Contributed by Daniel Geisler, MD, MS and Gabriela M. Quiroga-Garza, MD
The patient is a female in her 70s with a history of papillary thyroid microcarcinoma status post lobectomy who presents with a 2.9 cm mass of the left kidney upper pole. An incidental mass was found on imaging three years ago, initially showing a 2.4 cm nodule with heterogeneous attenuation and enhancement post contrast administration. She denied any symptoms, smoking history, or family history of urological malignancies. Due to the increase in size, the patient elected to undergo a laparoscopic partial nephrectomy of the mass.
The specimen measures 2.1 x 2.0 x 1.7 cm and consists of a well-defined, partially cauterized, enucleated, and encapsulated lesion. Attached adipose tissue and scant amount of apparent normal renal parenchyma are also attached. The cut surface shows a well-defined, glistening, tan-white-brown, rubbery, and partially cystic mass with no obvious necrosis (Figure 1).
The lesion is well-circumscribed with varying cystic, acinar, tubular, and papillary patterns of architecture (Figure 2A-B). The cells are cuboidal to columnar with clear cytoplasm. The nuclei are generally uniform, small, and round with inconspicuous nucleoli arranged away from the basal aspect of the cell (Figure 2C-D). The scant stroma is composed of loose fibroconnective tissue with edematous areas with focal chronic inflammatory infiltrate. Tumor necrosis, sarcomatoid/rhabdoid changes, lymphovascular invasion, and perirenal invasion are not identified.
Immunohistochemical stains performed on the tumor show CK7 (Figure 3A-B), carbonic anhydrase-9 positivity (Figure 3C-D), and pancytokeratin positivity. The tumor is negative for AMACR/P504s, RCC, CD10 and TTF-1.