[179] Core Biopsy Diagnosis vs. Excision Diagnosis of Papillary Lesions of the Breast: The Impact of Breast Pathology Subspecialization.

Kiran Jakate, Marina Debrot, Frances P O'Malley, Anna Marie Mulligan. University of Toronto, ON, Canada; St. Michael's Hospital, Toronto, Canada

Background: Classifying papillary lesions of the breast on core biopsy (CB) can be challenging. The extent to which subspecialty training in breast pathology might mitigate such difficulties has not yet been reported. We investigated change in diagnoses upon surgical excision according to subspecialist training in breast pathology as well as interobserver agreement between specialized breast (BP) and non-breast pathologists (NBP) in classifying these lesions.
Design: CB of 259 papillary lesions from 245 patients diagnosed between 2000-2010 were classified by both a BP and NBP into benign, atypical, DCIS/encapsulated papillary carcinoma (EPC) or invasive. Rates of change in diagnostic category in the surgical excision specimen were calculated for BP and NBP. Comparisons were performed using Χ² test. Kappa values were calculated for interobserver agreement.
Results: Of 156 lesions with subsequent excision, 81 were originally diagnosed as benign, 39 atypical, 26 DCIS/EPC and 10 invasive on CB. There was no significant difference between BP and NBP in the rate of upgrade from benign to atypical/malignant diagnoses; although, downgrades from atypical/malignant to benign were more commonly seen for NBP (P=0.002)(Table 1). Overall, the BP CB diagnosis was less likely to differ from the excision diagnosis (P=0.0001).

Table 1

Change in Diagnosis	NBP N(%)	BP N(%)	P-value
Benign to atypical	10(6.4)	11(7.1)	1.0
Benign to malignant	14(9)	6(3.8)	.11
Atypical to malignant	23(15)	17(11)	.40
Atypical to benign	10(6.4)	2(1.3)	.04
Malignant to benign	5(3.2)	0	.07
Other	19(12)	13(8.3)	.35
No change	75(48)	107(69)	.0001

NBP=non-breast pathologist, BP=breast pathologist; Total N=156

There was no difference in radiologic size of the lesion or number of cores between benign papillomas which were upgraded and those that were not. No benign lesions were upgraded to malignant if radiologic-pathologic concordance was seen. Interobserver agreement between BP and NBP diagnoses was in the 'fair agreement' range (Κ=0.39) with perfect agreement in 66.4% of cases.
Conclusions: Correlation between CB and excision diagnoses for breast papillary lesions is significantly greater for BP than NBP. This is largely due to a tendency to overcall atypia or malignancy on CB by NBP. Upgrades from benign to atypical or malignant did not significantly differ according to subspecialization and were not seen in a setting of radiology-pathology concordance, suggesting conservative management in these cases may be appropriate.
Category: Breast

Monday, February 28, 2011 9:30 AM

Poster Session I Stowell-Orbison/Surgical Pathology/Autopsy Awards Poster Session # 20, Monday Morning