The guidelines allow medical specialists to identify which patients have more aggressive forms of breast cancer, which means they can be classified appropriately and their treatment can be tailored, according to a university statement.

The team which developed the guidelines specifically investigated metaplastic breast carcinomas (MBC), a rare but aggressive form of breast cancer, said the university's Amy McCart Reed.

"For patients with MBC, we found the number of different cell types in the tumors had a significant impact on survival," she said.

"The more diverse the tumor, the worse the patient's prognosis is likely to be.

"Among patients with a bad tumor type like MBC, there are some who will do well and some will do poorly, and this new metric helps us to categorize this."

The World Health Organization (WHO) will also incorporate the guidelines into the fifth edition of its major "Blue book" and "Classification of Tumours of the Breast" from next year, said the university.

"Previously, the WHO guidelines have described the types of cancer cells within tumors without telling pathologists specifically what and how much to record," said McCart Reed, whose team's study was reported in The Journal of Pathology medical publication.

"Now we can advise pathologists to record the number of types of morphologies within tumors because a more accurate prognosis can be made based on this."