Microscopic description:

The tumor is solid cystic with tumor cells are arranged in papillary, tubular and solid sheet like pattern in hyalinized stroma at places.

The tumor cells are predominantly monomorphic, cuboidal to columnar with small, round to oval nuclei with regular nuclear membranes and inconspicuous to small nucleoli. The nuclei are localized toward the luminal surface and away from the basement membrane, namely reverse polarity with clear to pale eosinophilic cytoplasm.

On IHC- Tumor cells are positive for CK7, cup like staining pattern with CA IX, PAX 8 and negative for AMACR and CD10.

Discission:

This was introduced as new tumor entity in 2016 because of its unique morphology, immunohistochemical profile, genetic features and clinically indolent behavior.

Nearly all tumors are pT1.

It is crucial to differentiate it from other subtypes of renal cell carcinoma as others have much worse prognosis.

This tumor lacks chromosome 3p loss and alterations of VHL with no mutations in TSC1, TSC2, MTOR, TCBE1.

Table depicting IHC chart
References:

Williamson S R et al. Clear cell papillary renal cell carcinoma: differential diagnosis and extended immunohistochemical profile. Mod Pathol, 2013 May;26(5):697-708.

Kuroda N et al. Clear cell papillary renal cell carcinoma: a review. Int J Clin Exp Pathol. 2014;7(11):7312-7318.

Zhao J. Clear cell Papillary renal cell carcinoma. Arch pathol Lab Med(2019) 143(9):1154-1158.

Tordjman M et al. Clear cell papillary renal cell carcinoma: A Recent entity with distinct imaging patterns. Am J Roentgenol. 2020 Mar;214(3):579-587.

CASE IMAGES