Anne-Marie O’Shea

There is increased understanding of the heterogeneity of breast tumors, with greater emphasis now being placed on histological and molecular profiles and, in particular, their implications for prognosis and therapy. This review addresses breast cancers of unusual histological subtype with an approximate incidence ≤1%. Given the rarity of these tumors, the literature contains primarily case reports, small series, and population-based studies. Data are heterogeneous and almost entirely retrospective, frequently gathered over long time periods, in the context of changing pathological techniques and reporting. In addition, our understanding of the disease biology and therapeutic context has also evolved significantly over this time. There is often limited information about the specific therapies used and the rationale for choosing such an approach. Meaningful comparisons of treatment modalities are not feasible and it is not possible to define management guidelines. Instead, this review correlates the available information to give an impression of how each subgroup behaves-of the favored surgical technique, responses to therapy, and prognosis-as well as the emerging molecular data, highlighting new research areas for potential target in clinical trials. Each tumor subtype described represents a small but real cohort of patients with breast cancer, and although inferences may be made from this review, we are mindful of the paucity of data. The management of each patient must be considered in the context of their unique clinical presentation and correlated with the evidence-based principles that apply to more common breast cancer histologies.

O’Shea A-M, Rakha E A, Hodi Z, Ellis I O & Lee A H S(2011) Histopathology59, 543–548 Histological grade of invasive carcinoma of the breast assessed on needle core biopsy – modifications to mitotic count assessment to improve agreement with surgical specimens Aims: Histological grade assessed on core biopsy of mammary invasive carcinomas tends to underestimate the grade in the excision specimen. A major factor is underestimation of mitoses. The aim of this study was to improve the assessment of mitoses in core biopsies. Methods and results: In a test set (100 tumours), reducing the threshold for a mitotic score of 2 from 11 mitoses per 10 high-power fields (diameter 0.61 mm) to 6/10 resulted in improved agreement between core and excision from 69% to 73%. In tumours graded as T3 P3 M1 (few tubules, marked nuclear pleomorphism and few mitoses) on core (a group with poor agreement of grade between core and surgical specimens), this change in threshold also improved agreement in four tumours. Use of the mitotic count in the core of axillary nodal metastasis, if higher than the count in the breast core, improved agreement in two patients. Use of both approaches in a validation set (349 tumours) improved agreement from 65% to 70% in the whole group, and from 31% to 55% in tumours scored as T3 P3 M1 on the core. Conclusions: These strategies improve the accuracy of grading on core biopsy and are of particular value in T3 P3 M1 tumours.