The 45-year-old had a cancerous tumour removed from his throat in November 2011 and in December 2012 he suffered a relapse and underwent surgery again followed by 10 weeks of chemotherapy and radiotherapy in New York.
He returned to the helm of Barcelona in March and led the club to the Spanish league title.
Barcelona president Sandro Rosell and the club’s sporting director Andoni Zubizarreta will give a press conference at 8:30 pm (1830 GMT), the club said on its website without giving further details.
But several Spanish media outlets said the club would announce that Vilanova has had a relapse and was leaving his post.
“The coach has recently undergone tests which confirmed the bad news,” the online edition of Catalan sports daily Mundo Deportivo said.
Top-selling daily El Pais said Vilanova’s latest tests “revealed complications of the disease”.
Vilanova replaced Pep Guardiola as manager in June 2012, having previously worked as his assistant.