Benign nerve sheath tumors on urinary bladder biopsy.

Benign nerve sheath tumors (schwannoma and neurofibroma) involving the urinary bladders are rare with only case reports and limited series. We identified 6 neurofibromas and 2 schwannomas involving the urinary bladder. Of the 8 cases, 7 were sent to one of the authors in consultation and the last came for treatment to The Johns Hopkins Hospital. Patients (3 males, 5 females) ranged in age from 3 to 69 years old (average 36 y old). Presenting symptoms included recurrent infection in 6 patients, hematuria in 3 patients, and irritative symptoms in 3 patients (some patients with 2 symptoms). Three patients had a pelvic mass on physical examination. Three patients (3/8) had a solitary lesion in the bladder, 4 patients (4/8) had multifocal lesions, and 1 patient had no information available. Five patients underwent local resection. One patient, who was 3 years old, had multiple plexiform neurofibromas within the bladder and did not have surgical treatment and another patient is also undergoing surveillance. One patient had no treatment information available. Seven patients had clinical follow-up information available. The length of follow-up varied from 2 to 124 months (average 47 mo). Three out of the seven patients with follow-up information had neurofibromas in other sites, including the skin, uterus, mesentery, and ureter. One patient was known to have other stigmata of neurofibromatosis. Both cases with schwannoma had only bladder involvement. No family history of neurofibromatosis and no genetic studies were performed on any of the patients. Three neurofibromas were of the diffuse type, with 2 cases plexiform, and 1 case could not be subtyped. Neither recurrence nor malignant transformation was demonstrated on follow-up. The importance of accurately diagnosing plexiform neurofibromas of the bladder is that a subset harbors neurofibromatosis. If the lesion is focal, conservative excision is the choice of treatment with a low risk of recurrence. Diffuse neurofibromas can be difficult to diagnose leading to delay of treatment and potentially the need for a more extensive excision. Once recognized as a neurofibroma, it is important to identify it as a diffuse neurofibroma, given its lack of relationship to neurofibromatosis.