Malignant Findings

Ductal Carcinoma In Situ

DCIS is confined to the breast ducts without invasion of the basement membrane and accounts for 25% to 33% of all screen-detected malignancies. The classic mammographic appearance of DCIS includes fine branching, heterogeneous, and/or pleomorphic calcifications in a grouped, segmental, or linear distribution, typically conforming to the path of the branching breast ducts. However, up to 20% of DCIS may also present as a focal mass with or without associated microcalcifications ( Figs. 9.1 and 9.2 ). Moreover, in cases of DCIS presenting primarily as microcalcifications, tomosynthesis may identify a subtle associated mass representing the invasive component otherwise occult on conventional 2D mammography alone. Occasionally DCIS may present as a subtle architectural distortion, which may only be seen on tomosynthesis ( Fig. 9.3 ).

Magnification views cannot be performed with tomosynthesis and in most cases of suspicious calcifications will still be required. However, some microcalcifications associated with DCIS may be better or equally well seen on tomosynthesis compared with 2D mammography. This is especially true if coarse and heterogeneous calcifications are predominately located within the same plane as the tomosynthesis slice ( Fig. 9.4 ). However, more often, microcalcifications are distributed beyond a single tomosynthesis slice, and it can be challenging to see the whole picture across the multiple slices. Out-of-plane coarse calcifications may also produce a distracting “ghosting” artifact on tomosynthesis. Finally, subtle and fine microcalcifications may be seen on 2D mammography alone and not seen at all on tomosynthesis. As a result, magnification views are still often helpful for complete evaluation to capture the entire group on a single 2D image and also to detect additional subtle calcifications not readily appreciated on the original 2D or tomosynthesis mammogram ( Fig. 9.5 ).

Some of the limitations of tomosynthesis in evaluation of microcalcifications can potentially be overcome by using the “slabbing” technique, in which the reconstructed slice thickness is increased using the tomosynthesis slider bar or by combining multiple tomosynthesis slices on the projection image ( Fig. 9.6 ). Synthesized tomosynthesis may allow for improved visualization of some malignant calcifications, although more studies are needed to determine the future utility of synthesized tomosynthesis images in lieu of 2D magnification. Currently, whether microcalcifications are clustered, segmental, or regionally distributed, magnification views are easy to obtain and can provide the diagnostic confidence required when searching for fine or subtle suspicious microcalcifications and determining the final Breast Imaging Reporting and Data System (BI-RADS) assessment.

Invasive Carcinoma