Working Diagnosis:
Volar wrist mass, probable Fibrolipomatous Hamartoma.
Rare condition involving diffuse infiltration of peripheral nerves by normal-appearing fibrous connective tissue.
Causes: congenital malformation, abnormal development of flexor retinaculum, trauma, chronic nerve irritation.

Treatment:
Understanding the potential risk of alternative malignant diagnosis, characteristic progression, and/or parasthesia, the patient ultimately elected for expectant management. He had no neuropathy and believed that the palpable click was of minimal concern in comparison to the aforementioned risk.

Outcome:
Patient returned to full work participation with a wrist splint for comfort. At his one month follow-up, he had persistent clicking but improved pain and no neuropathy. He was advised to return if worsening pain or new onset of growth leading to neuropathy, which could potentially be treated symptomatically with a carpal tunnel release without tumor removal.

Author's Comments:
Due to the rarity of this condition (180 published cases since 1953), there are no clear guidelines for diagnosis and treatment.
MRI appearance is unique, showing serpentine nerve bundles embedded within abundant hyperintense adipose material with fine fibrous septa coursing along the median nerve.
Tissue biopsy can be helpful in supporting the diagnosis, as its fibrofatty infiltration around the nerve fascicles distinguishes it pathologically from other intramural tumors. Biopsy is often done in conjunction with complete excision in order to eliminate the risk of malignancy, as well as to provide any symptomatic relief from pain or compression to the median nerve. However, this procedure confers significant risk of median nerve damage and potentially devastating functional sequelae or neuroma formation.

Editor's Comments:
Whereas the median nerve is the most common location that these lesions occur, they can also occur within the ulnar nerve as well. Histologic features are usually the same for all fibrolipomatous hamartomas but the gross morphological features can vary widely from simple and small lesions to more complex and extensive lesions involving several or all of the upper extremity nerves. Knowing the characteristic radiologic findings can help guide treatment options and potential for biopsies if extensive peripheral nerve involvement is seen.

References:
Tahiri Y, Xu L, Kanevsky J, Luc M. Hamartoma of the median nerve: a comprehensive review and systematic approach to evaluation, diagnosis, and treatment. J Hand Surg 2013; 38A:2055-2067.
Razzaghi A, Anatakis D. Lipofibromatous hamartoma: review of early diagnosis and treatment. Can J Surg, Vol. 48, No. 5, Oct 2005.

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