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Collecting duct carcinoma of the kidney is a rare and aggressive subtype of renal cell carcinoma (RCC) arising from the distal convoluted tubules. At the time of diagnosis, patients are more frequently symptomatic, with advanced locoregional stage, and have metastatic disease. The 2016 WHO Classification of Tumours of the Urinary System defined diagnostic criteria for this entity. However, the diagnostic features continue to evolve, with typical, but not entirely specific, histologic and immunophenotypic characteristics. In addition, the lack of consistent molecular alterations makes collecting duct carcinoma a diagnosis of exclusion, with historical cases being re-classified as fumarate hydratase deficient RCC, ALK rearranged RCC, renal medullary carcinoma or high-grade urothelial carcinoma. The rarity and poor prognosis of the tumor makes it difficult to reach consensus guidelines to guide therapy. In this manuscript we review the clinicopathologic features of collecting duct carcinoma including pathologic diagnostic criteria, molecular characteristics and differential diagnosis, and their possible implications for management.

Objective To determine characteristics of the peritumoral pseudocapsule (PC) between renal tumor subtypes. Methods The peritumoral PCs of 160 pT1 renal tumors were examined, including 60 clear cell renal cell carcinomas (RCCs), 50 papillary RCCs, 25 chromophobe RCCs, and 25 oncocytoma. Pathologic features (presence or absence of PC, mean thickness, continuity, and invasion by tumor) were analyzed. PC thickness was measured using an ocular micrometer to the nearest 1/10 mm. Results A complete PC was found in 77% of clear cell tumors, 74% of papillary, 28% of chromophobe, and 4% of oncocytomas. Tumor PC was present but incomplete in 18% of clear cell, 18% of papillary, 44% of chromophobe, and 56% of oncocytoma. The PC was entirely absent in no clear cell tumors, 6% of papillary, 28% of chromophobe, and 40% of oncocytoma. Mean PC thickness and presence of invasion beyond the PC differed significantly by tumor subtype. Clear cell RCC possessed the thickest PC showing invasion through the capsule in 8% of tumors compared to 30% of papillary tumors. Complete PC invasion was not seen in chromophobe RCC or renal oncocytoma. Oncocytoma and chromophobe RCC characteristically exhibited an incomplete or absent PC. Conclusions The characteristics of peritumoral PC vary predictably with histologic subtype of renal neoplasms. Clear cell RCC shows the most consistent PC, with a lower rate of invasion beyond it compared to papillary RCC. Chromophobe and oncocytoma characteristically have an incomplete or absent PC.

Purpose The clinical significance of a positive surgical margin after partial nephrectomy remains controversial. The association between positive margin and risk of disease recurrence in patients with clinically localized renal neoplasms undergoing partial nephrectomy was evaluated. Materials and Methods A retrospective multi-institutional review of 1,240 patients undergoing partial nephrectomy for clinically localized renal cell carcinoma between 2006 and 2013 was performed. Recurrence-free survival was estimated using the Kaplan-Meier method and evaluated as a function of positive surgical margin with the log rank test and Cox models adjusting for tumor size, grade, histology, pathological stage, focality and laterality. The relationship between positive margin and risk of relapse was evaluated independently for pathological high risk (pT2-3a or Fuhrman grades III-IV) and low risk (pT1 and Fuhrman grades I-II) groups. Results A positive surgical margin was encountered in 97 (7.8%) patients. Recurrence developed in 69 (5.6%) patients during a median followup of 33 months, including 37 (10.3%) with high risk disease (eg pT2-pT3a or Fuhrman grade III-IV). A positive margin was associated with an increased risk of relapse on multivariable analysis (HR 2.08, 95% CI 1.09-3.97, p=0.03) but not with site of recurrence. In a stratified analysis based on pathological features, a positive surgical margin was significantly associated with a higher risk of recurrence in cases considered high risk (HR 7.48, 95% CI 2.75-20.34, p Conclusions Positive surgical margins after partial nephrectomy increase the risk of disease recurrence, primarily in patients with adverse pathological features.

