that were initially diagnosed with traumatic hematomas but later turned out to be soft tissue sarcomas. The cytology of percutaneous aspiration was unfavorable for malignancy in five of the six patients having rapidly growing lesions. The final diagnosis was only made after an open biopsy several weeks later. Engel et al., ^[11] reported on a young man who had a history of trauma to his thigh, initially diagnosed as an adductor compartment hematoma; however, it was histologically identified as a synovial sarcoma after surgery. In their study ^[7], Imaizumi et al. retrospectively reviewed the history and imaging studies and concluded that MRI was a reliable diagnostic tool for the differentiation between hematoma and sarcoma only if studied extensively. However, as presented in this report, the MRI images can be similar in both pathologies, and high-grade soft tissue sarcoma cases presenting after trauma could easily be misdiagnosed as hematomas related to that recent injury.

In cases of chronic intramuscular hematomas resulting from trauma, healthcare professionals should maintain a high level of clinical vigilance. While radiological findings are valuable, they should serve as a guide rather than the sole determinant in diagnosis. It is crucial to consider the possibility of a high-grade sarcoma in these patients. Any uncertainty should be addressed through image guided/surgical biopsies.

The interpretation of radiological results should be done in conjunction with the patient’s clinical context. Effective collaboration between disciplines and adherence to established protocols can facilitate the accurate diagnosis of most medical conditions.