We evaluated the clinicopathologic and chromosomal characteristics of a distinct subset of papillary renal tumors and compared them to a control series of papillary renal cell carcinoma types 1 and 2. Of the 18 patients, 9 were women and 9 were men, ranging in age from 46 to 80 years (mean, 64 y; median, 66 y). The tumors ranged in diameter from 0.6 to 3 cm (mean, 1.63 cm; median, 1.4 cm). Fourteen tumors were WHO/ISUP grade 2 and 4 were grade 1. All were stage category pT1. The tumors had branching papillae with thin fibrovascular cores, covered by cuboidal to columnar cells with granular eosinophilic cytoplasm, smooth luminal borders, and mostly regular and apically located nuclei with occasional nuclear clearing and inconspicuous nucleoli. Tubule formation and clear cytoplasmic vacuoles were observed in 5 and 9 tumors, respectively. Ten tumors had pseudocapsules. Psammoma bodies, necrosis, mitotic figures and intracellular hemosiderin are absent from all tumors. In contrast, papillary renal cell carcinoma type 1 consisted of delicate papillae covered by a single layer of cells with scanty pale cytoplasm with nuclei generally located in a single layer on the basement membrane of the papillary cores, while type 2 tumors had broad papillae covered by pseudostratified cells with eosinophilic cytoplasm and more randomly located nuclei. Both had occasional psammoma bodies, foamy macrophages and intracellular hemosiderin. Immunohistochemically, all were positive for pancytokeratin AE1/AE3, epithelial membrane antigen, MUC1, CD10, GATA3, and L1CAM. Cytokeratin 7 was positive in 16 tumors (1 had <5% positivity). CD117 and vimentin were always negative. α-methylacyl-CoA-racemase (AMACR/p504s) showed variable staining (range, 10% to 80%) in 5 tumors. However, all tumors in the control group were negative for GATA3 and positive for AMACR/p504s and vimentin immunostains. Fluorescence in situ hybridization analysis of the study group demonstrated chromosome 7 trisomy in 5 tumors (33%), trisomy 17 in 5 tumors (33%), and trisomy 7 and 17 in 3 tumors (20%). Chromosome Y deletion was found in 1 of 7 male patients and chromosome 3p was present in all tumors. No tumor recurrence or metastasis occurred. In summary, we propose the term papillary renal neoplasm with reverse polarity for this entity.

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Multiple confluent nodules, measuring 5.1 cm in maximum gross dimension. **No clinically malignant, pathologically benign (group E) cases were identified in the current series. DOD indicates died of disease; ETE, extratesticular extension; LVI, lymphovascular invasion; MF, mitotic figures per 10 HPF; NED, no evidence of disease; RPLN, retroperitoneal lymph node; S/P, status post.

AimsLow-grade oncocytic tumour (LOT) has recently been introduced as a potential distinct entity.MethodsAt the Indiana University department of pathology, primary renal epithelial neoplasms between 2005 and 2020 were searched after appropriate institutional review board permissions.ResultsTwenty-three cases (male/female ratio 14/9) with a median age of 66 (23–84 years) were identified. The majority of patients underwent partial nephrectomy (15/23, 65%), with a median tumour size of 4.0 cm (2.2–10.5 cm). Only one case had infiltration beyond the kidney (perinephric fat). Solid/diffuse proliferation of tightly packed oncocytic tumour cells and occasional tubule formations, with an abrupt edematous change in the stroma with loosely connected small clusters of tumour cells. Along with diffuse CK7 expression with lack of CD117 in all cases, vimentin was positive in 8/23 cases (35%, 5 focal). CD10 was expressed in 6/13 (46%, 4 focal). Alpha-Methylacyl-CoA Racemase (AMACR) was positive in 5/8 (63%) cases. Focal but intense cytoplasmic colloidal iron stain was present in 3/20 (15%) cases. Luminal or cytoplasmic/perinuclear precipitation was observed in 8/20 (40%) cases. Succinate Dehydrogenase B (SDHB) was performed in 6 cases, with all retained expression.ConclusionsLOT is a clinically indolent and potentially benign entity with distinguishable morphology and immunohistochemical profile that can be performed and be easily interpreted in most of surgical pathology settings. Additional studies with larger cohorts, comprehensive molecular evaluation and longer follow-up are needed to definitively recognise these tumours as a separate entity and to further address the possibility of active surveillance options in eligible patients.

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