Microscopic description and IHC:

Two distinct tumors are identified with intervening kidney parenchyma containing inflammatory cells. The smaller lesion shows cytoplasmic clearing and a “chicken-wire” vascular pattern and is CAIX, CD10, and vimentin positive, supporting a diagnosis of clear cell renal cell carcinoma. The larger lesion is eosinophilic with irregular nuclear borders and perinuclear clearing, negative for the aforementioned stains and positive for CK7 supporting a diagnosis of chromophobe renal cell carcinoma.

The inflammatory cells identified are located within the kidney parenchyma and stain positive for CD5, CD19, CD20, and CD23 and negative for CD10 supporting a diagnosis of B-cell small lymphocytic lymphoma/chronic lymphocytic leukemia (SLL/CLL). Furthermore, a lymph node identified within the specimen showed heavily pigmented histiocytes and small lymphocytes. Stains on the lymph node were positive for PAX5, CD5, CD23, and negative for BCL1 supporting the SLL/CLL diagnosis.

Discussion:

Clear cell renal cell carcinoma is the most common renal cell carcinoma. Grossly the lesion appears yellow-tan and can include cysts, hemorrhage, or necrosis. Cytoplasmic clearing and “chicken-wire” vasculature is seen microscopically. It is graded using Fuhrman grading, which takes into account the power at which one can see nucleoli and the atypia of the nucleus and cell borders.

Chromophobe renal cell carcinoma is the least common type of renal cell carcinoma. Grossly the lesion appears tan-brown and is usually well-circumscribed. The identifying feature is perinuclear clearing.

Small lymphocytic lymphoma/chronic lymphocytic leukemia is a common, low-grade malignancy that affects older individuals. Microscopically, one will see effacement of the normal lymph node architecture by small lymphoid cells and larger (1.5x the size of a lymphocyte) cells simulating germinal centers called proliferation centers. SLL/CLL can be further classified into various stages seen in the table below.

Table depicting levels of renal cell carcinoma
References:

Nucci, M. & Oliva, E. (2009). Gynecologic pathology a volume in the series foundations in diagnostic pathology. Edinburgh: Churchill Livingstone/Elservier.

Rosai, J. & Ackerman, L. (2011). Rosai and Ackerman's surgical pathology. Edinburgh New York: Mosby.

American Society of Hematology, Kay et. al. 2002, vol. 1:193, Table 8

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