The fine needle aspiration (FNA) cytology, either under CT- (computed tomography) or ultrasound-guidance, is a commonly used approach to obtain samples from renal and adrenal lesions. This chapter is focused on the discussion and review of cytomorphology of FNA specimens of benign and malignant diseases of the kidney and adrenal gland. Although the differential diagnosis of a kidney mass is broad, including both primary and metastatic tumors, the majority of kidney masses are primary kidney tumors. Whereas, in adrenal masses, the majority of tumors are metastatic tumors rather than primary adrenal tumors. The limitations of the FNA cytology in the diagnosis of renal and adrenal lesions are also discussed in the chapter. For example, the cytological differentiation of an oncocytoma from a chromophobe renal cell carcinoma may be difficult due to overlap cytomorphology. Nevertheless, the most renal and adrenal lesions can be accurately diagnosed by FNA cytology.
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