The identification of tumor emboli in lymphatics is an adverse prognostic indicator for a woman with breast carcinoma. Rosen used criteria to positively diagnose lymphatic spread and to distinguish it from artifacts.
Criteria for lymphatic tumor emboli include:
(1) evaluation is limited to tissue peripheral to the carcinoma (beyond the margin of the invasive carcinoma)
(2) tumor emboli do not conform exactly to the space in which they lie
(3) endothelial cell nuclei should be present, with protrusion into the lymphatic space
(4) coexistent blood vessels
where:
• The usual location for finding convincing lymphatic involvement is 1 or more high power microscopic fields away from the advancing edge of the tumor.
• In retraction (shrinkage) artifact the tumor nests retain the exact contour of the surrounding stroma.
• Stromal cells can mimic endothelial cells. These tend to be slender nuclei that do not protrude into the clear space.
• Larger lymphatic channels tend to be adjacent to blood vessels.
• Lymphatic invasion can be diagnosed in the absence of adjacent blood vessels if all of the other findings are present.
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