Papillary clusters as a diagnostic pitfall in urinary cytology of pseudosarcomatous fibromyxoid tumor of the bladder. A case report.

BACKGROUND: Pseudosarcomatous fibromyxoid tumor (PFT) of the urinary bladder is an uncommon benign lesion that can involve any site in the bladder. Cellular features of PFT of the bladder are exceedingly rare. We describe the urinary cytology in a PFT patient who displayed numerous papillary fragments that suggested a malignant tumor. CASE: A 52-year-old man was seen at the hospital for evaluation of gross hematuria. At cystoscopy, the urologist observed a 3-cm, smooth, polypoid and ulcerated mass extending from the trigone to the bladder neck. Urinary cytology showed many papillary clusters with irregular nuclear margins in the bloody cell background. No spindle cells were noted. Cytology was interpreted as papillary growth, factor transitional cell carcinoma, grade 2-3. A laparotomy with partial resection of the urinary bladder was carried out, and histologically the tumor was composed of spindle, stellate, fibroblastic cells embedded in myxoid stroma with little collagen. Immunohistochemical and ultrastructural studies revealed the fibroblastic nature of the lesion. The final diagnosis was PFT of the bladder on the basis of histologic examination of the resected material. CONCLUSION: Papillary fragments are a diagnostic pitfall in urinary cytology of PFT lesions.