Written By: Karen Selby, RN,
Last modified: September 21, 2021

Any type of mesothelioma can have an adenomatoid growth pattern. Pleural, peritoneal or pericardial mesotheliomas may all feature an adenomatoid differentiation.

This type of mesothelioma can mimic several other types of tumors, including benign adenomatoid tumors and pleural metastases of adenocarcinoma. To correctly diagnose a patient, doctors evaluate the patient’s clinical presentation as well as unique histological features of the tumor.

Growth Patterns

These cells can be either flat or cube-shaped. In adenomatoid mesothelioma, the cells line small, gland-like structures.

As with other types of epithelioid mesothelioma, adenomatoid cells grow in a uniform pattern. Some tumors grow into microcystic structures. These patterns can have a lace-like appearance.

Adenomatoid growth patterns may coexist with other growth patterns in epithelial tumors but are often the predominant pattern.

Benign Lesions vs. Malignant Tumors

Adenomatoid cells can occur in benign and malignant tissue. When these cells are found in the peritoneum they behave as benign lesions and respond well to treatment. However, adenomatoid cells found in the pleura could be benign or malignant.

Adenomatoid malignant mesothelioma is not the same thing as a benign adenomatoid mesothelial lesion. These lesions grow in mesothelial cells, but they have different cellular makeup than malignant tumors and behave as benign lesions.

Lesions typically develop in pelvic organs, but they can also arise in the pleura, mesentery or omentum. Similar to a benign tumor, these lesions are very small and lack significant cellular abnormalities.

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    Diagnosis and Treatment

    Malignant mesotheliomas are often diagnosed differently than benign lesions. The benign growths often develop in the genital tract (in both males and females), and they are often diagnosed incidentally during pelvic surgery. A handful of these benign lesions have also been detected in the pleura during a debulking surgery for other lung masses.

    Benign adenomatoid lesions have also appeared in the following locations:

    • Omentum
    • Mesentery
    • Pancreas
    • Liver
    • Bladder
    • Mediastinal Lymph Nodes
    • Adrenal glands

    However, when doctors diagnose a patient with malignant mesothelioma of the adenomatoid variety, the mesothelioma testing process is the same as it is for all of this disease’s types. Patients typically present with chest pain, shortness of breath and coughing. The oncologist then runs several imaging scans and biopsies that lead to diagnosis.

    Because adenomatoid mesotheliomas look very similar to benign lesions, doctors need to look for specific markers to differentiate between the two conditions. Doctors primarily look for pleural thickening and pleural nodules. These two characteristics are typically absent in cases of benign lesions. To diagnose lesions, doctors look for fibrous stroma (soft tissues) and bland, well-defined cell borders.

    However, a 2014 case report discusses a case of adenomatoid malignant mesothelioma that was identified with cytology tests of pleural effusion. The pleural fluid contained unusual features called intranuclear inclusion bodies among predominately adenomatoid cells. The case report authors recommended adding adenomatoid malignant mesothelioma to the list of differential diagnoses when pleural cytology tests reveal intranuclear inclusion bodies.

    While benign lesions are typically easy to remove through surgery, malignant tumors are more difficult to treat. Therapeutic options include surgery, chemotherapy and radiation therapy. However, one study showed that the mean survival of seven patients who received treatment for adenomatoid mesothelioma was 10 months from the time of diagnosis.

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