Punchy biopsy needs more investigation, what does this mean?

My husband had a suspicious mole removed via the "punch" technique 2 weeks ago and was told he would be contacted with the results. 
Today he had a phone call, he was told the biopsy needed further investigation and he would have to wait a further 2 weeks for results. 
He asked if its anything sinister as understandable having to wait again is causing a lot of anxiety and stress but the lady was only passing on the message and couldn't comment any further or give any further information .

what could this mean if it requires further investigation, is there anyone we can go to for more information?