Mesonephric adenoma in remnant ureteric stump: A rare entity.

Nephrogenic Adenomas have been reported though out the Urinary Tract from Renal Pelvis to the Urethra. We present one rare case of its occurrence in the remanant ureteral stump.

INTRODUCTION

Nephrogenic adenoma (NA) is a rare benign condition of the urinary system. It is also known as mesonephric adenoma. Friedman and Kuhlenbeck reported eight similar cases of adenomatoid tumors and coined the term “Nephrogenic Adenoma” to describe the resemblance of these lesions w the developing kidney and their possible neoplastic potential. NAs have been reported throughout the urinary tract, from the renal pelvis to the urethra, the most common site being the bladder (71%). However, many cases have been reported in the ureters as well.[1]

CASE REPORT

An 18-year-old male patient presented with chief complains of painless hematuria of 4 days duration. There were no other significant complaints. The patient had undergone right-sided radical nephrectomy 4 years back (histopathology of resected kidney revealed renal papillary cell carcinoma). General and systemic examinations revealed no abnormality, except for the presence of a right-sided flank scar. Ultrasonography revealed the presence of a 2 cm × 2 cm mass in relation to the right ureteric orifice. Microscopic examination of the urinary sample did not reveal the presence of any malignant cells. Hematological and biochemistry examinations were within normal limits. Cystoscopy revealed a polypoidal mass protruding out of the right ureteric orifice, and this mass was resected [Figure 1]. Histopathology of the resected tissue was suggestive of NA. Excision of the ureteric stump with bladder cuff was performed [Figure 2] and histopathology of the excised mass revealed mesonephric tubules, usually lined by a single layer of bland cuboidal or hobnail cells. Cells had clear or eosinophilic cytoplasm, small nuclei and no prominent nucleoli with thickened basement membrane. Stromal edema and inflammatory infiltrate were also seen, which were suggestive of NA [Figure 3].

Figure 1

Resected right ureter with mass seen at its lower end

Figure 2

Cystoscopic picture of the polypoidal mass protruding from the right ureteric orifice

Figure 3

Histologically, mesonephric tubules lined by a single layer of bland cuboidal surrounding eosinophilic secretions. Cells had eosinophilic cytoplasm, small nuclei and no prominent nucleoli with thickened basement membrane. Stromal edema and inflammatory infiltrate were present

DISCUSSION

NA, or mesonephric adenoma, is a rare benign lesion of the urothelial tract. The etiology of NA is not well defined. Various factors implicated in the occurrence of this pathology are:

Chronic inflammation — secondary to trauma, infection, catheterization, postoperative.[2]

Metplastic changes in the transitional epithelium due to invagination of the mesodermal cells in the embryologic bladder.[3]

Transplantation of the renal tubular epithelial cells in the urinary tract.[4]

On light microscopy, NA shows a variety of patterns, including tubulocystic, papillary and, much less frequently, solid, which often coexist. Recognition of its characteristic patterns and awareness of its unusual architectural and cytologic features is key to making the diagnosis of NA and distinguishing this lesion from malignant neoplasms occurring at the same sites, in particular, clear cell carcinoma, nested or microcystic variants of urothelial carcinoma and prostatic adenocarcinoma. Although straightforward in most cases, the correct diagnosis may be difficult to make on limited tissue samples. A number of immunohistochemical markers have been studied in an attempt to characterize NA; however, to date, there is no specific immunohistochemical profile to distinguish this lesion from its malignant mimickers, although PAX2, a new marker, may prove to be helpful in this regard.[5] Epstein et al. presented the first report of a fibromyxoid subtype of NA. Nephrogenic metaplasia, focal and diffuse have also been recorded, and this is seen more often in children than in adults, where adenoma predominates.[4]

Treatment for NA is endoscopic resection. However, due to the risk of local recurrence, follow-up examinations must be emphasized upon.