Fibrolipomatous Hamartoma of the Nerve Arising in the Neck: A Case Report With Review of the Literature and Differential Diagnosis.

We report an unusual case of a fibrolipomatous hamartoma that arose in a nuchal nerve. Typically, fibrolipomatous hamartoma, otherwise known as a neural fibrolipoma or lipomatosis of nerve, arises in the median nerve, brachial plexus, cranial nerves, or plantar nerves. The differential diagnosis is broad and includes benign and malignant spindle cell lesions, such as spindle cell lipoma, perineurioma, and myxoid liposarcoma. We were able to identify the lesion based on the typical histology, including triphasic composition with spindle cell, neural, and adipocytic components and whorled architecture. Because of the atypical location in the neck, detailed immunohistochemical staining was performed. The lesional spindle cells were negative for SMA, CD10, CD68, EMA, S100, PGP9.5, CD34, CD56, and beta-catenin. Colloidal iron stain highlighted marked intralesional mucin deposition. This detailed immunohistochemical profile is a useful diagnostic aid and to our knowledge has not been previously described.