Can a radiologist tell if a nodule is cancer just by looking a on a digital mammogram?

"suggestive of": "consistent with" are terms used to describe findings on mammograms. The definite diagnosis is by biopsy.

No. Diagnostic: Radiologists specialize in mammo interpretation, but they describe findings, suggest more imaging, but the truth comes only after biopsy. Screening is done with x-rays that are not sensitive in many cases, diagnsotic procedures can be much more sensitive. False results, positives and negatives, plague x-ray mammograms.

Probability of Ca: Nodules are characterized on mammo by various features that increase or decrease the probability of cancer. In order to remain accredited to interpret mammo, radiologists are required to render a final interpretation categorizing the lesion into one of the following categories: benign, probably benign, suspicious, or highly suspicious. The last category implies at least a 95% chance of malignancy

Biopsy for diagnosis: A radiologist may suggest that a nodule has the characteristics of cancer, but definitive diagnosis requires biopsy or removal of the nodule and examination of the tissue by a pathologist.

Sometimes: There are some masses and calcifications that have a characteristic look to them that makes one "highly suspicious" of breast cancer. The only way to get a definitive answer is to have a biopsy-core needle or fine needle is preferred.

Probability of Ca: Nodules are characterized on mammo by various features that increase or decrease the probability of cancer. In order to remain accredited to interpret mammo, radiologists are required to render a final interpretation categorizing the lesion into one of the following categories: benign, probably benign, suspicious, or highly suspicious. The last category implies at least a 95% chance of malignancy