Well-Differentiated Liposarcoma of the Posterior Neck: A Case Report.

Soft tissue sarcoma is a rare differential diagnosis for masses arising in the head and neck regions and should be evaluated carefully. We report a case of a patient with a large posterior neck mass. Initially, the mass was suspected to be an intermuscular lipoma based on computed tomography (CT) scan and magnetic resonance imaging (MRI) findings, which showed a large, well-defined, lobulated intermuscular fatty mass. The mass was excised through a cervical incision while preserving the surrounding vital muscular and neurovascular structures. Histopathological examination revealed a well-differentiated liposarcoma (WDLS) with adipocytes of various sizes, scattered nuclear atypia, and expanded fibrous septa containing atypical stromal spindle cells positive for MDM2 staining. These findings confirmed the mass as a WDLS. We describe our approach to the diagnosis and treatment of this condition in detail.