In a recent study titled “Positive TTF-1 Expression in Malignant Mesothelioma: A Case Report” and published in the American Journal of Case Reports, the study’s authors report the first case of a patient with malignant mesothelioma whose tumor cells express the transcription factor TTF-1.
Malignant mesothelioma is a rare cancer caused by frequent exposure to asbestos — a natural yet toxic mineral that was frequently used in many industries, especially construction. When inhaled, these fibers cannot be broken down in the body or expelled and, as a result, lead to harmful inflammation and scarring of the mesothelium, ultimately progressing to malignant mesothelioma or other other respiratory conditions, such as asbestosis.
Although rare, its incidence is increasing worldwide. It is widely accepted that the lung’s parietal pleura (the outer membrane which is attached to the inner surface of the thoracic cavity) is the tissue altered in malignant mesothelioma. But there are also cases of peritoneal mesothelioma, which forms in the protective membrane that surrounds the abdomen. This is usually caused when people cough up and swallow inhaled asbestos fibers
For correct diagnosis and treatment, it is important to distinguish malignant mesothelioma from other types of cancer, and this is achieved through established markers. With malignant mesothelioma, these markers include pancytokeratin, cytokeratin 5/6, calretinin, WT-1, D2-40, BG8, MOC-31, EpCAM (BerEP4), Claudin, and TTF-1. In fact, TTF-1 (short for thyroid transcription factor-1) is present in roughly 85 percent of lung adenocarcinoma and in thyroid carcinoma cases, but is generally absent in other forms of cancer.
In this study, authors describe a case report of a 70-year-old white female with a right paravertebral rapidly growing tumor and severe pain, later diagnosed as malignant mesothelioma. Following immunohistochemical analysis, they found that this patient’s malignant mesothelioma was positive for TTF-1 expression. This is the first case of malignant mesothelioma expressing TTF-1 (TTF-1 is a transcription factor essential for the morphogenesis and differentiation of several organs, including the lungs, ventral forebrain, and thyroid).
This is the first case of a malignant mesothelioma with immunohistochemical positive expression of TTF-1. These results suggest that, contrary to what has happened before, a positive reaction for TTF-1 in tumor cells may not exclude a malignant mesothelioma.