PMC10151571_01
(A-E) Histomorphological features of papillary renal neoplasm with reverse polarity. The tumor is well defined, with a fibrous pseudocapsule and many lymphocyte infiltrates at the capsule margin (H&E stain, x40) (A). It showed a slender papillary structure with local tubular papillary branches (H&E stain, x40) (B). Low-grade nuclei, inverted linear nuclear location (H&E stain, x200) (C). A few foamy macrophages are observed in the stroma (H&E stain, x100) (D). Osseous metaplasia was locally visible in the tumor (H&E stain, x200) (E).
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Microscopically, the tumor was clearly demarcated, with a fibrous pseudocapsule, and multiple lymphocytic infiltrates were present at the capsule edge ( Figure 1A ). Papillary branching was visible, with a few large papillae and others edematous ( Figure 1B ). Their nucleoli were inconspicuous, corresponding to the WHO/ISUP grade 1, and no mitotic figures were noted ( Figure 1C ). Figure 1D ). Focal papillary stroma underwent hyaline degeneration. Osseous metaplasia was locally visible in the tumor ( Figure 1E ).
(A-F) Immunohistochemical profiles of papillary renal neoplasm with reverse polarity. The tumor cells are positive for GATA-3(x200) (A), KRT7(x200) (B), 34betaE12(x200) (C), Ksp-Cadherin(x200) (D), AMACR(x200) (E), and Vimentin(x200) (F); however, the staining intensities varied.
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Immunohistochemically, nearly all tumor cells expressed GATA-3, KRT7, EMA, 34betaE12, E-cadherin, Ksp-Cadherin, and AMACR ( Figures 2A-E ).
The KRAS mutation status of the papillary renal neoplasm with reverse polarity. Real-time fluorescent quantitative polymerase chain reaction analysis showed the KRAS mutation was present in exon 2-codon 12: p.G12V (c.35 G >T).
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Figure 3 ), while no NRAS or BRAF V600 mutation was detected. Finally, we made the pathological diagnosis of papillary renal neoplasm with reverse polarity (PRNRP) for the tumor.