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One subtype of epithelial, or epithelioid, mesothelioma is known as adenomatoid mesothelioma. Also called glandular mesothelioma, this type of mesothelioma involves cells of the epithelial type. These are also classified as adenomatoid, which means these cells arise from the mesothelium of the body’s glands. Glands are small organs that produce and release hormones, including the testis, pancreas, and pituitary gland.
Adenomatoid tumors are often benign and commonly originate in the genital glands of male or female patients. However, these tumors can become malignant, metastasizing to the pleura. Some cases of malignant pleural mesothelioma have growth patterns characteristic of adenomatoid tumors. Because this type of cell growth can be either malignant or benign, diagnosing malignant forms is problematic but necessary for proper treatment.
An adenoma, or adenomatoid tumor, is a benign tumor that arises in the epithelial cells of a gland. These tumors may also develop in non-glandular tissues. However, when this occurs, they will show signs of gland-like cell patterns and growth. Some common body areas adenomas originate include the genital tracts of both men and women. Many of these tumors seem to include tissue from the mesothelium, although others do not. Adenomas, therefore, may or may not be classified as mesothelioma.
When an adenomatoid tumor transitions from benign to malignant, it is called an adenocarcinoma. This type of tumor can spread or metastasize to other organs, including the pleura. Mesothelioma in the pleura that has adenomatoid cells may be the result of metastasized adenocarcinoma. In other words, the cancer originated elsewhere, eventually spreading to the pleura.
Pleural Adenomatoid Mesothelioma
If the adenocarcinoma found in the pleura did not originate and metastasize elsewhere, it is considered an adenomatoid mesothelioma. This is true mesothelioma originating in the pleura with characteristics of adenomatoid, or glandular, cancer cells. The growth pattern of this type of mesothelioma is of tubular spaces that are lined with epithelial cells. This looks similar to the pattern seen in benign adenomas and malignant adenocarcinomas.
Because adenomatoid cells in mesothelioma can have a variety of origins, diagnosis can be problematic. The malignant cells mimic benign cells, making it difficult to tell if the cells originated as an adenocarcinoma and spread to the mesothelium, or if they originated in the pleura or other part of the mesothelium.
Diagnosis begins with a physical exam, description of the typical symptoms, imaging scans, and biopsies. These procedures help doctors make a diagnosis of mesothelioma. However, histological study, or examination of the tumor and fluid cells under the microscope, is crucial to diagnosing the specific type of mesothelioma.
Since cell structure and growth patterns of adenomatoid mesothelioma mimics other types of tumors, basic histological study of biopsied samples may not be sufficient. Research has shown immunohistochemical staining and examination can distinguish between cells originating in the mesothelium and those that metastasized from elsewhere, as well as those that are benign. Immunohistochemical staining uses specific antibodies to target cellular components characteristic of a cell type. This diagnostic tool helps doctors identify cell type more accurately.
If adenomatoid cells found in the tumors of the pleura or other part of the mesothelium are determined to be benign, treatment is clear. Surgery is generally used for tumor removal and to prevent further growth of the abnormal cells. If it is a true malignant mesothelioma, the treatment is similar to treatments for other types of this cancer, including surgery, chemotherapy, and radiation.
Unfortunately, the prognosis is not usually good for most cases of adenomatoid mesothelioma. Most are found to be malignant. In one study, participants being studied for adenomatoid mesothelioma tumors received treatment but lived an average of ten months after the initial diagnosis.
Page Medically Reviewed and Edited by Pinar Kanlikilicer, PhD
Dr. Pinar Kanlikilicer has a PhD in Biomedical Engineering. She completed her 5-years of postdoctoral training in the Department of Experimental Therapeutics at MD Anderson Cancer Center. She is currently working in the field of cancer as a research scientist.