Dermatologists say new research shows almost half of all melanoma deaths are from lumps that look like innocent pimples, rather than skin cancer.

Australia has the highest rate of melanoma in the world and dermatologists say the lesions, which do not present as typical skin cancers, grow at four times the rate of other melanomas.

The research published in the Australasian Journal of Dermatology found dermatologists were more accurate in identifying types of cancers than non-dermatologists.

Associate Professor John Kelly from the Victorian Melanoma Service says many doctors are dismissing the lumps, which are round and red or brown but which are in fact melanomas.

If nodules stay the same shape and size for a while, they are most likely harmless. If the lump comes up quickly, it is probably inflammatory like a pimple.

But Assoc Prof Kelly says if the red nodules are firm and growing progressively for more than a month, they should be checked as a nodular melanoma.

The most common melanomas look like an ugly mole and change in shape and colour.

Associate Professor Kelly said to bring down the death rate, doctors and patients need to be more aware of the spots, which grow quickly and can be easily mistaken for moles or pimples.

He said the nodular melanomas account for 15 per cent of melanomas, but almost 50 per cent of deaths.

"Lack of pigmentation is a key reason for failure to recognise these unusual presentations as melanoma," he said.

He says another reason for the high death rate is that the spots tend to grow very rapidly.

"Nodular melanoma grows in depth at four times the rate of other melanomas," he said.

One of the important features of these spots is that they change at a rate which is detectable over months.

"If we are to succeed in further reducing rates of death from melanoma, we must promote awareness amongst health care practitioners of this unusual presentation," Associate Professor Kelly said.

In 2014, about 14,240 Australians - 8,540 men and 5,700 women - are expected to be diagnosed with melanoma of the skin.

Why can skin cancers occur in parts of your body not exposed to the sun? ABC Health and Wellbeing's Cathy Johnson answers your questions

Melanoma is the least common type of skin cancer, but the fourth most common cancer in Australia.

It is the most dangerous form of skin cancer and is the seventh most common cause of cancer death in Australia.

People with fair skin are also at higher risk and the risk of melanoma increases with age.

In 2020, an estimated 17,570 Australians are expected to be diagnosed with melanomas of the skin.

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