CHICAGO, Oct 13 (Reuters) - A study of nearly 40,000 women has found no overall link between caffeine and breast cancer, though some women who have benign breast lumps might be at a higher risk, researcher said on Monday.

A few earlier studies had suggested caffeine could play a role in breast cancer among those who consume what is probably the world's most widely used drug, Dr. Ken Ishitani of Boston's Brigham and Women's Hospital and Tokyo Women's Medical University and colleagues said.

But their look at 38,432 American women who were studied over several years starting in 1992 found "no overall association between caffeine consumption and breast cancer risk," they said in a report published in the Archives of Internal Medicine.

However, in women with benign breast disease -- nonmalignant lumps or tumors -- there was a significantly increased risk of breast cancer among those who drank four or more cups of coffee daily, the research team said. They said benign breast disease in general is considered a risk for breast cancer.

"These findings suggest high caffeine consumption may promote progression from pre-malignant breast lesions to breast cancers because most types of invasive breast cancer are thought to arise from certain pre-malignant lesions ... ," they said.

But there was no association in that group among those who drank fewer than four cups of coffee daily.

The findings involving those with benign breast disease are borderline, could be due to chance and warrant more study, the researchers said.

Caffeine is found not only in coffee and tea but also in chocolate and some medications. How the drug might influence cancer development in the breast is unclear, the authors said. (Reporting by Michael Conlon; Editing by Andrew Stern and Xavier Briand)

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