Mesothelioma cells are the cells that cause mesothelioma, a rare and aggressive cancer. This malignancy originates from the mesothelium, a protective membrane lining various internal organs and body cavities. Understanding these cells is key to understanding this disease.
What Are Mesothelioma Cells?
Mesothelioma cells develop from normal mesothelial cells, which form protective linings around organs. These linings include the pleura surrounding the lungs, the peritoneum enclosing abdominal organs, the pericardium around the heart, and the tunica vaginalis covering the testicles.
The transformation of healthy mesothelial cells into malignant ones is primarily linked to asbestos exposure. Asbestos fibers, when inhaled, can reach the pleural space and cause tissue damage and inflammation, leading to mesothelioma after a long latency period. Unlike healthy cells, mesothelioma cells grow uncontrollably and have an abnormal structure, forming tumors.
Types and Characteristics of Mesothelioma Cells
Mesothelioma cells are categorized into three main types based on their appearance: epithelioid, sarcomatoid, and biphasic. Epithelioid cells are the most common, accounting for 50-70% of cases, and are cuboidal or oval-shaped, resembling epithelial cells. These cells grow in sheets, clusters, or gland-like structures. Their tendency to stick together can slow their spread, making them more responsive to treatment.
Sarcomatoid cells are less common, making up about 10-20% of cases, and are characterized by their elongated, spindle-shaped appearance, resembling connective tissue cells. These cells are more aggressive and challenging to treat, spreading rapidly and forming new tumors. Biphasic mesothelioma, comprising 20-30% of cases, contains a mixture of both epithelioid and sarcomatoid cells. The proportion of each cell type influences the disease’s behavior and response to therapy, with a higher percentage of epithelioid cells correlating with a better prognosis.
How Mesothelioma Cells are Identified
The identification of mesothelioma cells relies primarily on tissue or fluid samples obtained through a biopsy, followed by microscopic examination, known as histopathology. Pathologists analyze these samples to distinguish malignant mesothelioma cells from other types of cancer cells, such as adenocarcinoma, or from benign inflammatory changes in the mesothelium. Distinguishing them can be challenging due to overlapping features.
To enhance diagnostic precision, specialized staining techniques, particularly immunohistochemistry (IHC), are used. IHC uses antibodies that bind to specific proteins, or markers, present in the cells, making them visible under a microscope. Common markers that help confirm the presence of mesothelioma cells include calretinin, cytokeratin 5/6 (CK5/6), and WT-1 (Wilms’ tumor-1 antigen). While some markers, like mesothelin and podoplanin (D2-40), are also indicative, a panel of multiple markers is used to improve diagnostic accuracy and differentiate mesothelioma from other malignancies.
Behavior and Growth of Mesothelioma Cells
Once mesothelial cells undergo malignant transformation, they exhibit characteristic growth patterns and invasive behaviors. Instead of forming a localized mass, mesothelioma cells typically grow in sheets or nodules along serosal surfaces, such as the pleura or peritoneum. This diffuse growth allows them to spread locally within the affected body cavity, enveloping organs like the lungs or abdominal viscera.
The invasive nature of these cells contributes to the disease’s aggressiveness. They penetrate surrounding tissues and structures, contributing to treatment challenges. Mesothelioma cells also proliferate aggressively and resist conventional therapies, making the disease particularly difficult to manage. The tumor microenvironment, including the extracellular matrix and stromal cells, plays a role in promoting tumor growth, invasion, and protecting against immune responses, further contributing to this resistance.