How serious if my friends diagnosis of invasive carcinoma ductal with medullary carcinoma?

Not trivial!: Breast cancer, is most commonly of the invasive ductal type. Often there are mixed patterns with medullary or lobular histologies. Perhaps others as well. The most important factors however aren't mentioned here. Age, stage, grade, lymph node involvement all play a much more prognostic role at this point.

Extremely: Her chances for cure depend on how early it was found.