US researchers found that current cannabis users had a 70 per cent raised risk of testicular germ cell tumour.
Most of the association appeared to be because of a more than doubled risk of developing a nonseminoma or mixed histology tumour.
Dr Janet Daling and her colleagues from the University of Washington conducted interviews on cannabis use with 369 men aged 18 to 44 diagnosed with a testicular germ cell tumour.
They compared the men's answers with those from interviews with 979 age-matched controls.
The researchers said the results were 'the first inkling' that cannabis use may be associated with testicular cancer.
Dr Daling and her team will now examine how cannabis might act on cannabinoid receptors to increase tumour risk.
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