Margins of excision

Margins of excision are the boundaries of tissue removed during surgery, examined to determine whether a lesion or tumor reaches the cut edge and may remain in the body.

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Surgical margin: The cut surface or boundary of tissue removed in an operation, assessed for disease at its edge. This is the operative boundary whose clearance is reported as a margin of excision.
Re-excision: A second operation to remove additional tissue after an initial excision leaves suspected or confirmed disease behind. A positive margin may lead surgeons to remove more tissue.
Negative margin: A surgical margin with no tumor identified at the examined cut surface. It contrasts with tumor extending to the boundary, though definitions vary by tumor type.
Sampling error: The difference between a sampled portion of material and the full material it represents. Routine sections cannot show every point along a complex specimen boundary.
Histopathology: The study of diseased tissue under a microscope to diagnose and characterize disease. Microscopic examination distinguishes tumor at the cut edge from tumor merely near it.
Breast-conserving surgery: Surgery that removes a breast cancer with a surrounding rim of tissue while preserving most of the breast. Margin status commonly guides whether additional breast tissue must be removed.
Positive margin: A surgical margin where tumor is identified at the cut surface of the removed specimen. It indicates tumor reaches the excision boundary and may signal residual disease.
Specimen orientation: The marking and documentation of a removed tissue specimen’s anatomical directions and surfaces. Accurate orientation helps locate an involved margin for targeted further surgery.
Ink (pathology): Colored dye applied to a tissue specimen’s surface to mark its surgical boundaries for microscopic examination. Ink identifies the specimen’s true outer surface when sections are viewed under a microscope.
Mohs surgery: A skin-cancer operation that examines nearly the entire peripheral and deep surgical margin in stages. Its staged microscopic mapping allows tissue removal to stop once margins are clear.