Diagnostic accuracy and clinical outcomes of patients diagnosed with clear cell papillary renal cell tumour at renal mass biopsy

Background: Clear cell papillary renal cell tumour (CCPRCT) is a clinically indolent neoplasm. The diagnosis of CCPRCT at renal mass biopsy (RMB) may facilitate conservative management; however, this can be challenging in small samples and there are limited data on the outcome of patients managed conservatively. This study aimed to: (1) evaluate concordance between RMB and nephrectomy for the diagnosis of CCPRCT, and (2) determine the clinical outcomes of patients with CCPRCT, particularly those who have undergone conservative management. Methods and Results: We reviewed all cases at our institution where CCPRCT was diagnosed or included in the differential diagnosis at RMB. In all, 65 RMB with a diagnosis/differential diagnosis of CCPRCT were identified, including 25 patients who had subsequent surgical resection. Of cases where CCPRCT was the likely or favoured diagnosis on RMB (n = 19), the final diagnosis was concordant in 16/19 (84%). Discordant cases comprised clear cell renal cell carcinoma (ccRCC) (n = 1) and RCC with fibromyomatous stroma (n = 2). In all, 15 patients were managed with active surveillance (median follow-up 34 months) and 26 were treated with ablation (median follow-up 37 months). There was no recurrence, metastasis, or death in the cohort. Conclusion: CCPRCT can be reliably diagnosed at RMB in most cases if strict morphologic and immunohistochemical (IHC) criteria are applied. Furthermore, there was no adverse behaviour among patients managed nonsurgically in our cohort. It is important, however, to recognize the limitations of RMB, particularly given that occasional examples of ccRCC can show foci resembling CCPRCT. Pathologists and treating clinicians should be aware of the limitations of RMB when considering conservative management.