A multicenter study of interobserver variability in pathologic diagnosis of papillary breast lesions on core needle biopsy with WHO classification

Abstract

Background: Papillary breast lesions (PBLs) comprise diverse entities from benign and atypical lesions to malignant tumors. Although PBLs are characterized by a papillary growth pattern, it is challenging to achieve high diagnostic accuracy and reproducibility. Thus, we investigated the diagnostic reproducibility of PBLs in core needle biopsy (CNB) specimens with World Health Organization (WHO) classification. Methods: Diagnostic reproducibility was assessed using interobserver variability (kappa value, κ) and agreement rate in the pathologic diagnosis of 60 PBL cases on CNB among 20 breast pathologists affiliated with 20 medical institutions in Korea. This analysis was performed using hematoxylin and eosin (H&E) staining and immunohistochemical (IHC) staining for cytokeratin 5 (CK5) and p63. The pathologic diagnosis of PBLs was based on WHO classification, which was used to establish simple classifications (4-tier, 3-tier, and 2-tier). Results: On WHO classification, H&E staining exhibited 'fair agreement' (κ = 0.21) with a 47.0% agreement rate. Simple classifications presented improvement in interobserver variability and agreement rate. IHC staining increased the kappa value and agreement rate in all the classifications. Despite IHC staining, the encapsulated/solid papillary carcinoma (EPC/SPC) subgroup (κ = 0.16) exhibited lower agreement compared to the non-EPC/SPC subgroup (κ = 0.35) with WHO classification, which was similar to the results of any other classification systems. Conclusions: Although the use of IHC staining for CK5 and p63 increased the diagnostic agreement of PBLs in CNB specimens, WHO classification exhibited a higher discordance rate compared to any other classifications. Therefore, this result warrants further intensive consensus studies to improve the diagnostic reproducibility of PBLs with WHO classification.

Encapsulated papillary carcinoma of the breast: A single institution experience

“…However, differentiating EPC from other papillary breast lesions is difficult when using preoperative core needle biopsies and having to rely on surgical excision to obtain accurate pathological diagnoses ( 10 ). Moreover, it has been suggested that pathologists are often confused regarding the displaced fragments of tumor tissue outside the fibrous capsule and true invasion ( 29 ). Additionally, a newly proposed variant of invasive lobular carcinoma may sometimes morphologically mimic EPC growth patterns ( 30 , 31 ).…”

Invasive papillary carcinoma of the breast

“…Papillary neoplasms of the breast comprise a broad range of proliferative diseases, including non-cancerous and abnormal growths, as well as malignant lesions. They constitute less than 3% of all breast lesions ( 1 , 2 ). According to the latest WHO classification of breast tumors (5th edition), papillary neoplasms of the breast include benign and malignant lesions ( Table 1 ) ( 3 ).…”