Low-Grade Oncocytic Tumor (LOT): Clinicopathological, Morphological, Immunohistochemical and Cytogenetic Study of 17 Tumors

Eosinophilic/oncocytic tumors make up a large group of renal tumors that have been the focus of attention in recent years. Among them, low-grade oncocytic tumors stand out, characterized by their solid growth pattern and central edematous zone, keratin 7 positivity, and KIT negativity. Cytogenetically, they have been poorly categorized, although the most frequent findings are alterations in chromosomes 19 and 1. We present a relatively large series (17 tumors) with morphologic, extensive immunohistochemical, cytogenetic, and clinical outcomes. In the series under investigation, the frequency of low-grade oncocytic tumors was 6.8% out of all oncocytomas and chromophobe tumors, especially among the latter, reaching just over 10%. Morphologically, in addition to the features already reported in the literature, central and thick-walled vessels and hyaline globules were observed. Immunohistochemically, there was nuclear positivity for GATA3 in 17 out of 17, and 1 tumor presented nuclear positivity and cytoplasmic staining. Cytogenetically, the majority of neoplasms (14 out of 17) were disomic, although 3 of them had trisomy for chromosome 7. With a median survival of nearly 5.5 years after the surgery, no recurrence or metastasis was detected, confirming the excellent prognosis of this type of tumor.