1003 - Symptomatic Myxomatous Neurofibroma inducing compression of External Rotators and Coccyx Canal

A 72 year old male with a past medical history of irritable bowel syndrome and Hailey Hailey disease presented with an insidious onset of right gluteal pain and right hamstring pain that worsened with sitting. Physical findings included right sided flank pain with ipsilateral rotation, pain reproducibility with deep piriformis palpation, and neurological examination within normal limits. Plain films were unremarkable. After failure to respond to an ultrasound-guided piriformis trigger point injection, an MRI of the pelvis without contrast was obtained, revealing an indeterminate soft tissue pelvic mass. A contrast MRI study showed heterogenous enhancement of a multilobulated mass in the right lower pelvis adjacent to the obturator externus and internus muscles in the region of the coccyx canal. CT guided biopsy of the mass revealed S100 immunostain consistent with a neurofibroma. CT guided injection of the right pelvic nerve sheath tumor with local anesthesia and steroid resolved the pain. 

Discussions:

This case illustrates the difficulty to manage a patient with typical pain patterns not stemming from classical pain generators. Injection of analgesic into the right obturator internus nerve sheath under CT guidance, provided significant relief and improved quality of life. The patient is actively being monitored for recurrence of pain or possible surgical intervention. 


Conclusions:

Myxomatous Neurofibroma masses are not generally in the differential for associated pain in the gluteal region, yet this case highlights the importance and need of flexibility when it comes to assessing patients. Anchoring on to most common diagnosis and ignoring the pertinent negatives of findings could lead to complications and diminished quality of life for patients in unexplainable pain.