Scientists believe they have developed a screening technique for members of families suffering from types of hereditary cancers.

The Imperial Cancer Research Fund says investigations of skin lesions may allow doctors to identify people likely to suffer from a group of cancers, particularly those of the colon.

By looking at skin warts, benign growths and malignant skin tumours in members of families with a history of HNPCC - hereditary non-polyposis colorectal cancer syndrome - it may be possible to identify people at high risk.

HNPCC has been linked to a defect in the repair mechanism for cells. Cells should replicate their DNA when they divide but if they do not they can cause alterations to microsatellites - the short repetitive sequences of genetic code contained in DNA.

This phenomenon, known as microsatellite instability (MSI), can cause tumours to develop.

Skin lesions

"We wanted to see if MSI is also present in skin lesions in patients belonging to HNPCC families," said Dr Veronique Bataille, of the Imperial Cancer Research Fund's Skin Tumour Laboratory.

"We discovered the presence of MSI in different types of benign skin lesions in these families, so the skin appears to be a marker of the genetic faults that may increase the risk of developing internal tumours."

Dr Bataille and her team inspected skin lesions of families with and without a history of hereditary colon cancer. In those with no family history, MSI was not found to be present.

"Detecting MSI in the skin could potentially be used in clinical practice to screen individuals in families at risk," said Dr Bataille.

There are about 3,000 HNPCC sufferers in the UK and of those, about 30% are also susceptible to other types of tumours, particularly those of the womb and the ovary.

Professor Soren Bentzen of the Gray Laboratory Cancer Research Trust at Mount Vernon Hospital, Middlesex, who has carried out studies of HNPCC in Denmark, said the screening proposal was "intriguing".

Discovering patterns for the colorectal cancer has proved difficult because of its sporadic occurrence, he said.

"You still need to base a screening strategy on some kind of family history because HNPCC is such a rare condition," he said. "But I can see why members of families where there is a high risk might want to have the test done."