Deep-Seated Simplicity: Unmasking Intramuscular Lipomas

Intramuscular lipomas (IMLs) are rare benign soft tissue tumours that account for less than 1% of all lipomas and often present a diagnostic challenge due to their deep location and infiltrative growth pattern. We report a case of a 75-year-old male with a 15-year history of a painless, gradually growing swelling over the posterior aspect of the left shoulder. Clinical examination revealed a soft, mobile, non-tender swelling causing no functional limitation. Ultrasonography and magnetic resonance imaging confirmed an intramuscular lipoma involving the deltoid and triceps muscles. The patient underwent complete surgical excision, and histopathological analysis revealed mature adipocytes with no atypia, consistent with benign lipoma. The postoperative course was uneventful, with no signs of complications or recurrence. This case highlights the importance of considering IMLs in the differential diagnosis of deep soft tissue masses.