Explainer: What is Sarcoma, Doc Willie Ong's rare cancer?

MANILA, Philippines — Cardiologist and content creator Dr. Willie Ong revealed earlier this week that he is battling "sarcoma cancer" in his stomach and currently undergoing treatment.

In a video message recorded from his hospital bed last month, Doc Willie said doctors detected a mass measuring 16 centimeters "deeply hidden" behind his heart, in front of his spine.

"My doctor said he has never seen a sarcoma that is this big, grows this fast and is well hidden," Doc Willie added.

In a more recent video, Doc Willie shared that the sarcoma was blocking his esophagus, making it hard for him to swallow his food.

Johns Hopkins Medicine describes sarcomas as "rare cancers that develop in the bones and soft tissues, including fat, muscles, blood vessels, nerves, deep skin tissues and fibrous tissues."

It added that bone sarcomas are more common among children, while soft tissue sarcomas are more common in adults.

The former are primary bone tumors, with the most common form of primary bone cancer being osteosarcoma, while the latter originate in the body's soft tissues and are most commonly found in the arms, legs, chest, or abdomen.

Related:  Health advocate Willie Ong diagnosed with cancer

While there is no known cause for most sarcomas, the most common risk factors are long-term swelling in the arms or legs (lymphedema) and taking radiation therapy for previous cancers.

Genetic disorders like Von Recklinghausen's disease (neurofibromatosis), Gardner syndrome, Werner syndrome, tuberous sclerosis, nevoid basal cell carcinoma syndrome, and Li-Fraumeni syndrome or retinoblastoma also increase the risk of sarcoma.

Most are not associated with specific environmental hazards, though Johns Hopkins Medicine still noted that there are still risks when exposed to dioxin, arsenic, or vinyl chloride monomer (used to make some types of plastics).

Early symptoms of soft tissue sarcoma include a painless lump or swelling, some of which do not even show symptoms until they grow and press on neighboring nerves, organs, or muscles, which causes pain like difficulty breathing or feeling full.

Early signs of bone sarcomas include limited range of motion in a joint, unknown fever,