Diagnosis
Neurofibroma of the urinary bladder, characterized by Pseudomeissnerian bodies.
Diagnosis
Neurofibroma of the urinary bladder, characterized by Pseudomeissnerian bodies.
Discussion
Neurofibromas are typically found in the skin and, occasionally, in deep neural trunks. Occurrences in visceral organs such as the urinary bladder are exceedingly rare, with the first reported case in the bladder dating back to 1878 during an autopsy. To date, only about 70 cases have been documented in the English literature, most of them affecting young patients as a sequela of neurofibromatosis type 1 (NF1) caused by NF1 gene mutations. Fewer than 10 cases of primary neurofibromas of the urinary bladder unrelated to NF1 have been reported.
Neurofibromas are classified into three main subtypes: localized, diffuse, and plexiform. The localized type is the most common, accounting for the majority of sporadic cases and cutaneous neurofibromas. These tumors are usually nodular and well circumscribed. Plexiform neurofibromas, characterized by their classic “bag of worms” appearance, are strongly associated with NF1 and are considered pathognomonic for the disease. Diffuse neurofibromas, by contrast, are defined by their infiltrative growth with ill-defined borders that extend into deeper layers, often involving adnexal structures, fat, and muscle. A characteristic feature of diffuse neurofibromas is the frequent presence of pseudomeissnerian bodies. Although this subtype has been reported to have some association with NF1 in cutaneous cases, its relationship to NF1 in visceral organs, such as the urinary bladder, remains unclear.
Diagnosing diffuse neurofibromas of the bladder is challenging because the epidermal, dermal, and subcutaneous layers present in skin neurofibromas are absent. Involvement of the lamina propria and submucosa can produce a homogeneous, delicate eosinophilic matrix that may be mistaken for normal tissue. Moreover, limited access to deeper layer especially in transurethral resection specimen makes it difficult to distinguish true infiltration. In cases like ours, where pseudomeissnerian bodies dominate the histologic findings and S100 immunostaining highlights only rare spindle cells outside these structures, subtype classification becomes particularly challenging. Molecular testing for NF1 mutations is therefore recommended to accurately determine the NF1 status of such patients.
In conclusion, neurofibromas of the urinary bladder are extremely rare and often associated with NF1. Subtyping these lesions is difficult, and molecular testing for NF1 mutations is essential to guide diagnosis and management.
References
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