Older Male with Renal Mass

Specimen Type:



A 70-year-old man presented with a renal mass and underwent partial nephrectomy. Representative cross-sections were submitted.

Pathologic Features:

At low power, sections revealed two different populations of cells (Fig. 8.1-8.2). First, an oncocytic component composed of cells arranged in nests, tubules, and cysts with an edematous stroma (Fig. 8.3). The cytoplasm was eosinophilic and granular. The nuclei were mainly round with clumped chromatin and inconspicuous nucleoli (Fig. 8.4). The tumor cells were positive for CD117 (Fig. 8.5) and focally positive for CD10 (Fig. 8.6). They were negative for both vimentin and CK7.

Second, an adjacent 2mm nodule was identified and consisted of sheets and nests bounded by delicate vascular septa. The majority of cells contain abundant clear cytoplasm (Fig. 8.7). The nuclei were mainly punctuated with small nucleoli. These cells were positive for vimentin (Fig. 8.8) and CK7 (Fig. 8.9), negative for CD10 and CD117.

Differential Diagnosis:

  • Chromophobe Renal Cell Carcinoma (Fig.8.10)
  • Oncocytoma (Fig. 8.11)
  • Clear Cell Renal Cell Carcinoma (Fig. 8.12)

Chromophobe renal cell carcinoma: (Fig. 8.10) HE 400X Chromophobe renal cell carcinoma accounts for approximately 5 % of surgical removed renal epithelial tumors. It shows a peak incidence in patients in the sixth decade. Chromophobe renal cell carcinoma is usually a solid, circumscribed, homogeneously tan-colored tumor. Grossly visible necrosis is minimal to absent. The architecture shows sheets of cells divided by fine septa. The cells have either abundant granular eosinophilic cytoplasm or abundant, clear, finely reticulated cytoplasm. Most cases of chromophobe Renal cell carcinoma are nuclear grade 2. Hale’s colloidal iron stain stains the cytoplasm of chromophobe cells a vivid blue.

Oncocytoma: (Fig. 8.11) HE 100X Oncocytoma comprises approximately 5% of all neoplasms of renal tubular epithelium. It shows a peak incidence in the seventh decade of life. Males are affected nearly twice as often as females. It is a benign renal epithelial neoplasm composed of large cells with eosinophilic cytoplasm, thought to arise from intercalated cells. Oncocytoma is a well-circumscribed, nonencapsulated neoplasm, tan to pale yellow, presenting commonly with a central, stellate scar. Hemorrhage is present in up to 20% of cases. Grossly visible necrosis is rare. The tumor cells are arranged in nests, tubules, and cysts in a background of loose edematous stroma. The predominant cell-type is round-to-polygonal with densely abundant granular eosinophilic cytoplasm. The nuclei are mainly round with inconspicuous nucleoli, but occasional bizarre, enlarged nuclei may be seen. Mitotic figures are absent or very rare. Psammoma bodies are an unusual but occasional finding. Since it is benign, oncocytoma is not graded.

Clear Cell Renal Cell Carcinoma: (Fig. 8.12) HE 200X Clear cell renal cell carcinoma is a distinct subtype of renal cell carcinoma, possibly originating from mature renal tubular cells in the proximal tubule of the nehpron. It comprises 70-75% of renal cell carcinoma cases. They show a male preponderance of 2:1.

Grossly, the tumor is multicolored, with a predominantly yellow surface with white or gray foci. It usually shows a solid growth pattern, but in some cases cystic or alveolar appearance is seen. The cytoplasm is clear, due to an intensive intracytoplasmatic accumulation of glycogen and lipids. The nuclei are condensed and hyperchromatic.

Variants can be assigned which are characterized by augmentation of mitochondria leading to a stronger eosinophilia or granularity, respectively, of the cytoplasm. Spindle-shaped/pleomorphic variants as a result of sarcomatoid transformation can also be found.


Grade 2 (of 4) Clear Cell Renal Cell Carcinoma (0.5cm) and oncocytoma (1.5cm).

Immunostains for CK7, vimentin, CD10 and CD117 support this diagnosis.

Distinguishing features of oncocytoma, chromophobe RCC, and clear cell RCC

Neoplasm Oncocytoma Chromophobe RCC Clear Cell RCC
Distinguishing light microscopic features Nests, tubules; Edematous stroma; Eosinophilic and granular cytoplasm Sheets; Large polygonal cells; Prominent cell membranes; Perinuclear halo and reticular cytoplasm Compact alveoli, tublues; Prominent delicate vascualar network; Clear system
Distinguishing Histochemical features Hale's colloidal iron stain - Hale's colloidal iron stain + Hale's colloidal iron stain - Oil red O +
Distinguishing Ultrastructural features Numerous mitochrondria Numerous vesicles, 150-300nm in diameter Lipid and glycogen
Distinguishing Immunohistoche-mical features Vimentin - GST- alpha - CD117 + CK7 + (focal) EpCam + (focal) Vimentin - GST- alpha - CD117 + CK7 + (diffuse) EpCam + (diffuse) Vimetin + GST - alpha + CD117 -


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