Comparison of immunohistochemical staining in breast papillary neoplasms of cytokeratin 5/6 and p63 in core needle biopsies and surgical excisions

This study investigated the usefulness of immunohistochemical staining for cytokeratin (CK) 5/6 and p63 for the precise categorization of papillary lesions by core needle biopsy (CNB) through correlations of CNB and subsequent surgical excision results. We retrospectively reviewed 75 cases with both CNB and subsequent surgical excision showing papillary lesions on immunohistochemistry for CK5/6 and p63. Histologic and immunohistochemical criteria used to classify papillary lesions were applied equally to the CNB and surgical excision samples. Final diagnostic concordance with clinical significance was noted in 69 (92.0%) cases. Six cases had diagnostic discrepancies that changed from papilloma with atypical ductal hyperplasia (ADH) to papilloma in 1 case, from papilloma with ADH to papilloma with usual ductal hyperplasia in 3 cases, and from papilloma with ductal carcinoma in situ to papilloma with ADH in 2 cases. In conclusion, although the results of CK5/6 and p63 in CNBs of papillary neoplasms were mostly representative of the final results for CK5/6 and p63 in subsequent surgical excisions, excisional biopsy is required for definitive subtyping due to the heterogeneous nature of papillary lesions and the possibility of overdiagnosis of papilloma with ductal carcinoma in situ in CNB, resulting in unnecessary radiation and hormone therapy.