Angiosarcoma: What we know about soft tissue cancer that claimed King Oyo

The death of King Oyo Nyimba Kabamba Iguru Rukidi IV has drawn attention to angiosarcoma, a rare and aggressive form of cancer that his family says claimed his life after months of treatment in Uganda, Germany and the United States.

Princess Ruth Komuntale, the late king’s sister, revealed during his burial ceremony in Fort Portal that Oyo was diagnosed with angiosarcoma in October 2025 after more than a year of seeking medical attention for different pains.

“Before his diagnosis he had spent more than a year seeking medical evaluations here in Uganda for the different pains he was experiencing,” she said.

“Sadly he was not getting the correct diagnosis, he was told that his pain was likely related to strenuous exercises or ulcers and was advised to undergo physiotherapy. By the time he got the correct diagnosis the cancer had already spread, and was affecting multiple organs.”

Angiosarcoma is a rare cancer that develops in the lining of blood vessels and lymph vessels. Because these vessels are found throughout the body, the disease can occur in different organs and tissues. It is classified as a type of soft tissue sarcoma. 

King Oyo died on August 27, 2026, aged 34, while receiving treatment in the United States. He had ruled Tooro since 1995 after becoming the world’s youngest reigning monarch at the age of three. 

Komuntale told mourners that after starting on specialised treatment, the king’s condition improved, giving the family hope.

“After he began getting the correct treatment the cancer cells started showering dramatically and he gained energy. Those improvements gave us hope that he was to get better,” she said.

However, she said his condition worsened in July 2026 as the cancer progressed.

“The cancer had been in his body too long and despite everything that was done his condition became increasingly difficult,” she said.

Angiosarcoma begins when cells that line blood vessels or lymph vessels undergo changes that cause uncontrolled growth. The cancer can invade surrounding tissues and spread to other parts of the body. 

Doctors say it is uncommon and often difficult to diagnose because symptoms vary depending on where the cancer develops. 

In some cases, it appears on the skin as a bruise-like mark, swelling or a growing lesion. When it develops deeper inside the body, symptoms may include pain or problems linked to the affected organ. 

Soft tissue sarcomas, including angiosarcoma, can be difficult to identify because they may resemble other conditions. A lump, persistent swelling, unexplained pain or unusual skin changes may require further medical investigation. 

In many cases, doctors do not know what causes angiosarcoma. However, researchers have identified some factors linked to higher risk, including previous radiation treatment, chronic swelling caused by lymph vessel damage and exposure to certain chemicals such as vinyl chloride and arsenic. 

Treatment depends on where the cancer develops, its size and whether it has spread. Options may include surgery, chemotherapy, radiation therapy and targeted treatments. However, treatment becomes more complicated when the disease has spread to several parts of the body. 

Komuntale said despite his illness, King Oyo remained strong in faith and continued praying and studying the Bible.

King Oyo’s death marked the end of a 30-year reign that began when he inherited the Tooro throne as a child. His burial was held on September 12, 2026, at the Karambi Royal Tombs in Fort Portal