Accurate staging of early breast cancer has become ever more important, especially with the current debate about when it is better to exclude adjuvant chemotherapy. Patients don’t like it and physicians are becoming more and more aware of the unjustified long term complications in patients who will not benefit from 6 months of chemo. Genetic profiling e.g. Oncotype DX is already being used to exclude chemotherapy in patients with cancers showing a favorable genetic profile.
Risk adaptive approaches to therapy have been in place ever since the TNM staging system was used to determine therapeutic options. The AJCC publishes very clear cut-offs for each stage (and substage) which can be measured by the pathologist / radiologist and estimated at the bedside. Although this may look straightforward. In practice, there is still a lot of confusion.
Take for example a patient presenting with intraductal papillary carcinoma with several foci of invasive ductal carcinoma. How do we measure the various components and how do we add them up?
Ductal carcinoma in situ (DCIS) is also known as intraductal carcinoma are non-invasive components (does not invade the basement membrane). It accounts for nearly 25% of all breast cancer diagnoses. These may be measured in the pathology report as a length of its greatest dimension but more commonly as a percentage the tumor mass. What is important here is whether the intraduct component of an excised mass is extensive or not. As this is an indicator of possible residual disease (disease extent may be larger than thought). Extensive is taken as more than 25% of the tumor is in the intraduct compartement. This is not a contraindication for breast conservation surgery (as long as the margins are negative) but requires reassessment for the presence of a residual, which is a reflection of the multifocality, and multicentricity associated with these tumors.1
The real challenge comes when measuring and adding up several foci of invasive breast cancer.
There are two terms here that need to be clearly defined: multicentric breast cancer and multifocal. Even though for the purpose of staging and measurement it would not make a difference, the difference has important therapeutic implications.
Multicentricity: means 2 / more invasive breast cancer foci in separate breast quadrants. It is an absolute contraindication to breast conservation surgery.
Multifocality: means 2 or more in invasive breast cancer foci in same quadrant. It is not a contraindication to conservative surgery.
So how do we add multiple foci in the breast to reach an overall T stage? One study published in 2005 in the JCO compared two methods: (1) largest tumor focus diameter and (2) the aggregate
diameters of all tumor foci and then correlated that with nodal stage. The study concluded that by failing to add all the foci the patients were understaged.2
Therefore, in a case of intraduct breast cancer with multiple foci (multicentric / multifocal) you want to add all the invasive foci together and if the sum is less than 2 cm then it’s still T1 and so on. You also want to look at whether the intraduct component is more than 25% (extensive) and in this case you may need to consult the surgeon about the need to reassess for the presence of a residual.
CITE THIS ARTICLE:
Tamer M. Fouad, M.D.. Measuring the primary tumor: intraductal breast cancer with foci of invasive ductal carcinoma. Doctors Lounge Website. Available at: https://www.doctorslounge.com/index.php/blogs/page/302. Accessed June 13 2021.
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