Renal carcinomas with translocations involving MiTF/TFE family, which includes TFE3 (Ch Xp11.2) and TFEB (Ch 6p21).
TFE3 fuses mainly with ASPL [t(X;17)] or PRCC [t(X;1]), and each has unique morphological features.
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.
Previously, these tumors can easily be lumped with clear cell RCC because of the overlapped "clear cell" features.
ASPL-TFE3 carcinoma – has abundant or "voluminous" clear cell cytoplasm (image A) and psammoma bodies; less often papillary.
PRCC-TFE3 carcinoma – clear cell with papillary architecture (image B).
Alpha-TFEB carcinoma - dual population of larger clear cells forming nests and centrally has smaller cells clustered around hyaline nodules (image C).
Some tumors may also have eosinophilic cytoplasm.
Most are keratin– or focal+. (Unusual for epithelial tumor to have no keratin and contrasts to most RCCs).
Nuclear TFE3+ (image D) or TFEB+. (To confirm diagnosis and distinguish from other tumors, mainly clear cell RCC).
Melanoma markers (HMB45+ or MART1+). (Only other tumor in kidney that has this + is angiomyolipoma).
TFE3 carcinomas are suggested to be more aggressive, particularly when in adults, but data regarding behavior is still limited.
DDX: Clear cell RCC: lacks papillary architecture, voluminous cytoplasm, and second population of small cells, and is TFE3- and TFEB-.