"In the last few weeks Johan Cruyff has undergone medical tests at a Barcelona hospital. He has been diagnosed with lung cancer," Carol Thate said in a statement.
"To respect Johan and his family's privacy and because tests have not been finalised, no further information will be given at this stage," Thate added.
"More will be given once these examinations have been finished," Thate said.
Cruyff, 68, who captained the Netherlands to the World Cup final in 1974 and who was one of the proponents of the "total football" philosophy, has been in-and-out of hospital over the last few weeks with health complaints.
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He won the prestigious Ballon d'Or award three times, a record shared with current UEFA chief Michel Platini and former Dutch striker Marco van Basten.
Afterwards, he enjoyed a hugely successful managerial career with Amsterdam-based Ajax and Catalan giants Barcelona as well as a brief spell as adviser to Club Deportivo Guadalajara in Mexico.
Cruyff still lives in Barcelona.
Often seen sporting a cigarette from the side of his mouth and known in his player days to light up at half time or just out of the showers -- Cruyff quit smoking after undergoing a double heart bypass operation in 1991.
He later appeared in an advertisement for the Catalan health department in which he was seen juggling a cigarette packet 16 times before booting it into touch.
"Football has given me everything in life," Cruyff says in the advert, which can still be seen on the YouTube video channel. "Tobacco almost took it all away.