Inter-Observer Variability by Breast Pathologists in the Distinction between Fibroadenomas with Increased Stromal Cellularity and Phyllodes Tumors.
Thomas J Lawton, Geza Acs, Pedram Argani, Gelareh Farshid, Michael Gilcrease, Neal Goldstein, Frederick C Koerner, Jordi Rowe, Melinda Sanders, Carol Reynolds. Seattle Breast Pathology Consultants, WA
Background: Fibroepithelial lesions with cellular stroma are frequently termed “cellular fibroadenoma” and the criteria for distinguishing them from a phyllodes tumor are vague and subjective. However, the clinical implications and surgical management for these two lesions are usually different.
Design: We selected 21 cases of fibroepithelial lesions that were sent in consultation with the differential diagnosis of cellular fibroadenoma vs. phyllodes tumor. One to two representative slides of each case along with patient age were sent to 10 pathologists who specialize in breast pathology. Included with the cases were the WHO criteria for phyllodes tumors and a diagnosis form with an option of "other." For the purposes of data reporting, fibroadenoma and cellular fibroadenoma are considered similar.
Results: In only two cases was there uniform agreement as to whether the tumor represented a fibroadenoma or phyllodes tumor (one case each). However, in the phyllodes tumor case subclassification varied from benign to malignant. In nine cases, the diagnoses ranged from fibroadenoma to borderline phyllodes tumor. In four of these cases, more than one pathologist made the diagnosis of borderline phyllodes tumor. In four cases the diagnoses were split nearly equally (5/5 or 6/4) between fibroadenoma and benign phyllodes tumor. If the diagnoses of fibroadenoma/cellular fibroadenoma and benign phyllodes tumor were combined and separated from the borderline and malignant phyllodes tumors, there was 100% agreement in 52% of cases (11/21) and 90% agreement in 81% of cases (17/21).
Conclusions: The distinction between a cellular fibroadenoma and a phyllodes tumor can be subjective. Even pathologists who specialize in breast pathology disagree on this distinction in a significant proportion of cases, but the decision for further surgical treatment can rest on these subjective criteria. However, there is considerable agreement when cellular fibroadenomas and benign phyllodes tumors are distinguished from borderline and malignant phyllodes tumors. Further studies are needed to determine if there is a clinically significant difference between cellular fibroadenomas and benign phyllodes tumors for the subset of cases in which the distinction is subjective and apparently not reproducible.
Monday, February 28, 2011 1:00 PM
Poster Session II # 55, Monday Afternoon