Intramuscular Hemangioma of the Triceps Brachii Muscle: A Case Report.

Introduction: Intramuscular hemangioma (IMH) is a rare type of benign tumor that represents less than 1% of all hemangiomas. Chronic pain and a palpable mass are the most common symptoms. Due to the atypical clinical characteristics of the disease, accurate diagnosis is difficult. Misdiagnosis of IMH as malignancy can occur due to similarities in imaging features between IMH and malignancy. To diagnose IMH accurately, multiple imaging modalities, including X-ray, MRI, CT, and ¹⁸F-FDG PET/CT, can be used. However, the final diagnosis of IMH is confirmed through histopathological examination.

Case: This case reports a 16-year-old girl diagnosed with IMH in the triceps brachii muscle. Seek medical attention due to pain and discomfort in the left shoulder. Initial imaging with contrast-enhanced MRI and CT suggested synovial sarcomata. The moderate uptake of FDG on positron emission tomography/computed tomography (PET/CT) also raised suspicions of malignancy. The pathological findings revealed an intramuscular hemangioma with thrombosis and thrombus organization.

Conclusion: The accurate diagnosis of IMH can be challenging due to the absence of distinct clinical symptoms and imaging findings. When evaluating periarticular intramuscular lesions, IMH should be considered if the MRI shows mixed signals with heterogeneous enhancement. Despite the moderate uptake of FDG seen in some IMH cases, it should not automatically rule out the possibility of IMH. Hence, a combination of imaging modalities and histopathological examination is crucial in ensuring a correct diagnosis of IMH.