GCT of the bone is a type of rare, locally aggressive, intermediate tumor of the bone that generally impacts the rounded ends of long bones (also called the epiphyseal location). 12% of patients present with a pathological fracture, while other common symptoms include bone pain, swelling, tenderness, limited range of motion, and inability to weight-bear (1). In ~5% of patients, tumors can spread (metastasize) to the lungs (2,3). GCT of the bone are graded based on aggressiveness of the tumor behavior, this grading impacts prognosis and lung metastasis risk. To learn more about grading at Grade of GCT.
GCT of the bone varies in clinical presentation and can occur at any age. The median reported age at diagnosis is 35 years old with a range between 9-77 years old (4). However, most patients are diagnosed between their 2nd and 5th decade of life (5).
GCTs are rare and researchers don’t know exactly how many people are diagnosed with GCT of the bone each year. However, a study done in the Netherlands was used to help calculate incidence. It is estimated that 1.4-2.1 people out of every million are diagnosed with GCT per year (4). Additionally, there is a higher predominance in females, with a ratio of 1.4:1 males.
Surgery may be curative for many people with GCT of the bone, but for others, tumors may recur after surgery. Recurrence rates vary based on tumor location and type of treatment. Recurrence has been noted somewhere between 6-45% depending on the literature (5,6,7). Different types of doctors are likely to be involved in the care of people with GCT of the bone. For hard-to-treat cases, care teams may include sarcoma specialists. These doctors have experience treating tumors similar to GCTs.
The World Health Organization classifies GCT of the bone as an intermediate tumor. This means that these tumors rarely spread and are locally invasive (7). These tumors are benign but may share similar features to cancer, also referred to as sarcoma. However, it is important to note that these tumors are not cancerous. For example, GCTs can invade healthy tissue leading to bone decay and destruction. However, GCTs typically does not pose a threat to your life like cancer can. Left untreated, GCTs can lead to loss of limb, loss of function, and can drastically influence quality of life.
GCT of the bone is treated with surgery as the standard of care, however, there are medications for recurrent and/or inoperable GCT of the bone. The best treatment modality is currently highly debated as scientific literature remains in poor quality and scarce. To learn more, go to Treatment.
What makes up gct of the bone?
There are hundreds of different types of cells in the body. All of these different cells serve a specific and diverse function. The cells within a GCT are just as diverse. Tumors can begin in almost any type of cells in the body.
The type of cell defines the biology of the tumor and the location can influences the treatment plan. There are 3 types of cells in these tumors that resemble fibroblasts and stromal cells (Type I), monocytes and macrophages (Type II), and osteoclasts (Type III).
Type I (Fibroblasts & Stromal cells): Fibroblasts are a type of connective tissue cell that produces collagen. Stromal cells are a type of connective tissue that supports bones and organs (8). These cells have the ability to grow and make up part of the bulk tumor. The stromal cells often (>90%) contain a mutation in how tightly the DNA is held, known as H3F3A mutation. This is a signature of GCT of the bone and often used for diagnosis (9). Go to Causes of GCT to learn more.
Type II (Monocytes and Macrophages): A monocyte is a type of white blood cell that can function as a macrophage. A macrophage is a specialized white blood cell involved in the inflammatory response. A small portion of the GCT of the bone is made up of monocytes and macrophages that are recruited to the tumor from the blood stream (10). These cells are also thought to be precursors to fully developed giant cells with multiple rounded centers.
Osteoclasts:An osteoclast is a type of cell with multiple rounded centers that dissolves and absorbs bone. GCT of the bone are osteoclast-like, meaning they have the ability to dissolve and absorb bone causing damage (11). GCT use this osteoclast-like feature to decay bone leading to breaks. To learn more, go to Causes of GCT.