OBJECTIVETo study the concordance rate of external pathology consultation referred by hospitals of various scales and to evaluate the value of such practice.

METHODSA total of 12 206 external pathology consultation cases referred by outside institutions were encountered during a 5-year period. The final pathologic diagnoses in 3289 cases were compared with the original interpretations. Each case was reviewed by at least two experienced pathologists. Immunohistochemical study was carried in selected examples. The pathologic findings were categorized as follows: (1) no diagnostic discrepancy, (2) minor diagnostic discrepancy and (3) major diagnostic discrepancy.

RESULTSAmongst the 12 206 cases studied, 7198 cases (59.0%) were sampled from the digestive tract, hematolymphoid system, soft tissue or breast. Seven thousand eight hundred and sixty-five cases (64.4%) were referred by small and medium-sized hospitals, while only 948 cases (7.8%) were referred by large hospitals (ranked IIIA). The diagnoses in 1842 cases (15.1%) were confirmed upon examination of the original paraffin sections, while the diagnoses in 2569 cases (21.1%) were made with cutting of additional sections from the paraffin blocks. On the other hand, the diagnoses in 7795 cases (63.8%) were arrived with the application of ancillary studies, including histochemistry and immunohistochemistry. Amongst the 3289 cases reviewed, diagnostic agreement was noted in 582 cases (17.7%), while major diagnostic discrepancy was observed in 113 cases (3.4%), including a change in diagnosis from "benign" to "malignant" in 31 cases (0.9%) and from "malignant" to "benign" in 38 cases (1.1%). The pathologic classification of the original diagnoses was modified in 44 cases (1.3%).

CONCLUSIONSExternal pathology consultation is useful for patient management in small and medium-sized hospitals, especially in resolving difficult and controversial pathologic diagnoses. Application of ancillary techniques, including immunohistochemistry, further helps to clear up the potential diagnostic dilemma.