Symptomatic nephrogenic metaplasia of ureter: a morphologic and immunohistochemical study of four cases

Nephrogenic metaplasia of the bladder and urethra has been the subject of extensive studies in recent years. However, information about ureteral involvement is still limited because of the rarity of the lesion. We described four cases of nephrogenic metaplasia of the ureter. They occurred in two men and two women whose ages ranged from 46 to 69 years. Three patients had stones, and one had multiple episodes of cystitis and chronic pyelonephritis. The lesions led to ureteral obstruction that in two patients was radiographically suspicious for carcinoma. Microscopically, three lesions were composed of tiny mucin-containing microcysts and medium-sized tubular structures lined by cuboidal cells that showed cytologic atypia characterized by enlarged vesicular nuclei and prominent nucleoli. However, there were no mitotic figures. Two lesions invaded the full thickness of the wall of the ureter and exhibited an infiltrative growth pattern highlighted by cytokeratin stains. The remaining two lesions were confined to the lamina propria. The cells of nephrogenic metaplasia were immunoreactive to cytokeratin 7 and AE1-AE3. They lacked reactivity for monoclonal and polyclonal CEA and p53. The MIB-1-labeling index was <5%. The cytologic atypia and infiltrative growth pattern of ureteral nephrogenic metaplasia should not be misinterpreted as evidence of malignancy. All four patients are alive and symptom free 8 months to 7 years after diagnosis.