Adenomatous Metaplasia Arising in a Horse-Shoe Kidney - A Rare Entity.

Urinary adenomatous metaplasia (nephrogenic adenomas) is uncommon, benign, apparently metaplastic response of the urothelium to chronic inflammation, trauma, surgery, urolithiasis, long-term indwelling urethral catheterization, and immunosuppressive therapy instillation. Gross or microscopic hematuria and some irritable urinary tract symptoms are often observed. A diagnosis is primarily based on the histopathological examination. We are reporting this case because adenomatous metaplasia is very rarely reported in the kidney especially in a horse shoe kidney with a large renal stone and these lesions could be mistakenly diagnosed as malignancy. In our knowledge this is the very first case of its kind. An awareness of this entity is critical to prevent over-diagnosis of cancer and to avoid unnecessary treatment.