Vanessa Trump is sharing a concerning health update … she says she’s recently been diagnosed with breast cancer.

Vanessa made the announcement Wednesday in an Instagram post … revealing she’s already had a surgical procedure performed.

She says she’s working on a treatment plan with her medical team and is “staying focused and hopeful.”

Vanessa, the ex-wife of Donald Trump Jr., is dating Tiger Woods … and she says she’s “surrounded by the love and support of my family, my kids, and those closest to me.”

Unclear when Vanessa was diagnosed and what stage the breast cancer had reached.