A new report suggests that the continued use of the beneficial drug, tamoxifen, can cause a rare but dangerous side effect increasing the chances of an uncommon tumor.

Previous studies have shown enough proof that tamoxifen not only prevents the spread of breast cancer but also reduces the recurrence.

The author of the report has clearly stated that this study should not hamper the medical practice of this drug because this report is based only on observational study and not on controlled clinical trials considered the gold standard in medicine.

"All treatments have risks associated with them," said Dr. Christopher I. Li, an associate member of the Fred Hutchinson Cancer Research Center in Seattle and the first author of the study, which appeared Tuesday in Cancer Research. "Here we're adding another potential risk to the risk side of the equation for tamoxifen. But the broader context is that tamoxifen lowers a patient's risk of dying of the disease."

A new study suggested that women who used tamoxifen were 60 percent less likely to develop cancer or any rare tumor growth in the second breast than non users.

The study also found that tamoxefin users were four times more likely to develop a new tumor which was not estrogen-sensitive. Although these tumors are hard to treat the occurrence is rare.

The major concern related to the release of this report is that the breast cancer patients who are already taking tamoxefin might stop taking it but they have to understand that they already are suffering from this disease and are taking the drug to prevent further spread.