DCIS Size / Extent Calculator
Four distinct CAP estimation methods; automatically reports the largest applicable estimate.
Free with an accountLog in to calculate. You can explore the inputs and reference material below; results need a free student account.
Educational and documentation-support tool based on the CAP DCIS protocol. Verify all values against the current version of the protocol and your institutional practice. Does not replace pathologic assessment.
Reference
About DCIS size / extent
The CAP DCIS protocol describes distinct methods for estimating the extent of ductal carcinoma in situ. Each method is calculated separately; the largest estimate obtained using any of the applicable methods is the value reported as the estimated size/extent of DCIS. Estimates are never averaged, added, or chosen by convenience.
Measured vs. estimated: a directly measured microscopic or gross dimension is a measured size. A value derived from block counts, specimen mapping, or margin distances is an estimated extent, and is never presented as an exact microscopic measurement.
Estimation methods
| Method | When used | Calculation |
|---|---|---|
| A · DCIS in one block | DCIS present in only one tissue block | Largest dimension in the slide/block. Separate foci: largest distance spanned by the foci (furthest edge − nearest edge) — focus sizes are never added. May underestimate when multiple blocks are involved. |
| B · Serial sequential sampling | Specimen sequentially sectioned in its entirety; block locations known | (last involved block − first involved block + 1) × section thickness. A directly measured microscopic extent, if larger, is used instead. |
| C · Nonsequential sampling | Number of involved blocks known, positions unknown | Blocks containing DCIS × tissue thickness (default 0.4 cm). May significantly over- or underestimate; not the sole method when a more accurate one is available. |
| D · Opposing margins / edges | DCIS involving or close to two opposing margins or edges | Distance between the two opposing margins. |
| Gross lesion (optional) | Grossly measurable lesion | Largest gross linear dimension — must be confirmed by microscopic evaluation; not automatically the DCIS size. |
Serial sequential sampling
Serial sequential sampling allows the extent to be calculated from a diagram of the specimen, the thickness of sections, and the location of the involved blocks. The 0.4 cm-per-block shortcut belongs to the nonsequential method and is not applied here — the calculation uses the span from the first to the last involved block. Enter the actual validated section thickness for the specimen.
Reference
College of American Pathologists (CAP). Protocol for the Examination of Resection Specimens from Patients with Ductal Carcinoma In Situ of the Breast.