"I have recently been diagnosed with a rare type of cancer and am currently undergoing treatment, including surgery and chemotherapy," Arnold said in a statement.
Arnold added that her prognosis is good. "While there is never a good time to get news like this, getting it just as we are building our new family is tough in many ways," her statement continued. "But being surrounded by the love of my husband and our two beautiful children is actually in many ways giving me the strength to fight it even stronger."
Arnold, 39, and her husband Bill Klein are parents to Will, 3, and Zoey, 2, whom they only recently adopted from India. The family became reality stars after a special about their wedding, The Little Couple: Just Married, became a hit in 2009.