Large Deep Temporal Lipomatous Mass Mimicking Liposarcoma on MRI: A Brief Clinical Report.

Intramuscular lipoma of the temporalis muscle is rare and may be difficult to distinguish from malignant lipomatous tumors when MRI shows atypical features. A 76-year-old woman presented with a progressively enlarging right temporal mass and a history of prior subcutaneous lipoma excision at the same site. Contrast-enhanced MRI revealed a large deep lipomatous mass with a heterogeneous nonadipose component involving the anterior temporalis muscle, raising concern for atypical lipomatous tumor/well-differentiated liposarcoma (ALT/WDL). The lesion was excised through a preauricular-based incision with temporal extension. Intraoperative frozen section suggested a benign lipomatous lesion, and final pathology confirmed intramuscular lipoma without lipoblasts or nuclear atypia. MDM2 immunostaining was negative, whereas CDK4 showed only focal nuclear staining. At 6 months, facial nerve function was preserved, and no clinical recurrence was evident. This case highlights that a large deep temporal intramuscular lipoma may mimic liposarcoma on MRI and that safe management requires integrated radiologic, intraoperative, and histopathologic correlation.