Renal Mass in Young Adult Man

Deloar Hossain, M.D.

Specimen Type:

Kidney

History:

A 31-year-old man with a clinical diagnosis of renal carcinoma underwent a wedge resection of kidney. At surgery, a circumscribed, soft, tan, hemorrhagic tumor was identified measuring 2.3 cm x 1.7 cm that bulged but did not appear to invade the capsule. The remaining renal parenchyma was grossly unremarkable. Representative cross-sections were submitted.

Pathologic Features:

Sections revealed a well-circumscribed tumor consisting of cells arranged in nests, tubules, and cysts with an edematous stroma ( fig 1.1 HE 40X ). The cytoplasm was abundant, eosinophilic, and granular, and the nuclei were mainly round with conspicuous nucleoli ( fig 1.2 HE 200X ). Occasional bizarre nuclei were seen ( fig 1.3 HE 400X ). Prominent number of psammoma bodies were present in the stroma ( fig 1.4 HE 400X ). Tumor cells showed membranous immunoreactivity for CD117 ( fig 1.5 400X ). Hale’s colloidal iron stain was negative (fig 1.6 400X ).

Differential Diagnosis:

  • Chromophobe Renal Cell Carcinoma (fig 1.7 HE 400X ),
  • Oncocytoma (fig 1.8 HE 100X ),
  • Papillary Renal Cell Carcinoma (fig 1.9 HE 200X & HE 400X ), and
  • Metanephric adenoma (fig 1.10 HE 200X & HE 400X ).

Diagnosis:

Oncocytoma with Psammoma bodies

Key Features:

  • Benign renal epithelial neoplasm with a peak incidence of 65 years at presentation
  • Often discovered incidentally by radiologic examination of the kidneys during workup for unrelated conditions
  • Usually unilateral, solid, well circumbscribed but nonencapsulated round mass with pushing borders
  • May have central stellate zones of white or pale gray stroma that connects with the periphery
  • Composed of cells arranged in diffuse sheets or as cellular islands in a background of loose edematous stroma
  • Tumor cells are round-to polygonal with densely granular eosinophilic cytoplasm; nuclei are mainly round with inconspicuous nucleoli. Occasional foci of “degenerative” nuclear atypia with pleomorphism may be observed
  • Calcification, including psammoma bodies are uncommon; they are usually seen in association with either papillary areas or hemorrhage
  • Negative Hale’s colloidal iron stain
  • Mitotic figures, papillary architecture, clear or spindle cells, gross vascular invasion and gross extension into perirenal fat are almost never seen
  • Overexpression of KIT (CD117) can be useful as an immunophenotypic marker
  • Usually negative for cytokeratin 7
  • Resection of the tumor is curative

References:

  1. Pann CC, Chen PC, Chiang H. Overexpression of KIT (CD117) in chromophobe renal cell carcinoma and renal oncocytoma. Am J Clin Pathol. 2004; 121(6):878-83.
  2. Tickoo SK , Amin MB. Discriminant nuclear features of renal oncocytoma and chromophobe renal cell carcinoma. Analysis of their potential utility in the differential diagnosis. Am J Clin Pathol. 1998; 110(6):782-7.
  3. Perez-ordonez B, Hamed G,Campbell S, et al. Renal oncocytoma: a clinicopathologic study of 70 cases. Am J Surg Pathol. 1997; 21:871-883.
  4. Amin MB , Crotty TB, Tickoo SK, et al. Renal oncocytoma: reappraisal of morphologic features with clinicopathologic findings in 80 cases. Am J Surg Pathol. 1997;21:1-12.