[851] Nephrogenic Adenoma: A Report of 3 Unusual Cases Infiltrating into Perinephric Adipose Tissue

Mairo Diolombi, Francesca Mercalli, Jonathan I Epstein. George Washington University Medical Center, Washington, DC; Facoltà di Medicina e Chirurgia Università del Piemonte Orientale Amedeo Avogadro, Novara, Italy; Johns Hopkins Hospital, Baltimore, MD

Background: Nephrogenic adenomas are believed to result from exfoliated renal epithelial cells that then become implanted in the urinary tract at the site of prior injury. They most frequently involve the urinary bladder, where they are typically confined to the lamina propria but can on occasion focally involve the superficial muscularis propria. There have been 34 reports of nephrogenic adenomas in the ureter with only 4 cases describing involvement of the muscularis propria to varying extents. None have been deep-seated lesions involving the perinephric adipose tissue mimicking carcinoma.
Design: We identified three consult cases where tubules of nephrogenic adenoma extensively involved the muscularis propria and focally infiltrated the perinephric adipose tissue, where the contributing pathologists considered the diagnosis of adenocarcinoma.
Results: In one case, from a 71 year-old man, the lesion was associated with a hemorrhagic renal cyst (3.0 cm) and a spontaneous retroperitoneal bleed (6.0 cm) of unknown origin. The tubules were positive for CK7 and PAX8 and negative for AMACR and GATA3. The 2nd case, in a 73 year old woman, had two foci (2.2 cm, 1.6 cm) in the renal pelvis. They occurred following biopsy of a low grade non-invasive papillary urothelial carcinoma in the same site complicated by perforation. The tubules were positive for CK7, PAX8, AMACR, and negative for GATA3. The 3rd case was in a 20 year old woman with ureteropelvic junction obstruction and severe hydronephrosis associated with renal calculi. In this case, the lesion was positive for CK7, PAX8, and AMACR and had a high ki67 (30%) proliferative index.
Conclusions: Pathologists should be aware that nephrogenic adenoma can have a deep infiltrating pattern into perinephric adipose tissue especially when arising in the ureter or in the renal pelvis. These lesions possibly are a result of either biopsy associated perforation or extensive disruption due to hemorrhage or mechanical obstruction. Whereas urothelial mimickers of carcinoma, can involve the lamina propria yet not the muscularis propria, glandular mimickers of carcinoma such as nephrogenic adenoma can extend more deeply into the muscularis propria. This report is the first to describe that in exceptional cases in the renal pelvis and ureter, nephrogenic adenoma can involve the full thickness of the muscularis propria and the surrounding adipose tissue.
Category: Genitourinary (including renal tumors)

Wednesday, March 6, 2013 9:30 AM

Poster Session V # 134, Wednesday Morning


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