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Vol.61 No.2 contents | Japanese/English |
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- Case Report -
Spontaneous Regression of Malignant Pleural Mesothelioma, Possibly Caused by CD8+ Tumor-infiltrating Lymphocytes
Yosuke Kakiuchi1, Hideshi Uramoto1, Takaaki Ito2, Sayuri Hirooka1, Kazuyoshi Nakamura1, Takako Matsuoka1, Osamu Sakamoto11Respiratory Medicine, National Hospital Organization Kumamoto Saishun Medical Center, Japan, 2Department of Pathology and Experimental Medicine, Kumamoto University Graduate School of Medical Sciences, Japan
Background. Malignant pleural mesothelioma is a disease with a poor prognosis and limited therapeutic options. With only a few reports available, spontaneous regression of malignancy is very rare, and the mechanism underlying spontaneous regression of malignancy is unknown. Case. A 68-year-old man was referred to our hospital because of dyspnea on exertion, anorexia, and weight loss. Chest computed tomography (CT) revealed multiple tumors in the pleura and interlobar pleura at the right side along with right pleural effusion. We performed a percutaneous needle biopsy of a pleural mass and thoracentesis. We finally diagnosed the patient with epithelioid malignant pleural mesothelioma, pathological T3N0M0 stage III. However, the patient's performance status was 3, so we concluded that chemotherapy would be difficult and suggested best supportive care instead. One year later, he was referred to our hospital again. Chest CT indicated that multiple tumor shadows on the pleura and interlobar pleura had been reduced and decreased despite no medical treatment, such as radiotherapy, chemotherapy, or immunotherapy. Thus, spontaneous regression of malignant pleural mesothelioma was considered to have occurred. Conclusion. Spontaneous regression of malignant pleural mesothelioma is very rare. CD8+ T cells are known to play a critical role in antitumor immunity. In our case, we performed immunohistochemical anti-CD8 antibody staining, and many tumor-infiltrating lymphocytes were stained. There was a significantly greater increase of CD8+ than CD4+ tumor-infiltrating lymphocytes. This significant increase in CD8+ tumor-infiltrating lymphocytes further supported the possibility that the spontaneous regression of the malignant pleural mesothelioma had been caused by the antitumor effect of CD8+ tumor-infiltrating lymphocytes. These findings suggest that the spontaneous regression of malignant pleural mesothelioma may have been caused by CD8+ tumor-infiltrating lymphocytes. The presence of CD8+ tumor-infiltrating lymphocytes may correlate with spontaneous regression and an improved clinical outcome.
key words: Malignant pleural mesothelioma, Tumor-infiltrating lymphocytes, Spontaneous regression
Received: September 6, 2020
Accepted: January 8, 2021
JJLC 61 (2): 130-137, 2021