[191] Diagnostic Utility of WT-1, Ki 67 and CD117 in Fibroepithelial Lesions of the Breast

D ElDemellawy. William Osler Health Center, Brampton, ON, Canada; Northern Ontario School of Medicine-, Thunder Bay, ON, Canada

Background: Definite diagnosis of fibroepithelial lesions (FEL) as fibroadenoma (FA) or benign phylloides tumor (BPT) in core needle biopsies (CB) is difficult in some cases. Although both tumors are benign discrimination between both tumors is crucial as FA is usually managed by follow up or simple enucleation in contrast to BPT which is managed by adequate excision. The latter requisites free margin of at least 1 cm. To the best of our knowledge no definite clinical or imaging parameter can discriminate accurately between the two tumors. Presently, molecular and immunohistochemical techniques play a limited role in the diagnosis of FEL.
Design: Forty five FEL diagnosed in CB were prospectively studied. None of these cases showed necrosis, prominent cellular pleomorphism, stromal overgrowth, brisk stromal mitotic activity, leaf like pattern, entrapped native epithelial or fibroadipose tissue or heterologous elements. Immunohistochemistry using WT-1, Ki 67 and CD117 were applied on CB. In each case pattern and intensity of staining and expressing cells were assessed. Finally subsequent excision was reviewed.
Results: All the forty five patients were female, with a mean age of 41 years. Each patient had a palpable mass or mammographic finding indistinguishable from FA. On imaging tumor size ranged from 5 mm to 28 cm. All cases were diagnosed on CB as benign FEL, with a comment favoured FA in forty cases. Subsequent excision revealed FA in twenty nine cases: ten were cellular; two were complex and seventeen were FA, NOS. The remaining sixteen cases showed phylloides tumor (PT), three of which were borderline and thirteen were benign. WT-1 immunohistochemical stain showed stromal cytoplasmic expression in the proliferating spindle cells in all cases of PT. Negative expression was noted in the native breast tissue. All the cases of FA were negative identical to the native breast tissue. Low Ki 67 proliferation index ranged from 0%-15% was noted in both FA and PT. No statistical significance was present between the two neoplasms. All the cases included in the current study were negative for CD117.
Conclusions: The current study shows that immunohistochemistry using WT-1 antibody applied on CB is useful tool that aids in further classification of difficult cases of FEL, and thus guide management of these cases, in contrast to CD117 and Ki 67 antibodies.
Category: Breast

Wednesday, March 24, 2010 9:30 AM

Poster Session V # 39, Wednesday Morning


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