Pelvic urothelial carcinoma with nested pattern of growth and an uncommon clinical presentation: a case report.

Background: Nested variant of urothelial carcinoma (NVUC) is a rare and often unrecognized urothelial neoplasia. Diagnosis is based on morphology only, and no immunohistochemical or cytogenetic differences from usual high-grade urothelial carcinomas have been reported.

Case: We describe the case of a 49-year-old woman affected by hepatitis C virus presented with fever, discomfort, urgency, and hypertension. Computed tomography showed a sclerosing inflammatory process involving the connective and adipose tissue of the renal sinus. In the absence of renal or pelvic masses an underlying malignancy was excluded and renal abscess or tuberculosis was suspected. Accordingly, nephrectomy and proximal ureterectomy was performed. Grossly, calices, renal pelvis, and pyeloureteral junction appeared modestly dilated with whitish, thickened, and uneven mucosa. Microscopically, the subepithelial connective tissue, the fibromuscular layer, and the renal sinus fat were diffusely infiltrated by small nests of medium to large urothelial cells (p63 positive) with abundant eosinophylic cytoplasm and slightly atypical nuclei.

Conclusion: On the basis of morphologic and immunohistochemical features, a diagnosis of NVUC was made. After surgery, the patient recovered from hypertension. Pelvic and upper urothelial tract NVUCs are uncommon, and to the best of our knowledge, this is the second case of NVUC with renal involvement.