Case of the Month

Answer to November’s Case of the Month

D. Fibroepithelial polyp

Fibroepithelial polyps (FEPs) are rare, benign, mesenchymal lesions, commonly found in the ureters and renal pelvis (1,2). Rarely, FEPs are bilateral. Approximately 70 percent of patients are males. FEPs may occur at any age (mean 40 years old) (3), but are the most common benign polypoid lesions of the ureters in children (4).

Clicky flank pain and hematuria are the most common symptoms. The etiology is uncertain (1,2), but the prognosis for patients with these lesions is excellent (5).

Grossly, FEPs consist of single or multiple slender, smooth-surfaced, vermiform polyps that usually arise from a common base. Microscopically, they are cloverleaf-like projections covered by urothelium; can be typical, reactive, or hyperplastic; and may be focally eroded. The core of the polyp comprises an edematous and vascular stroma with few inflammatory cells. Scattered atypical stromal cells may be present (5).

The differential diagnosis comprises urothelial papilloma (which has more slender papillae with secondary branching and prominent vacuolated umbrella cells), inflammatory polyps (which feature infection on the peripheral tissue and a rich blood supply with plentiful acute and chronic inflammatory cells), inverted papilloma (a predominantly epithelial lesion that has an endophytic growth with thin anastomosing cords), and florid cystitis cystica/glandularis (which lacks an exophitic papillary component, although FEPs may exhibit some endophytic nests identical to cystitis cystica/glandularis) (6).

Submitted by José Antonio Navarro Venebra, Hospital Civil de Culiacán, Sinaloa, Mexico.