Cancer progresses differently depending on ethnicity and sex. As does treatment and likelihood of receiving treatment at early stages.

Black women experience worse outcomes and are diagnosed with more severe forms of breast cancer than white women.

Cancer is not just one disease. Its progression will vary depending on type. If the AI is trained on only some strains of cancer, eg those traditionally found in white women in early detection scenarios, it might not generalize to other cancer types.

So yes, to your genuine question, medical imaging of cancer can vary depending on ethnicity because different cancers can vary between genetic backgrounds. Ideally there would be sufficient training data across the populations, but there isn't because of historical race bias. (Among other reasons.)