That happened with my husband. His first biopsy, by an oral surgeon, took only a tiny area of a leukoplakia (white patch) on his tongue, and the path report came back showing moderate dysplasia -- abnormal, but not cancer. The path report did warn about a possible "skip effect," meaning that there could be cancer in areas that were not biopsied -- so perhaps the pathologist saw something that raised a red flag but couldn't be stated definitively as cancer.
When my husband had the whole thing removed by an ENT a month later, that path report came back squamous cell carcinoma in situ (earliest stage).