A 50-year-old patient with a history of recurrent renal lithiasis presented with recurrent hematuria and feeling unwell.
Serial urine cytological study showed the presence of malignant melanoma cells.
Imaging studies revealed a heterogeneous lesion occupying almost the entire right renal pelvis.
Nephrectomy was performed due to total consistency and partial resection blanda kidney cut of 10.5 cm with maximum dimensions that showed an irregular and heterogeneous lesion of brown color in the renal pelvis.
This relatively well-defined lesion does not affect the parenchyma or the renal sinus, but is limited to the foot-located system with expansive margins compressing the cortex in one of the renal poles.
The histological study showed that the lesion consisted of well-defined tumoral nests without evidence of invasion of the renal parenchyma, encompassing a central mucinous matrix which constituted more than 50% of the tumor volume.
In the heart of the matrix, these cells were floating and their nests were smaller than those located at the peripheral level.
Tumor cells showed polygonal morphology with central nuclei not apparent and low atypia as well as eosinophil and clear cytoplasms.
In the delimiting areas with the mucinous matrix, there was a temporomandibular disorder glandular differentiation with the observation of some components and a slight increase in nuclear atypia.
Tumor cells showed intense immunopositivity for EMA, CK 7 and mild immunopositivity for CK20, confirming the urothelial nature of the neoplasm.
With all the exposed data, the diagnosis of low-grade transitional cell carcinoma with intense mucinous differentiation of the renal pelvis (colloid carcinoma) was made.
