Kidney tumor

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Contributed by Debra L. Zynger, M.D.

Contributed by Tatjana Antic, M.D. and @katcollmd on Twitter

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• Papillary renal cell carcinoma, particularly solid variant:
  • Less tightly packed tubules, appears less basophilic
  • Usually has foamy macrophages
  • Vimentin+, PAX8+, CK7+, AMACR+, WT1-, CD57-, BRAF- (Mod Pathol 2015;28:1236)
• Metanephric-like ALK rearranged renal cell carcinoma:
  • Morphology is similar to metanephric adenoma with small tubules, some of which are elongated
  • Metanephric adenoma-like morphology seen in 1 case only at the periphery, with the rest of the tumor being morphologically heterogeneous
  • Vimentin+, PAX8+, CK7+, ALK+, AMACR+, BRAF-, CD57-, WT1- (Mod Pathol 2020;33:2564, Virchows Arch 2020;476:921)
• Nephroblastoma:
  • More difficult to differentiate if tumor is monophasic, composed of a blastema component only
  • PAX8+, WT1+, vimentin-, CD57-, BRAF- (Mod Pathol 2015;28:1236)
• Metastatic thyroid carcinoma, particularly poorly differentiated:
  • Malignant cells might have nuclear grooves and pseudonuclear inclusions
  • PAX8+, TTF1+, BRAF+, WT1-

A 66 year old woman with flank pain is found to have polycythemia. The CT scan shows a 3.8 cm solid, circumscribed and hypovascular renal cortical tumor. Which of the following renal tumors is likely to be associated with this clinical presentation, imaging study and the histomorphology shown above?


1. Angiomyolipoma, triphasic
2. Clear cell renal cell carcinoma
3. Metanephric adenoma
4. Nephroblastoma
5. Urothelial carcinoma

C. Metanephric adenoma is associated with polycythemia and a hypovascular renal mass on imaging. The section shows a well circumscribed renal tumor composed of tightly packed tubules. Answer A is incorrect because angiomyolipoma contains adipose tissue, which is easily seen on CT scan. Answer D is incorrect because the patient’s age argues against the diagnosis of nephroblastoma. Answer E is incorrect because urothelial carcinoma is neither a cortical tumor nor is it circumscribed. Answer B is incorrect because clear cell renal cell carcinoma is a hypervascular tumor, although it can cause polycythemia and is not basophilic.

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Reference: Metanephric adenoma

A renal mass from a 43 year old woman shows a tumor composed of tightly packed basophilic tubules. The cell nuclei are cytologically bland and cytoplasm is scant. Numerous psammomatous calcifications are present. No mitotic activity or necrosis is present. Which of the following is the immunohistochemical profile that should be seen in this tumor?


1. PAX8+, WT1+, CK7-, CD57+, BRAF+
2. PAX8-, WT1+, CK7-, CD57+, BRAF-
3. PAX8+, WT1+, CK7-, CD57+, BRAF-
4. PAX8+, WT1-, CK7-, CD57+, BRAF+
5. PAX8+, WT1-, CK7+, CD57+, BRAF+

A. PAX8+, WT1+, CK7-, CD57+, BRAF+. This is a metanephric adenoma. The differential diagnoses include papillary renal cell carcinoma, type 1, solid variant and adult epithelial predominant nephroblastoma. Papillary renal cell carcinoma, type 1 is a PAX8+, vimentin+, CK7+, AMACR+, WT1-, CD57-, BRAF- tumor, as opposed to metanephric adenoma, which is positive for WT1, CD57 and BRAF and negative for CK7. Adult nephroblastoma is positive for WT1 but negative for CD57 and BRAF.

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Reference: Metanephric adenoma