Interinstitutional pathology consultations. A reassessment.

We retrospectively determined the clinical impact of 1,000 randomly selected interinstitutional pathology consultations (IPCs). An IPC included all specimens from the patient. IPCs were classified as concordant or discordant with the original diagnosis. Discordant IPCs were classified as having a clinical impact or no impact. Discordant IPCs owing to interpretation differences were subclassified further. The IPCs included 1,522 specimens (1,204 histology, 318 cytology); 923 (92.3%) were concordant, 9 (0.9%) indeterminate, and 68 (6.8%) discordant (clinical impact, 37; no impact, 31). Reasons for discordant IPCs were interpretation differences, 45; additional sectioning, 7; ancillary testing, 1; clerical error, 5; or a combination, 10. Reasons for 26 discordant IPCs with clinical impact owing to interpretation differences were overdiagnosis, 11; tumor subtype change, 4; stage change, 4; underdiagnosis, 3; resection margin status change, 2; undergrading, 1; and understaging with resection margin status change, 1. IPC may identify diagnostic discrepancies that impact management for some patients. The prevalence of a clinical impact of IPC on management varies according to body site. Mandatory IPC does ensure identification of clinically significant diagnostic discrepancies; targeted IPC by body site or specimen type may represent an alternative strategy after further data accumulation. Discordant IPCs may be due to factors other than interpretation difference.