On my histopathology report under the diagnosis, it says "margins positive." what does that mean?

Margins: This means that the lesion is present at the edge of the tissue the surgeon removed, and therefore might not be completely removed. If this is a cancer, then you would want negative margins. If this is a benign lesion, then it doesn't really matter. A positive margin in cancer can be treated either with more surgery, or possibly with radiation, it depends on type of cancer and location, etc.