There have been no recurrences or metastases of clear cell papillary renal cell carcinoma (CCPRCC) in 268 reported cases with follow-up in the English-language literature. We identified all our cases of CCPRCC (1990-2013), reviewing all cases that preceded the formal designation of the entity. Immunohistochemical stains were performed on 32 cases during their initial workup. In addition, stains for carbonic anhydrase IX and cytokeratin 7 were performed on 2 cases, one with atypical follow-up and the other with a more compact morphology, although not performed initially. An extended panel with AMACR, CD10, and renal cell carcinoma (RCC) was added to the case with atypical follow-up. Fluorescence in situ hybridization for chromosomes 3p, 7, and 17 was performed on the latter case and on another clinically presumed metastatic tumor. In classic cases, immunohistochemical staining was not performed. Fifty-eight patients (31 women; 27 men) with follow-up data were included in our study; 39 cases were from our consult service. The patients׳ ages ranged from 36 to 83 years. Thirty-five patients had cystic or partially cystic lesions; 6 tumors were multifocal, 3 of which were bilateral. The majority (53 patients; 91.4%) presented with stage pT1 disease (size range: 0.2-8cm), 2 patients presented with pT2 disease (8.5 and 10.3cm), 1 patient presented with pT3 disease (6.5cm sarcomatoid RCC focally extending out of the kidney), and pathologic stage was unavailable in 2 cases. Treatment consisted of 29 partial nephrectomies, 26 radical nephrectomies, 2 cryoablations, and 1 cyst ablation. The resection margins were negative in all but one case, with this case disease free after a 26-month period. Two patients had intraoperative tumor disruption and were disease free at 9 and 34 months. Five patients had synchronous ipsilateral renal cell carcinomas (non-CCPRCC). Mean follow-up time was 21 months (range: 1-175 months), with all but 3 patients having no evidence of disease. One patient was presumed to have contralateral disease on the basis of imaging findings and is alive and well 37 months after multiple partial nephrectomies. Metastatic disease to the lung was clinically presumed in 1 patient in whom a higher-grade lesion may have been missed during sampling of the predominantly cystic pT1b tumor and tissue confirmation of the metastases was not obtained. Another case presented with multiple skeletal and pulmonary metastases 8 months after resection of pT3 sarcomatoid CCPRCC. The patient with the sarcomatoid RCC died of multifocal skeletal and pulmonary metastatic disease 13 months after resection of the renal tumor. Our study, the largest to date with follow-up, along with others, suggests that pure CCPRCC is an indolent tumor and should be renamed "clear cell papillary neoplasm of low malignant potential" to reflect their biology.

Objective We evaluated survival outcomes of cystic/multilocular cystic renal cell carcinomas in a long-term population-based study based on size and pathological tumor stage. Materials and methods We, retrospectively, reviewed a provincial cancer registry of all histologically proven cases of multilocular cystic renal cancers treated surgically between 1995 and 2008. All cases of cystic necrosis were excluded from study. Primary end points were overall- and cancer-specific survival estimated using Kaplan-Meier curves. Cox proportional hazards models of univariable and multivariable analyses were used to assess for factors associated with survival. Results Of 172 cases of cystic renal cancers 168 with complete data were analyzed, of which 98% were multilocular cystic. Median patient age at treatment was 55 years and 58% of the patients were male. More than 40% of cases were pT1b or greater, 15% were pT2 or greater and most cases were low Fuhrman grade (1–2). At a median follow-up of 9.75-years overall- and cancer-specific survival was 82.1% and 100%, respectively. No difference was noted in higher pathological T stage, size, or grade. Limitations inherent in population-based studies include under ascertainment of cause of death, lack of data on histologically benign cysts that are treated surgically and a lack of central pathology review. Conclusions Multilocular cystic renal cell carcinoma has an excellent prognosis, which remains unchanged regardless of tumor size or pathological T stage. This suggests a strong case for nephron and adrenal sparing surgery when indicated, and nonsurgical management when feasible. As postoperative follow-up protocols are dictated by staging, we propose that for this entity pathological T staging should be abandoned or reassigned as pT1c to guide clinicians.