Biopsy Outcomes in Screen Detected Microcalcifications
Gelareh Farshid, Thomas Sullivan, Peter Downey, Grantley Gill, Steve Pieterse. BreastScreen SA, Wayville, SA, Australia; SA Pathology, Adelaide, SA, Australia; University of Adelaide, Adelaide, SA, Australia
Background: The assessment of microcalcifications detected on screening mammograms has led to a substantial increase in the incidence of DCIS. At present DCIS comprises 1 in 5 screen detected malignancies. From a medical stance, the diagnosis of DCIS represents an important opportunity to prevent its progression to invasive cancer. However, to the extent that not all cases of DCIS will progress to invasive cancer in the woman's lifetime, some view the diagnosis of DCIS and its treatment as instances of over diagnosis and over treatment.
Recent genetic and transcriptomic studies of the various stages of breast cancer development have led to the emerging view that beast cancer evolves along two divergent molecular pathways and that these changes are evident early in the genesis of the disease, including its in situ phase.
We wished to evaluate the histologic features of malignancies diagnosed as a result of assessment of microcalcifications in the setting of population based breast cancer screening.
Design: Between Jan 1992–Dec 2007 cases biopsied in which microcalcifications where the only imaging abnormality were included. Patient demographics, imaging features and final histology were subjected to statistical analysis.
Results: Of 2545 lesions assessed, 1220 (47.9%) were malignant (809 DCIS only, 411 DCIS with invasive cancer) and 1325 (52.1%) were non-malignant, including 122 (4.8%) pre-malignant lesions (LCIS, ALH and ADH). The DCIS grade was high in 58.5%, intermediate in 9.5% and low in 30.9%. Special DCIS subtypes constituted 1.2% of cases. There was no correlation between the imaging and histologic grades.
The invasive cancers were graded I in 21.2%, II in 43.8%, III in 14.1% and undetermined due to small size in 18.7%. Nodal metastases were detected in 15.6% of invasive cancers.
On multivariate modelling imaging grade, mammographic extent >15mm, palpable mass and screening episode were independent predictors of malignancy. Radiologic grade had the largest effect with lesions of grade 4 and 5 being 2.2 and 3.3 times more likely to be malignant respectively than grade 3 lesions.
Conclusions: In addition to their strong association with DCIS, particularly of high grade, the assessment of appropriately selected screen detected microcalcifications enables detection of invasive breast cancers, including small invasive cancers. This is an important opportunity for altering the natural history of breast cancer and improving women's health outcomes.
Monday, March 19, 2012 1:00 PM
Platform Session: Section B, Monday Afternoon