I've been researching this topic for the past year and the most comprehensive and informative forum on IBC can be found here:
https://community.breastcancer.org/forum/81
Take your time and read through the various threads and you'll find answers to most of your questions. Be sure to sign up at the site and you can set email alerts for the topics that interest you.
Here's some reading as well.
Controversy: Terminology of multifocal or multicentric cancer: Some authors refer to the terms multifocal breast cancer and multicentric breast cancer, though the AJCC does not refer to either term and instead uses the term “multiple carcinomas”. These terms have not been used uniformly by various authors and some have even interchanged them. Traditionally, the distinction between multifocal and multicentric breast cancer is based on anatomic distribution of the tumor relative to a breast quadrant. Tumors within a single quadrant are multifocal whereas tumors involving several quadrants are multicentric (Jain S et al. Pathology 2009; 41: 57-67). Multifocal breast cancers are defined as being no more than 5 cm apart from each other in the same quadrant. Multicentric breast cancers are defined as being in different quadrants or as being in the same quadrant but more than 5 cm apart from each other. These definitions rely upon careful dissection of the specimens to exclude microscopic cancer connecting the foci and detailed measurements; this is perhaps why there is variation in the application of this terminology. Whether there is a biological basis for distinguishes multifocal and multicentric breast cancer is suggested by some early studies but remains to be fully elucidated. Various types of clonality studies suggest that multifocal tumors are clonally related in contrast to multicentric tumors, though these studies are small in number (Jain S et al. Pathology 2009; 41: 57-67). As mentioned above, there is controversy regarding the clinical significance of multiple synchronous carcinomas and more studies are needed. In the meantime, we follow suit of AJCC and use the term “multiple cancers” rather than multifocal or multicentric cancer.
Definition of inflammatory carcinoma and pT: AJCC defines inflammatory carcinoma as a clinical entity. Staging as pT4d requires these clinical features to be present: diffuse erythema and edema involving a third or more of the skin of the breast. Microscopically, dermal lymphatic invasion is typically seen in this setting, however dermal lymphatic invasion alone is NOT sufficient (nor necessary) to diagnose inflammatory carcinoma or stage pT4d. The clinical features must be present; if they are present but involve less than a third of the breast, AJCC states this should be staged as pT4b, not pT4d. Carcinoma that ulcerates the skin is staged as pT4b. If the clinical features are present but dermal lymphatic invasion is not, the patient may still be classified as inflammatory carcinoma and asT4d (though obviously this requires detailed information from the clinician). The detailed distinction between the T4 subcategories is based on outcome data justifying strict criteria for defining a patient as T4d.
Recommendation: Detailed clinical information is not always given to pathologists. We never use the term “inflammatory carcinoma” as a diagnostic line. Instead, “invasive ductal carcinoma with extensive dermal lymphatic invasion” is a more precise diagnostic line. If we see dermal lymphatic invasion but are not given any clinical information details, we provide the AJCC pT stage based solely on the pathologic findings (i.e. not pT4d) and then comment that if the appropriate clinical findings are present, stage pT4d should be considered. This transfers the determination of the final stage back to the surgeon, who has the first hand data that is required.
http://labmed.ucsf.edu/uploads/210/101_new_ajcc_staging_of_breast_cancer_what_has_changed.pdf
Good luck, there's lots of us out there. PM me if you wish.
