Khan had tweeted on March 6 that he was suffering from a "rare disease," but did not say what it was.

On March 16, he revealed on Twitter that he has been diagnosed with a neuroendocrine tumour, addressing speculation by fans and the media over his health.

However, he didn't reveal whether the tumour was cancerous.

"Learning that I have been diagnosed with neuroendocrine tumour as of now has admittedly been difficult, but the love and strength of those around me and that I found within me has brought me to a place of hope," Khan said on Twitter.

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According to health experts, Neuroendocrine tumours can develop in different organs in the body and can be cancerous or non-cancerous.

Some neuroendocrine tumours can be treated with surgery or chemotherapy.

The 51-year-old actor has featured in several Hollywood and Bollywood movies including,"Maqbool," "Haasil," "Paan Singh Tomar," “Slumdog Millionaire”, “The Amazing Spider-Man” and “Life of Pi.”

One of India's best international acts, Khan won India's National Film Award in 2013 for his leading role in "Paan Singh Tomar," a biopic about a top athlete who becomes a bandit.

He was scheduled to kick off work on a film by Bollywood director Vishal Bharadwaj, but production was postponed due to Khan's illness.