Breast cancer and pre-existing condition ?

My wife needed a tb test prior to entering nursing school. Since she is tests possitive, she needed a chest x-ray, which revealed a small nodule in one of her breasts. Her physician told he to get it checked out.

If, God forbid, it turns out to be cancerous, would it be excluded as a pre-existing condition since the nodule was discovbered prior to coverage, or would it be included in coverage since the diagnosis came after the coverage began?