How to treat patients who have microinvasive breast cancer - tumours that are 1 mm or less in size (the thickness of a dime) -- is somewhat controversial.

Can these tiny tumours affect the lymph nodes and spread cancer to other areas of the body?

Physicians at the Virginia Piper Cancer Institute wanted to know if surgical procedures to test the lymph nodes for cancer were always necessary.

They examined the outcomes of 294 patients who were treated between 2001 and 2015.

Only 1.5 percent had positive lymph nodes - indicating the rare possibility of metastatic cancer.

And the only patients with positive lymph nodes had microinvasive tumours that were associated with relatively large non-invasive tumours (ductal carcinoma in situ or DCIS).

"These findings allow surgeons to select which patients with microinvasive tumours may actually benefit from lymph node sampling, while sparing other patients from this procedure," said Tamera Lillemoe, M.D, pathologist and a study co-author.

Source: Allina Health