LAUSR

A 17-year-old Caucasian female with no urological history presented with a four-month history of intermittent visible haematuria associated with storage symptoms. She was treated with two courses of antibiotics but haematuria persisted. At the time of urological consult no abnormality was demonstrated on clinical examination. Baseline investigations included a normal full blood count and renal function. Bacteriology was also negative. She was further investigated with an ultrasound study and a computed tomography of the renal tract, which revealed a severely hydronephrotic left kidney, and a hydroureter where obstruction by an intraluminal mass was evident at the ureteric orifice (Figures 1 and 2). No lymphadenopathy or metastasis was detected. A dimercaptosuccinic renogram revealed a significantly reduced function of the left kidney to 5%. Subsequent cystoscopy showed a 3 cm tumour protruding from the left ureteric orifice which was resected. Attempts to perform a retrograde pyelogram, ureteroscopy and ureteric stenting were unsuccessful. On the grounds of a non-functioning kidney and risks of on-going haematuria, a laparoscopic nephroureterectomy was performed, during which a bladder cuff was resected. The nephroureterectomy specimen contained a pale-coloured, well-circumscribed solid lesion in the distal ureter (Figure 3), causing a near-complete upstream obstruction. The specimens from the cystoscopy and the nephroureterectomy showed haphazardly arranged interlacing fascicles of spindle cell proliferations within myxoid stroma (Figure 4). The cells lacked cytological atypia and showed occasional mitoses. The urothelium was normal. A lowgrade sarcoma was considered but the absence of malignant features assumed a more likely diagnosis of pseudosarcomatous myofibroblastic proliferation (PMP). The tumour cells were positive for smooth-muscle actin, myosin and focally (<10%) for AE 1/3 and CD34 (Figure 5). ALK-1 gene rearrangement, which is up to 70% prevalent in PMP,1 was not detected. A follow-up cystoscopy and magnetic resonance imaging of the abdomen were carried out at six months following the nephroureterectomy, both of which showed no signs of local or distal recurrence. A case of pseudosarcomatous myofibroblastic proliferation of the ureter causing obstructive nephropathy