Why to measure size of DCIS in specimen:
- Higher rates of invasive cancer detected according to DCIS size.
- Progression to invasive cancer occurred in 10% of DCIS patients with a DCIS tumor size between 2.5 to 3.5 cms, 57% for tumor size 3.6 to 4.5 cms and 71% for tumors between 4.5 and 6 cms.
- Tumors over 2.5 cms have a higher risk of progressing to invasive cancers.
J Exp Clin Cancer Res. 2006 Jun;25(2):223-7.
There are multiple methods for estimating the extent of DCIS (see Figure):
- DCIS in 1 block: The area involved by DCIS can be measured from a single slide, if DCIS is present in only 1 block. If separate foci are present, the largest distance between foci should be reported. This method will underestimate the extent of DCIS when multiple blocks are involved and should not be used in such cases.
- Serial sequential sampling: The entire specimen is blocked out in such a way that the location of each block can be determined. The extent of the DCIS can be calculated by using a diagram of the specimen, the thickness of the slices, and the location of the involved blocks.7-9 This method is recommended for all excisions likely to harbor DCIS or with previously diagnosed DCIS (eg, by diagnosis on a prior core needle biopsy).
- Nonsequential sampling: The number of blocks involved by DCIS is correlated with the extent of DCIS up to 40 mm.8 Multiplying the number of blocks involved by DCIS by the approximate width of a tissue section gives an estimate of the extent. In 2 studies, multiplying by 3 mm underestimated the extent of DCIS, and multiplying by 5 mm may overestimate the extent.8,9 Therefore, multiplying by 4 mm is recommended unless there is additional information that a different number would yield a more accurate result. This method may underestimate extent if not all areas of DCIS are sampled. Therefore, it is recommended that all tissue likely to be involved by DCIS be sampled (eg, all grossly abnormal tissue and all tissue with radiologically suspicious calcifications). When feasible, the entire specimen should be examined microscopically.
- This method may result in a larger estimation of extent than the serial sequential sampling method when DCIS is present in a large volume of tissue in 3 dimensions rather than in a predominantly linear distribution. The best estimate for correlation with outcomes (eg, residual disease or recurrence) will require further studies.
- This method can be applied to any specimen and will give a better estimation of extent than measuring extent on a single slide when multiple blocks contain DCIS.
- • Margins: If DCIS involves or is close to 2 opposing margins, the distance between the margins can be used as the extent of the DCIS within the specimen.
- • Gross lesions: In some cases of high-grade DCIS, there may be a gross lesion that can be measured. Confirmation of the gross size must be confirmed by microscopic evaluation.
- The largest estimate obtained using any of these methods should be used to report the estimated size (extent) of the DCIS.
