ABSTRACT
OBJECTIVES: To evaluate interobserver reproducibility of a combined scoring method for immunohistochemical interpretation of p16 overexpression in cervical lesions. MATERIALS AND METHODS: p16 immunostaining was performed in cervical samples from 183 patients, including 69 normal, 42 low grade squamous intraepithelial lesions(LSIL), 36 high grade SIL (HSIL), and 36 squamous cell carcinomas(SCCAs). Each case was evaluated by a combined scoring method based on the percentage of positive cells (score 0-3), the intensity of staining (score 0-3), and the distribution pattern (score 0-2). Immunoexpression for p16 was considered as positive when the combined score was 4-8 and negative with a score of 0-3. Ten pathologists with varied experience in interpretating p16 immunostains evaluated each slide independently. RESULTS: All normal cervical squamous epithelia (69/69) were uniformly negative for p16. All HSILs (36/36), all SCCAs (100/100), and all but one of the LSILs (40/41, 97.6%) showed positive expression. In 172 of 183 cases (93.9%), p16 interpretation was concordant with all pathologists. Eleven cases with discordant results included 10 LSILs and 1 normal mucosa sample. Percentage of agreement of each pathologist pair ranged from 96.7-100% (mean 98.1%) with mean kappa value of 0.96 (range 0.93-1.000). CONCLUSION: The proposed combined scoring method shows good reproducibility among the participating pathologists and good correlation with the histologic diagnosis. This method may be a useful guide in the interpretation of p16 expression in cervical epithelial lesions.
ABSTRACT
OBJECTIVES: To develop and verify a standardized protocol for HER2 immunohistochemical assays on invasive ductal carcinoma of the breast in Thailand. MATERIAL AND METHOD: A two-phase study approach was employed. In the Phase One, after verifying the proposed protocol that adopted the HercepTest procedure using readily available primary antibodies, CB11 and A0485, Lab 1 performed the HER2 immunohistochemical staining for 137 cases of invasive ductal carcinoma twice with two types of the antibody. Nine pathologists from 8 centers independently examined and scored all the 2 x 137 stained slides that were blinded for antibody type. Interobserver reliability was calculated using pair-wise kappa. Following discussion of the results, the Phase Two study was planned. Lab 2 and Lab 3 independently performed the HER2 staining according to the protocol for 60 invasive breast carcinoma cases. The same group of pathologists scored 2 x 60 stained slides that were masked for laboratories. Interobserver reliability and interlaboratory agreement from each pathologist were calculated using kappa statistics. Three interpreted categories--namely negative, equivocal and positive tests were used in the analyses. RESULTS: Phase One study showed interobserver agreement between pairs varied from kappa 0.75 (95%CI, 0.68-0.82) to 0.06 (95%CI, 0-0.14) while Phase Two study obtained pair-wise kappa scores ranged from 0.84 (95%CI, 0. 80-0.89) to 0. 65 (95%CI, 0.59-0.71). Interlaboratory kappa for each pathologist was 0.67 (95%CI, 0.61-0.73). CONCLUSION: The standardization of HER2 immunohistochemical assay was achieved through this two-phase study model. It had added benefits of improving pathologists' expertise and verifying the HER2 testing protocol to be used in Thailand.