A Panel of Cytokeratin (CK) 5/6, p63 and Smooth Muscle Myosin (SMMS) Immunostain Improves Diagnostic Accuracy of Papillary Lesions of the Breast Diagnosed on Core Needle Biopsy (CNB)
Shivani Kandukuri, Kristine Astvatsaturyan, Shikha Bose. Cedars-Sinai Medical Center, Los Angeles, CA
Background: Histopathologic evaluation of papillary lesions (PL) of the breast on CNB is challenging with greater than 20% rate of under diagnosis of atypia or malignancy. Thus complete excision is the standard of care. An accurate core biopsy diagnosis of the final pathology would allow appropriate management of patients. Various immunostains are being tested as surrogate markers to improve diagnostic concordance. Our study evaluates the diagnostic accuracy of a panel of three immunostains in PL of the breast.
Design: From 1998 to 2011, all departmental cases diagnosed as PL of the breast on CNB with follow up excisions were reviewed. CNB's containing only pure papillary lesions were included. Immunostaining (IHC) was performed using a dual cocktail of p63 (brown nuclear reaction product) and SMMS (red cytoplasmic stain) and CK5/6 on consecutive sections of selected blocks. IHC were evaluated without knowledge of original and final diagnoses. PLs showing uniform, diffuse positivity with all three markers were diagnosed as benign; those with diffuse negative staining were diagnosed as malignant while those showing patchy staining with focal areas of negativity were diagnosed as atypical.
Results: The study included 34 cases, 11 of which were benign, 4 atypical and 19 malignant on excision. The original CNB diagnoses were benign in 19, atypical in 9 and malignant in 6. Four of the malignant cases were interpreted as benign and 9 as atypical on CNB. Additionally the 4 cases with atypical final diagnosis were interpreted as benign on CNB. Concordance was observed in 17 of 34 cases (50%). After IHC, the predicted diagnoses were 15 benign, 9 atypical and 10 malignant. The remaining 9 cases with malignant final diagnosis were diagnosed as atypical (n=8) and benign (n=1). The four atypical cases were interpreted as atypical (n=1) and benign (n=3). The overall concordance after immunostaining improved to 65%. Of the 19 malignant PL, 10 were diagnosed as malignant after IHC and 8 as atypical. There was one false negative case.
Conclusions: - Immunostaining of CNB of breast with PLs improves concordance with excision diagnosis.
- PL diagnosed as atypical after IHC require excision.
- PL diagnosed as benign after IHC may be followed up after careful consideration of clinical features.
Wednesday, March 21, 2012 1:00 PM
Poster Session VI # 21, Wednesday Afternoon