Tumor Size (Size of Invasive Carcinoma) in Breast Carcinoma

Breast Carcinoma reporting;

Tumor Size (Size of Invasive Carcinoma)

• The size of an invasive carcinoma is an important prognostic factor. 
• The single greatest dimension of the largest invasive carcinoma is used to determine T classification 
• The best size for AJCC T classification should use information from imaging, gross examination, and microscopic evaluation. 
• Visual determination of size is often unreliable, as carcinomas often blend into adjacent fibrous tissue. 
• The size by palpation of a hard mass correlates better with invasion of tumor cells into stroma with a desmoplastic response. 
• Sizes should be measured to the nearest millimeter. 
• In some cases, the size may be difficult to determine.

How to measure size of breast invasive carcinoma:

A. Invasive carcinoma with surrounding ductal carcinoma in situ (DCIS). The size only includes the area of the invasive carcinoma and does not include the adjacent DCIS. The size should be measured to the closest 1 mm.

Invasive carcinoma and DCIS: The size measurement includes only the largest area of contiguous invasion of stroma. Surrounding DCIS is not included in the size measurement.

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B. Small invasive carcinoma with prior core needle biopsy. The size of the carcinoma in the core needle biopsy should not be added to the size of the carcinoma in the excisional specimen, as this will generally overestimate the true size. The best size for classification must take into consideration the largest dimension of the carcinoma in both specimens as well as the size by imaging before the core needle biopsy.

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C. Small invasive carcinomas with adjacent biopsy site changes. In some excisional specimens, a small carcinoma will be present adjacent to a relatively large area of biopsy site changes. The actual size cannot be determined with certainty. The size in the core needle biopsy, in the excisional specimen, and by imaging should be considered to determine the best size for classification.

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D. Multiple invasive carcinomas. If multiple carcinomas are present, the size of the largest invasive carcinoma is used for T classification. The modifier “m” is used to indicate that multiple invasive carcinomas are present.

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E. Multiple invasive carcinomas in close proximity. It may be difficult to distinguish multiple adjacent carcinomas from one large invasive carcinoma. Careful examination of the specimen with submission of tissue between grossly evident carcinomas is essential. Correlation with imaging findings can be helpful. Generally, microscopic size confirmation of the largest grossly identified invasive carcinoma is used for T classification.

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F. Invasive carcinomas that have been transected. If an invasive carcinoma has been transected and is present in more than 1 tissue fragment, the sizes in each fragment should not be added together, as this may overestimate the true size. In many cases, correlation with the size on breast imaging will be helpful to choose the best size for classification. In other cases, the pathologist will need to use his or her judgment in assigning an AJCC T category.

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DCIS with microinvasion: 

• Microinvasion is defined by the AJCC as invasion measuring 1 mm or less in size. 
• If more than 1 focus of microinvasion is present, the number of foci present, an estimate of the number, or a note that the number of foci is too numerous to quantify should be reported.
•  In some cases, immunoperoxidase studies for myoepithelial cells may be helpful to document areas of invasion and the size of the invasive foci.
•  Invasive tumors that are larger than 1.0 mm but less than 2.0 mm are rounded up to 2.0 mm.