Xp11 Translocation Renal Cell Carcinoma and the Mesenchymal Counterparts: An Evolving Concept with Novel Insights on Clinicopathologic Features, Prognosis, Treatment, and Classification

The TFE3 gene is one of four members of the micropathalima-associated transcription factor family, along with TFEB, TFEC, and MiTF, located on chromosome Xp11.2. The site is notable for its involvement in translocation in Xp11 translocation renal cell carcinoma (RCC) and the mesenchymal counterparts, including Xp11 neoplasm with melanocytic differentiation/TFE3 rearrangement-associated perivascular epithelioid cell tumor (PEComa)/ melanotic Xp11 translocation renal cancer/melanotic Xp11 neoplasm, and alveolar soft-part sarcoma. By morphologic, immunohistochemical, genetic, and prognostic similarities, alveolar soft-part sarcoma with the ASPSCR1-TFE3 gene fusion has a closer relationship with Xp11 neoplasm with melanocytic differentiation/TFE3 rearrangement-associated PEComa/melanotic Xp11 translocation renal cancer/melanotic Xp11 neoplasm. These Xp11 translocation mesenchymal neoplasms may represent a distinct entity, which overlaps with Xp11 translocation RCC and broadens the spectrum of Xp11 translocation-associated neoplasms. The impact of individual fusion variants on specific clinicopathologic features of Xp11 translocation RCC has only recently been described. This review provides insight into the clinicopathologic features, prognosis, treatment, and classification of Xp11 translocation RCC and its mesenchymal counterparts, emphasizing the impact of individual fusion variants on specific clinicopathologic features of Xp11 translocation RCC and the relationships among these Xp11 translocation-associated neoplasms.