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Mathew Knowles has been diagnosed with breast cancer.

Beyonce and Solange's dad is opening up about his personal battle for the first time -- he's planning to discuss it on 'GMA' Wednesday morning. It's unclear how recently Mathew was diagnosed.

While breast cancer in male patients is rare, some of the numbers are alarming ... especially for Mathew.

Less than 1 percent of all breast cancer cases involve men. However, it's most frequently diagnosed in men between the ages of 60 and 70. Mathew is 67 years old.

Also, the median age for black male patients with breast cancer is 63.

According to the National Breast Cancer Foundation, the mortality rate for men is higher than it is for female patients.

Mathew remarried Gena Avery in 2013. He's had 2 more children since he and Tina Knowles divorced.