Pathologic Diagnosis:

Left kidney, renal mass, partial nephrectomy:
  • Metanephric Adenoma (3.4cm)
  • Immunostains performed at OSU:
    • Positive: PAX 8, WT1, CD57, CD56 (focal)
    • Negative: AMACR, CK7

Discussion:

Member of the metanephric tumor family, which also includes metanephric adenofibroma and metanephric stromal tumor

Most tumors have BRAF gene mutation

Benign tumor composed of cytologically bland embryonic looking epithelium with frequent psammomatous calcifications

Can be seen in patients from pediatric to older adult age

Considered to arise from different forms of maturation arrested embryonal rests, persistent blastema or maturing nephroblastoma due to its resemblance to nephrogenic rests / maturing Wilms tumor

Usually discovered incidentally with no presenting symptoms

If presenting with symptoms, it can demonstrate hematuria, pyrexia, flank pain, abdominal mass and polycythemia

Positive Stains: WT1, CD57, CD56 (Focal) and PAX8

Negative Stains: AMACR, CK7

References:

https://www.pathologyoutlines.com/topic/kidneytumormetanephric.html

CASE IMAGES