Mitotic Figure Counts Are Significantly Higher in Breast Cancer Tumorectomy Specimen Than to Needle Biopsies
Cornelia Schaper, Candice Rochat, Antoine Nobile, Ellen Obermann, Hans-Anton Lehr. Breast Center Südbaden, Freiburg, Germany; CHUV, Lausanne, Switzerland; University Hospital, Basel, Switzerland
Background: We tend to rather up- than down-grade breast cancers in tumorectomy specimen when compared to biopsy material and we had the vague impression that the effect is largely due to increased mitotic figure counts in tumorectomy specimen.
Design: We performed mitotic and apoptotic figure counts and immunohistochemical detection of cell cycle specific antigens (Ki-67, histone H3) in paired needle biopsy and tumorectomy specimen in two independent cohorts in Germany (n=170) and Switzerland (n=52). To exclude observer bias, counts were verified on virtual TMNs (blinded as to whether the scanned high power fields were from biopsies or from tumorectomies).
Results: The numbers of mitotic figures were significantly increased by a factor of 2.2 and 1.9 in the German and the Swiss cohorts, respectively. In contrast, the Ki-67 labeling index was comparable in biopsies and tumorectomy specimen in both cohorts. The spectrum of mitotic figues (from prophase to telophase) was significantly broader in biopsies than in tumorectomy specimen, where most mitotic figures were in pro-metaphase or in metaphase. The numbers of apoptotic figures were also increased in tumorectomy specimen when compared to biopsies.
Conclusions: We speculate that the increased numbers of mitotic figures in tumorectomy specimen reflects continued cell cycle progression into metaphase. Small biopsies are rapidly fixed (30min-1hr) while formalin only slowly penetrates larger tumorectomy specimen. As a consequence, biological processes, including passage through a committed cell cycle, may continue for quite some time in the tumorectomy specimen, resulting in higher numbers of mitotic figures.
Tuesday, March 20, 2012 9:30 AM
Poster Session III # 21, Tuesday Morning