Tombides, who has been battling testicular cancer since being diagnosed last July, has now been told he needs an urgent operation to remove cancerous tumours.
The 17-year-old was diagnosed while away on international duty with Australia at the FIFA U-17 World Cup in Mexico, and has been undergoing chemotherapy at London's St Bartholomew's Hospital since.
He now needs an operation to remove cancerous cells in his lymph glands next week, reported the Mail Online.
Senior West Ham players, led by skipper Kevin Nolan, asked Hammers boss Sam Allardyce to be allowed to make the public show of support before the home Championship match with Nottingham Forest this weekend.
Tombides has also receieved support from ex-Socceroo Craig Moore, who was himself diagnosed with testicular cancer two and a half years ago.
“I spoke to Dylan not long after the diagnosis and my message was that he should stay extremely positive,” said Moore.
“The success rates in treating this form of the disease are very high and I’m fortunate that I have the all clear.
“It’s tough for a teenager to deal with this, but Dylan has plenty of support from family and friends and I will be among many people who’ll be there for him throughout this time.
“I’ve told him to keep his head up and not to get too frustrated about missing his pre-season with West Ham. He’s a quality player with a great attitude and he can overcome this challenge.”