A Rare Case of a Giant Intramuscular Lipoma of the Upper Extremity in a Pediatric Patient.

Although lipomas are the most common benign soft tissue tumors, the non-infiltrating intramuscular subtype is relatively uncommon. As these masses typically present between the ages of 40 and 70, few cases have been reported in the pediatric population. We present a case of a giant intramuscular lipoma of the biceps brachii in an adolescent. He presented with a slow-growing, tender mass and had no neurovascular compromise of the limb. MRI was utilized to visualize the mass, and a muscle-sparing excisional biopsy was performed. Histologic evaluation confirmed a diagnosis of a benign lipoma. The patient went on to heal without a functional deficit. Large, growing soft tissue masses warrant work-up to rule out malignancy. Advanced imaging and excisional biopsy are necessary to confirm the diagnosis of a benign giant intramuscular lipoma, which is especially rare within the pediatric population. We discuss the prevalence and treatment of intramuscular lipomas, including a literature review of reports in the pediatric population.