Kidney and Adrenal Gland Cytology

Abstract

The critical role of fine needle aspiration (FNA) in the workup of the kidney and adrenal gland lesions continues to evolve and is also driven by current knowledge of the diseases as well as by clinical managements. Based on large-scale molecular studies and current knowledge, the WHO (World Health Organization) and ISUP (International Society of Urological Pathology) have updated the classification of urological lesions, particularly renal cell carcinoma (RCC); several newly recognized subtypes, including microphthalmia-associated transcription factor (MiT) family translocation (TFE3, TFEB, and MITF) RCC, are also documented as rare subtypes. Furthermore, the clinical detection rate of small renal masses (<4 cm in size) is on the rise, but the accurate diagnosis of these small masses still requires tumor tissue for morphological evaluation. Recently developed targeted therapies also demand that tumor tissue be obtained for molecular characterization. Therefore, an accurate diagnosis of a lesion and procurement of tumor tissue are critical steps in appropriate clinical management and the improvement of patients’ prognosis. Most FNAs are performed percutaneously through the abdominal wall anteriorly or by a flank approach posteriorly, under the guidance of CT, MRI, or ultrasound. In addition, endoscopic techniques, such as endoscopic ultrasound-guided FNA (EUS-FNA), are increasingly used in the biopsy of kidney and adrenal lesions in a subset of selected patients. As cytopathologists, we should understand the circumstances under which FNA is most often performed. This chapter summarizes the key FNA findings for cytomorphologic diagnosis of benign, malignant, and metastatic lesions of the kidney and adrenal gland.