Best practices and recommendations for grossing and reporting of post-immunotherapy nephrectomy specimens: a single-institution experience of 70 cases

Abstract

The gross handling of and reporting of renal cell carcinoma in the setting of neoadjuvant immune checkpoint inhibitor therapy presents unique challenges, and there is little known about the spectrum of histologic changes that can be seen in this setting. We studied 70 cases of RCC, status post immunotherapy and nephrectomy at our institute and devised a standardized grossing protocol to help assess pathologic response. Our protocol includes sampling a complete cross section of the largest diameter of tumor with additional sections from areas of gross extrarenal involvement. Percentage of necrosis is calculated by assessing gross and microscopic necrosis and reporting an approximate average. Common histologic changes included fibrosis, myxoid change, necrosis and a chronic inflammatory infiltrate. Additionally, we found a discrepancy between the gross and the microscopic stages in 15 cases and all cases were of a lower pathologic stage than was suggested by the gross examination. We conclude that conventional staging guidelines may not apply to this unique cohort of cases, as using the gross estimate of tumor can falsely overestimate residual tumor burden. It is our recommendation to only assign a pathologic stage based on the location of the viable microscopic tumor. Before downstaging a tumor with grossly visible tumor outside the kidney, extensive sampling should be done in these areas to exclude microscopic tumor involvement.