Diagnostic challenges posed by lesions of adrenal origin in the assessment of renal tumor histopathology
Bibars W, Williamson SR, Hes O, Trpkov K, Montironi R, Aron M, Kaushal S, Ro JY, Smith SC, Roux J, Gandhi JS, and Amin M. Diagnostic challenges posed by lesions of adrenal origin in the assessment of renal tumor histopathology. Lab Invest 2018; 98:328-329.
Background: Intrarenal adrenal lesions are uncommon findings with variable clinical presentation that may range from an incidental abnormality discovered during nephrectomy, to symptomatic or asymptomatic radiologic lesions which result in nephrectomy. These findings may be broadly explained by either direct extension of an adrenal neoplasm into the kidney, or developmental abnormalities such as intrarenal ectopic adrenal tissue or renal-adrenal fusion that may develop neoplastic lesions. There is no comprehensive series of such cases that encompasses the spectrum of adrenal morphology and with emphasis on the differential with renal neoplasia. Design: We collected a large series of lesions of adrenal origin that involved the kidney and performed a detailed clinicopathologic analysis focusing morphologically on aspects that may mimic renal neoplasia. Results: 32 cases in the renal parenchyma /perinephric soft tissue were categorized as: 1. renal adrenal rests (n=16); 2. adrenal adenomas arising in the background of adrenal-renal fusion (n=7); 3. hyperplastic intrarenal adrenal rests resulting in pseudotumorous mass (n=3); 4. adrenocortical carcinomas secondarily involving the kidney (n=4); and 5. pheochromocytomas secondarily involving the kidney (n=2). Age ranged between 2 and 80 yrs. and lesions from 0.2 to 15 cm. Nested to trabecular architecture was present in almost all cases, with circumscription in 44%, and poor delineation/infiltration into the surrounding renal tissue in 56%. A clear cell predominant pattern was noted in 31% and an eosinophilic predominant pattern was present in 38%; 31% showed both eosinophilic and clear cells; 19% showed adrenal cortical and medullary tissue. 40% of the lesions were the primary indication for nephrectomy. 38% of lesions required diagnostic immunohistochemistry. A wide range of renal epithelial tumors, most commonly clear cell, chromophobe and unclassified renal cell carcinoma were in the differential diagnosis. Conclusions: Although rare, lesions of adrenal origin involving the kidney show significant morphologic mimicry with a wide spectrum of adult renal neoplasia. Awareness of these diagnostic challenges should raise consideration for them especially when dealing with renal masses that do not have histology typical of renal epithelial neoplasia. Our experience underscores the importance of the communication with clinicians, correlation with imaging findings and immunohistochemistry to accurately characterize the cases for appropriate management.