Clear cell papillary renal cell carcinoma and renal angiomyoadenomatous tumor: two variants of a morphologic, immunohistochemical, and genetic distinct entity of renal cell carcinoma

Clear cell papillary renal cell carcinoma as part of histologically discordant multifocal renal cell carcinoma: A case report and review of literature

BACKGROUND

Multifocal renal cell carcinoma of different histological subtypes within a single kidney is rare. We report a recently classified clear cell (tubulo) papillary renal cell carcinoma as part of an unusual case of multifocal renal cell carcinoma of discordant histological subtypes.

RESULTS

A 57 year-old-man was found to have multiple renal tumors and cysts on imaging and underwent a laparoscopic left radical nephrectomy. Pathological review showed multifocal renal cell carcinoma (clear cell (tubulo) papillary, clear cell and papillary renal cell carcinomas and papillary adenomas). Morphology of clear cell papillary renal cell carcinoma was supported by immunohistochemical profile (CK7+, HMWK+, CAIX+, AMACR-, CD10-, TFE3-).

CONCLUSIONS

This is the first report of clear cell papillary renal cell carcinoma as part of multifocal renal cell carcinoma of different histological subtypes. Related lineage of clear cell renal cell carcinoma and papillary renal cell carcinoma is supported by the highest prevalence of their combination within multifocal renal cell carcinoma of different histological subtypes along with their molecular interconnection. Clear cell papillary renal cell carcinoma may be uniquely placed between clear cell and papillary renal cell carcinomas since it shows morphological features intermediate between clear cell and papillary renal cell carcinoma along with overlapping but unique immunohistochemical profile. Clear cell papillary renal cell carcinoma may be molecularly related to clear cell and papillary renal cell carcinomas since the tumors overexpress markers of HIF pathway activation with normal/elevated VHL mRNA expression and some tumors show losses of chromosome 3. Due to the overlapping morphology, it is possible that cases of clear cell papillary renal cell carcinoma may have been misclassified as papillary or clear cell renal cell carcinoma in the literature, incorrectly increasing their reported prevalence. Identification of multifocal RCCs may be related to the extent of pathological sampling.

Emerging Entities in Renal Neoplasia

This article reviews emerging entities in renal epithelial neoplasia, including tubulocystic carcinoma, clear-cell-papillary renal cell carcinoma (RCC), thyroid-like follicular RCC, ALK-related RCC, translocation RCC, acquired cystic disease-related RCC, succinate dehydrogenase-deficient RCC, and hereditary leiomyomatosis-RCC syndrome-associated RCC. Many of these rarer subtypes of RCC were recently studied in more depth and are included in the upcoming version of the World Health Organization classification of tumors. Emphasis is placed on common gross and morphologic features, differential diagnoses, use of ancillary studies for making accurate diagnoses, molecular alterations, and predicted biologic behavior based on previous studies.

[Leiomyomatous renal cell carcinoma : Controversy around a new entity]

While clear cell, papillary and chromophobic renal cell carinoma (RCC) represent the most common malignant renal neoplasms, the evaluation and classification of rare renal carcinomas has currently come into focus. One of these is the leiomyomatous RCC, which shows morphologic similarities to clear cell RCCs, however exhibiting additional, atypical smooth muscle differentiation. We report the clinical case of a patient simultaneously presenting with leiomyomatous and papillary RCC and discuss new tumor entities of RCC.