Intraneural lipoma of the ulnar nerve: A rare case report and review.

Intraneural lipoma of the ulnar nerve is a rare peripheral nerve tumor in an uncommon location. Although its benign course, it can cause disabling symptoms such as pain, diminished sensation or paraesthesia, tenderness, and occasionally even loss of strength. We present the case of a middle age woman with insidious paresthesias and swelling of the hypothenar eminence of the left hand for over 1 year. A hand and wrist radiograph first confirmed a focal soft tissue mass with fat density and excluded potential bone lesions. Then, an ultrasound was performed that showed a slightly hyperechoic mass with a fibrillated pattern in contiguity with the proximal aspect of the ulnar nerve. The morphological arrangement of this mass, its location along ulnar nerve distribution and the main signal characteristics in magnetic resonance imaging such as hyperintensity in T1- and T2-weighted images and hypointensity in fat saturation sequences inferred an intraneural lipoma. Due to the progressive symptoms, elective resection of the lesion was performed with full recovery of the symptoms.