Organ-associated pseudosarcomatous myofibroblastic proliferation with ossification in the lower pole of the kidney mimicking renal pelvic carcinoma: A case report

BACKGROUND: Organ-associated pseudosarcomatous myofibroblastic proliferation (PMP) is a very rare disorder. In the urogenital tract, PMP preferentially involves the urinary bladder; kidney involvement is rare. Here, we report a rare case of PMP with ossification in the lower pole of the kidney, which mimics urothelial carcinoma or an osteogenic tumor. CASE SUMMARY: A Chinese man was admitted to our hospital due to intermittent hematuria for more than 1 mo. Enhanced renal computed tomography revealed a mass in the left renal pelvis and upper ureter. The preoperative clinical diagnosis was renal pelvic carcinoma, determined by imaging examination and biopsy. After a standard preparation for surgery, the patient underwent retroperitoneoscopic radical nephroureterectomy. The operative findings were an extensive renal tumor (6 cm × 4.5 cm × 4.5 cm) invading the lower pole of the kidney and upper ureter. The final pathological diagnosis was organ-associated PMP with ossification. After 6-mo follow-up, no recurrence or metastasis was found. CONCLUSION: This case of PMP was unusual for its mimicking renal pelvic carcinoma in imaging examinations, making biopsy necessary.