Microscopic description:

On low power, the tumor shows lobular/nested appearance with fibrous septae. On high power, it shows a papillary growth pattern with cells showing clear to eosinophilic cytoplasm, high grade nuclei and prominent nucleoli.

Differential diagnosis includes clear cell renal cell carcinoma, clear cell papillary renal cell carcinoma, epithelioid angiomyolipoma and clear cell sarcoma.

IHC showed positive staining for TFE3, SDHB, AMACR, HNF1, AE1/AE3 (weak,focal), PAX8, INI1 and negative staining for CAIX, OCT3/4, CK7. Based on microscopic features and IHC, the tumor shows features consistent with renal cell carcinoma, MITF/TFE3 family translocation associated subtype.

Discussion:

The MiT family translocation renal cell carcinoma comprises Xp11 translocation renal cell carcinoma harboring TFE3 gene fusions and t(6;11) renal cell carcinoma harboring TFEB gene fusion

Uncommon, but with relatively higher incidence in pediatric patients and young adults.

A small subset may develop in young patients with past exposures to chemotherapy for childhood malignancies

Patterns and cells may vary according to the precise translocation involved

Large vesicular nuclei

  • Prominent round nucleoli
  • Mitotic figures frequent

Features frequently present

  • Psammoma bodies may be abundant
  • Intracytoplasmic hyaline droplets

May contain melanin pigment and express melanocytic markers

ASPL-TFE3 carcinoma – has abundant or "voluminous" clear cell cytoplasm and psammoma bodies; less often papillary.

PRCC-TFE3 carcinoma – clear cell with papillary architecture. Alpha-TFEB carcinoma - dual population of larger clear cells forming nests and centrally has smaller cells clustered around hyaline nodule.

Some tumors may also have eosinophilic cytoplasm. The most sensitive and specific immunohistochemical marker for the Xp11 translocation RCC is strong nuclear TFE3 staining. Melanoma markers (HMB45+ or MART1+), negative for CK 7, EMA, CD117.

Translocation carcinoma should be considered in the following situations

  • Any clear or papillary renal carcinoma in a patient under 35
  • Any carcinoma combining papillary with clear cell features
  • Any carcinoma with nests of cells with voluminous cytoplasm
  • Any carcinoma with large numbers of psammoma bodies
References:

Caliò A, Segala D, Munari E, Brunelli M, Martignoni G. MiT Family Translocation Renal Cell Carcinoma: from the Early Descriptions to the Current Knowledge. Cancers (Basel). 2019 Aug 3;11(8):1110. doi: 10.3390/cancers11081110. PMID: 31382581; PMCID: PMC6721505.

Argani P. MiT family translocation renal cell carcinoma. Semin Diagn Pathol. 2015 Mar;32(2):103-13. doi: 10.1053/j.semdp.2015.02.003. Epub 2015 Feb 4. PMID: 25758327.

https://www.auanet.org/education/auauniversity/education-products-and-resources/pathology-for-urologists/kidney/renal-cell-carcinomas/mitf/ttf-translocation-associated-carcinoma

http://surgpathcriteria.stanford.edu/kidney/mit-translocation-renal-cell-carcinoma/printable.html

CASE IMAGES