Uterine cancer, also known as womb cancer, is a disease where abnormal cells grow in the uterus, the pear-shaped organ in a woman’s pelvis. Endometrial cancer, which originates in the lining of the uterus called the endometrium, accounts for approximately 90% to 95% of all uterine cancer cases. Understanding its spread is crucial for diagnosis and treatment planning. This article explores common patterns of spread, influencing factors, and detection methods.
Primary Pathways of Spread
Uterine cancer commonly spreads through several primary pathways. The cancer can extend directly from the uterine lining into the muscular wall of the uterus, known as the myometrium. From there, it may continue to grow into adjacent organs like the cervix, vagina, fallopian tubes, or ovaries.
Another common pathway for initial spread is through the lymphatic system. Cancer cells can detach from the primary tumor and enter lymphatic vessels. These cells then travel to regional lymph nodes. The pelvic lymph nodes, including those around the blood vessels within the pelvis (such as obturator, external iliac, and internal iliac nodes), are often the first sites where cancer cells are detected outside the uterus. Subsequently, cancer can spread to the para-aortic lymph nodes, which are located near the major blood vessels in the abdomen.
In some instances, cancer cells can shed directly into the abdominal cavity, leading to intraperitoneal spread. This occurs when cells break away from the uterus or ovaries and spread to the peritoneum, the membrane lining the abdominal cavity, or to other abdominal organs. This pathway is relevant for more aggressive types of uterine cancer.
Distant Metastasis
After initial local and regional spread, uterine cancer can advance to distant parts of the body through a process called hematogenous spread. This occurs when cancer cells enter the bloodstream and travel to organs far from the uterus.
The lungs are the most common site for distant metastasis of uterine cancer, occurring in approximately 29% of cases. Symptoms of lung involvement can include chest pain, coughing, or shortness of breath.
The liver is another frequent site for distant spread, observed in about 15% of metastatic cases. Beyond the lungs and liver, uterine cancer can also spread to the bones, accounting for about 10% of distant metastatic cases. Bone metastases can cause pain and may weaken the affected bones. The brain is a less common but possible site for distant spread, occurring in about 3% of metastatic cases, often in individuals with advanced, high-grade tumors.
Factors Influencing Spread
Several characteristics of uterine cancer can influence its likelihood and pattern of spread. The tumor grade describes how abnormal the cancer cells look and how quickly they are likely to grow and spread. Higher-grade tumors (grade 3) are more prone to spreading, particularly to lymph nodes, compared to lower-grade tumors.
The specific histology, or type, of uterine cancer also plays a role. While endometrioid adenocarcinoma is the most common type and generally less aggressive, certain subtypes like serous carcinoma and clear cell carcinoma are more aggressive and have a higher propensity for early spread, often presenting at an advanced stage.
The depth of myometrial invasion, or how deeply the tumor has grown into the muscular wall, is a significant factor. Deeper invasion increases the risk of cancer cells entering blood vessels or lymphatic channels, raising the risk of lymphatic or distant spread. Additionally, the presence of lymphovascular space invasion (LVSI), which means cancer cells are found within small blood vessels or lymphatic channels inside the tumor, indicates a higher risk of spread. Larger tumors or those diagnosed at a more advanced stage have a greater likelihood of having already spread beyond the uterus.
Detecting Spread
Detecting uterine cancer spread involves a combination of diagnostic methods. Imaging tests are frequently used to visualize the extent of the disease and identify any areas of spread.
Magnetic Resonance Imaging (MRI) of the pelvis is effective for detailed imaging of the uterus, nearby tissues, and pelvic lymph nodes. Computed Tomography (CT) scans of the chest, abdomen, and pelvis are utilized to check for cancer spread to other organs and lymph nodes throughout the body. Positron Emission Tomography (PET) scans, often combined with CT (PET-CT), can help identify small collections of cancer cells and are particularly useful for detecting metastatic lesions and lymph node involvement, although they are not typically used for initial screening.
When suspicious areas are identified through imaging, a biopsy is often necessary to confirm the presence of metastatic cancer. This involves taking a tissue sample from the suspicious area, such as a lymph node or a distant lesion, for microscopic examination. A physical examination, including a pelvic exam, also plays a role in identifying palpable lymph nodes or other signs that might suggest advanced disease.