Sir Richard Hadlee will undergo further surgery this week after secondary cancer was discovered in his liver.
His wife, Lady Dianne, said the medical advice was that the disease was in its early stages and was operable.
The original tumour was discovered when the former cricket all-rounder had a routine, three-year colonoscopy in May.
He had it removed, and has been receiving a chemotherapy course expected to last a few months.
Lady Dianne said: "As with the first statement released on this matter, we disclose these details solely in the interests of transparency, and to avoid speculation and gossip.
"We would again ask that people respect our request for privacy."
The Herald spoke to a colorectal surgeon who said the chances of a full recovery were high if:
1. The secondary cancer was detected early.
2. There were a relatively limited number of growths.
3. The strain of the disease was not overly aggressive.
After standard operations to treat bowel cancer, growths could recur in the liver, lungs or abdominal cavity.
Hadlee has previously been diagnosed with Wolff–Parkinson–White Syndrome, a disorder which caused his heart to beat irregularly and required surgery to fix.
The 67-year-old's cricketing greatness is easily defined. He secured a world record 431 test wickets by retirement, was the lynchpin in New Zealand's golden era of the 1980s and brandished a knighthood in his final test.
Few players in the sport's history have carried as much responsibility within an international team.
Hadlee's 17-year test career saw him become the world test wicket record holder against India at Bangalore in 1988. He overtook Sir Ian Botham's 373-wicket mark when Chris Kuggeleijn caught India's Arun Lal in the slips. Hadlee took a wicket with his final ball in a test against England at Edgbaston in 1990 with the scorecard listing him as "Sir Richard".
His bowling average of 22.29 from 86 tests is among the best in the game. That statistic was complemented by the all-rounder tag, courtesy of 3124 test runs at an average of 27.16.
He received the supreme Halberg award twice and was honoured as the sportsperson of the 1980s.
Hadlee shared his method for combating recognition and pressure to the Herald before the 2015 World Cup. He prescribed embracing any added attention as expectations mount.
"[It's] a huge compliment to what you do on the field but it also carries responsibility when you're in the public domain."
Conversely, Hadlee said privacy was warranted in your own house.
"You should be able to do your own thing without worrying about cameras out front Hollywood-style. You're normal people at the end of the day, so still need to be left alone at times.
"However, when you're out on the road you are public property, so come to terms with it. You've got to be careful with your behaviour whether you're watching sport, at the movies, out fishing or at a restaurant."