FNAC Diagnosis of eosinophilic variant of chromophobe renal cell carcinoma – A challenge for cytopathologists

Chromophobe Renal Cell Carcinoma (ChRCC) is a rare distinct subtype of Renal cell carcinoma. It arises from intercalated cells of the renal cortex. The cytomorphological features of ChRCC show significant overlap with Clear cell Renal Cell Carcinoma (CCRCC) and Oncocytoma. The prognosis of ChRCC is intermediate between benign Renal Oncocytoma and the relatively aggressive CCRCC. Hence, a correct pre or intra-operative cytodiagnosis helps in deciding the extent of surgery. We report a case of eosinophilic variant of ChRCC in a 70 years female, diagnosed on Fine Needle Aspiration Cytology (FNAC).The Immunocytochemistry (ICC), histology and Immunohistochemistry confirmed the diagnosis of ChRCC. Diagnosing ChRCC; especially its eosinophilic variant on FNAC is very challenging. Prominent cellular heterogeneity, pleomorphism, perinuclear halos and binucleation are important diagnostic clues for cytodiagnosis of ChRCC. In difficult cases, ICC helps in confirming the diagnosis.

A CT-based radiomics nomogram for differentiation of renal oncocytoma and chromophobe renal cell carcinoma with a central scar-matched study

Objective: Pre-operative differentiation between renal oncocytoma (RO) and chromophobe renal cell carcinoma (chRCC) is critical due to their different clinical behavior and different clinical treatment decisions. The aim of this study was to develop and validate a CT-based radiomics nomogram for the pre-operative differentiation of RO from chRCC. Methods: A total of 141 patients (84 in training data set and 57 in external validation data set) with ROs (n = 47) or chRCCs (n = 94) were included. Radiomics features were extracted from tri-phasic enhanced-CT images. A clinical model was developed based on significant patient characteristics and CT imaging features. A radiomics signature model was developed and a radiomics score (Rad-score) was calculated. A radiomics nomogram model incorporating the Rad-score and independent clinical factors was developed by multivariate logistic regression analysis. The diagnostic performance was evaluated and validated in three models using ROC curves. Results: Twelve features from CT images were selected to develop the radiomics signature. The radiomics nomogram combining a clinical factor (segmental enhancement inversion) and radiomics signature showed an AUC value of 0.988 in the validation set. Decision curve analysis revealed that the diagnostic performance of the radiomics nomogram was better than the clinical model and the radiomics signature. Conclusions: The radiomics nomogram combining clinical factors and radiomics signature performed well for distinguishing RO from chRCC. Advances in knowledge: Differential diagnosis between renal oncocytoma (RO) and chromophobe renal cell carcinoma (chRCC) is rather difficult by conventional imaging modalities when a central scar was present. A radiomics nomogram integrated with the radiomics signature, demographics, and CT findings facilitates differentiation of RO from chRCC with improved diagnostic efficacy. The CT-based radiomics nomogram might spare unnecessary surgery for RO.

Renal Oncocytoma With Both Lymphovascular Invasion and Prominent Intracytoplasmic Vacuole-Like Spaces: A Case Report and Review of the Literature

Here we report a case of renal oncocytoma in a 68 year-old male. The diagnosis was initially made on a needle biopsy 6 years prior to the partial nephrectomy. The case is unique that in addition to the gross and microscopic features commonly seen in renal oncocytomas, both lymphovascular invasion and prominent intracytoplasmic vacuole-like spaces are also present in this tumor. Although vascular invasion is increasingly recognized as compatible with renal oncocytoma, intracytoplasmic vacuoles are a rare and unusual finding that may lead to diagnostic difficulty. The diagnosis of renal oncocytoma was confirmed after immunohistochemistry was performed to argue against succinate dehydrogenase deficient renal cell carcinoma (RCC) and chromophobe RCC. This case highlights the importance for practicing pathologists to recognize the rare co-occurrence of lymphovascular invasion and large intracytoplasmic vacuole-like spaces in renal oncocytoma. Other differential diagnoses may include emerging renal tumor entities, such as the recently-proposed eosinophilic vacuolated tumor.