Perisplenic mass as initial diagnosis of malignant peritoneal mesothelioma

Perisplenic masses or collections are rare findings on imaging examinations. The differential diagnostic spectrum is broad. We report the case of an 84-year-old man who presented to our emergency department with fatigue, unwanted weight loss, loss of appetite and abdominal pain. In B-mode ultrasound a very hypoechoic collection circularly located around the spleen was seen. A splenic hematoma or an abscess were primarily suspected. Performing contrast-enhanced ultrasound examination the perisplenic collection was surprisingly strongly contrasted in the arterial phase. An additional abdominal CT confirmed the mass in the left upper abdomen circularly around the spleen, compressing the left colic flexure and beginning to infiltrate the gastric fundus. An ultrasound-guided tissue biopsy was taken via a percutaneous intercostal approach, which resulted in the diagnosis of a low-grade epithelioid malignant peritoneal mesothelioma (MPM). MPM often presents with diffuse multifocal involvement of the peritoneal lining, however a unifocal manifestation of MPM is uncommon in general. A perisplenic mass manifestation of malignant peritoneal mesothelioma is an extremely rare occurrence. This case highlights the diagnostic challenges posed by the rare perisplenic manifestation of MPM.