Underestimation of a Giant Lipoma on Magnetic Resonance Imaging: A Rare Case Report

Introduction: Lipomas are the most common benign mesenchymal tumor. The solitary subcutaneous lipoma accounts for approximately one-quarter to one-half of all soft-tissue tumors. Giant lipomas involving the upper extremities are rare tumors. This case report presents a subcutaneous giant lipoma in the upper arm weighing 350 g. Due to its long-term presence, the lipoma caused discomfort and pressure effects in the arm. Gross underestimation on magnetic resonance imaging (MRI) made its removal challenging and difficult. Case Report: Through this case, we report a 64-year-old female who consulted us in the clinic with complaints of discomfort, feeling of heaviness, and a mass in the right arm since 5 years. On clinical examination, there was asymmetry in her arms with her right upper arm showing a visible swelling (8 cm × 6 cm) over its posterolateral aspect. On palpation, the mass was soft, boggy, not attached to the underlying bone or muscle, and not involving the skin. A provisional diagnosis of lipoma was made and the patient was asked to undergo plain and contrast-enhanced MRI for the confirmation of the diagnosis, the extent of the lesion, and infiltration into the surrounding soft tissue. The MRI revealed a lobulated deep lipoma in the subcutaneous plane with pressure effects over the posterior fibers of the deltoid muscle. Surgical excision of the lipoma was carried out. The cavity was closed using retention stitches to prevent the formation of a seroma or ematoma. Complaints of pain, weakness, heaviness, and discomfort completely subsided by the 1st month follow-up. The patient was then followed up every 3 months for 1 year. No complication or recurrence was noted throughout this period of time. Conclusion: The extent of lipomas can be underestimated on radiological imaging. It is common to find a bigger lesion than reported and to plan and execute the incision and surgical approach accordingly. Blunt dissection should be preferred when there are chances of neurovascular involvement or injury. Keywords: Giant lipoma, benign, upper arm, surgical excision, debridement.