The impact of location and number of cores on the diagnostic accuracy of renal mass biopsy: an ex vivo study.

OBJECTIVE

To evaluate whether renal mass biopsy (RMB) biopsy location or number affected diagnostic accuracy in a prospective ex vivo study.

METHODS

Three cores (1 central and 2 peripheral) were obtained for histologic processing from each of 48 renal masses after nephrectomy. Individual biopsy cores were evaluated independently for tumor subtype and grade by a single, blinded GU pathologist.

RESULTS

Although individual biopsy cores were informative and confirmed accurate in only 59 % of samples, accuracy increased to 85 % with three-core biopsy (p < 0.01). Cancer identification with a single peripheral core increased to 77 % by adding a central core (p = 0.005), to 80 % with a second peripheral core (p = 0.008), and to 85 % with three cores (p = 0.001). Similarly, diagnostic yield for histologic subtyping increased from 44 % for 1-core biopsy to 59-63 % with 2-core biopsy (p = 0.03) and to 67 % with 3-core biopsy (p = 0.02). The correct subtype was confirmed at nephrectomy for 63 % of clear cell RCC, 60 % of papillary RCC, 100 % of chromophobe RCC and 75 % of oncocytomas. When recorded, nuclear grade corresponded to final grade assignment in 56 % and was within 1 grade in an additional 37 %.

CONCLUSIONS

RMB has not been used routinely in the evaluation of renal cortical neoplasms because of reportedly high rates of indeterminate or inaccurate diagnoses. In this prospective, ex vivo study, single-core RMB results in a low diagnostic yield. Obtaining multiple cores significantly improved diagnostic yield, with similar results with two-core and three-core RMB. We therefore recommend that RMB for suspicion of cancer include at least two peripheral cores.