The patient was a 78-year-old male.
Chief complaint Asymptomatic.
History of present illness The patient was diagnosed with rectal GIST 20 years ago and received an endoscopic resection. Five years ago, he underwent total anorectal partial mesolectal resection (TAMIS), open pancreaticoduodenectomy and splenectomy. Two years ago, he underwent transanal resection of recurrent rectal GIST. Three months ago, left ventricular myocardial metastasis was suspected by thoracoabdominal contrast-enhanced CT. Adjuvant imatinib was withdrawn due to the appearance of skin symptoms along with tearing and itching of the eyes. The patient was referred to our department for resection.
Medical history Rectal GIST, COVID-19, Klebsiella pneumoniae, transit ischemic attack.
Allergy Imatinib (skin symptoms, eye symptoms).
Transthoracic echocardiogram There was a 12-mm limbic, clear, low-echoic area on the lateral wall of the left ventricle (Fig. 1). The left ventricular end-diastolic diameter was 42 mm. The left ventricular end-systolic diameter was 29 mm. The left ventricular ejection fraction (modified Simpson) was 60%. The IVC was 15 mm. E/A was 0.90. E/E' was 10.3. The heart valves worked correctly. The left ventricular wall motion was normal.
CT Left ventricular mass (11 × 11 mm) (Fig. 2).
PET image High degree of FDG accumulation in the left ventricular myocardium (Fig. 3).
Operative findings The patient was approached through a midline sternal incision, and extracorporeal circulation was established. The ascending aorta was clamped, and myocardial protection fluid was infused in both the antegrade and retrograde directions to arrest the heart. When the heart was arrested, a circular mass was observed at the end of the diagonal branch (Fig. 4A). It felt like hard rubber to the touch. The mass was trimmed in the shape of a tear drop and resected from the left ventricular wall with a sharp-edged knife (Fig. 4B). A part of the mass had extended into the left ventricular cavity. A 10-mm felt was placed around the resected hole, and the felt was threaded and closed with a 4–0 polypropylene horizontal mattress suture and continuous suture (Fig. 4C). The operation time was 2 h and 39 min, the total extracorporeal circulation time was 60 min, and the aortic clamp time was 32 min.
Postoperative course The pathological findings were negative for tissue fragments. The patient was discharged home on the 12th postoperative day without any complications. Postoperative transthoracic echocardiography showed that the left ventricular end-diastolic diameter (41 mm), left ventricular end-systolic diameter (29 mm) and left ventricular ejection fraction (60%) were not changed. The heart valves worked correctly. The wall motion of the left ventricle at the myectomy site was significantly (mildly to moderately) reduced, but the patient had no symptoms.
Excised specimen The tumor was well defined, with some necrosis. The tumor diameter was 12 × 24 × 13 mm (Fig. 5).
Histopathological examination revealed nodular tumor growth consisting of bundles of spindle-shaped cells in the myocardium (Fig. 6). Hyaline degeneration and focal hemorrhage were scattered in the tumor. The tumor showed an increased chromatin volume, but there was no significant cellular atypia or increased mitotic figures that would indicate sarcoma. On the specimen, the margins were negative. Immunostaining was positive for c-KIT (CD117) (Fig. 7) and CD34 (Fig. 8).