Adenomatoid mesothelioma arising from the diaphragm: a case report and review of the literature

Abstract

Background: Adenomatoid mesothelioma is a rare subtype of malignant mesothelioma that can be confused with adenomatoid tumors, which are classified as benign. The clinical features and optimal management of adenomatoid mesothelioma have not been elucidated in the literature. In this report, we present an extremely rare case of adenomatoid mesothelioma that developed on the peritoneal surface of the diaphragm as well as a literature review of adenomatoid mesothelioma in the abdominal cavity.

Case presentation: The patient was a 61-year-old Japanese woman who had undergone resection of a malignant peripheral nerve sheath tumor of the hand 18 years prior. She was diagnosed with clinical stage I lung adenocarcinoma on follow-up chest radiography. Simultaneously, a 20-mm enhancing nodule with slow growth on the right diaphragm was detected on contrast-enhanced computed tomography. She presented no specific clinical symptoms. At this point, the lesion was suspected to be a hypervascular tumor of borderline malignancy, such as a solitary fibrous tumor. After a left upper lobectomy for lung adenocarcinoma, she was referred to our department, and laparoscopic tumor resection was performed. Adenomatoid tumors were also considered based on the histopathological and immunohistochemical analyses, but we made the final diagnosis of adenomatoid mesothelioma using the results of the genetic profile. The patient remains alive, with no recurrence noted 6 months after surgery.

Conclusion: We encountered a valuable case of adenomatoid mesothelioma of peritoneal origin. There are some previously reported cases of adenomatoid mesothelioma and adenomatoid tumors that may need to be recategorized according to the current classification. It is important to accumulate and share new findings to clarify the clinicopathological characteristics and genetic status of adenomatoid mesothelioma.

Keywords: Adenomatoid mesothelioma; Adenomatoid tumor; Diaphragm; Mesothelial tumor; Peritoneal.

Fig. 1

Preoperative examination. a Contrast-enhanced computed tomography revealed a tumor (arrow) with marked enhancement in the arterial phase of the right diaphragm. b 18-Fluoro-2-deoxyglucose positron emission tomography image revealed that the maximal standard uptake value of nodule (arrow) was 3.5. c Ultrasonography showed a low-echoic lesion. d Early enhancement was observed in Sonazoid-enhanced ultrasonography

Fig. 2

Intraoperative findings. a A pedunculated tumor with a thin pedicle originating from the peritoneal surface of the right diaphragm. b The pedicle of the tumor was clipped, and the tumor was excised

Fig. 3

Macroscopic and microscopic findings of the resected tumor. a Macroscopic findings revealed a 28 × 20 × 11 mm³ brown–red tumor with a smooth cut surface. b Microscopic findings revealed papillary architecture with focal small aggregates of mesothelial cells. c Tumor cells were positive for cytokeratin 5/6. d Tumor cells were partially positive for calretinin. e Tumor cells were negative for carcinoembryonic antigen. f Tumor cells were negative for thyroid transcription factor-1. g Tumor cells were negative for cluster of differentiation 34. h Tumor cells were negative for signal transducer and activator of transcription 6