Cardiac Magnetic Resonance Characterization of Rare Myocardial Tumoral Infiltration of The Right-Sided Chamber Free Wall in a Patient With Buccal Mucosa Squamous Cell Carcinoma

Description of Clinical Presentation: A 66-year-old female patient with buccal mucosa squamous cell carcinoma, staged as pT3N0M0 (tumor >=4 cm [T3], without lymph node [N0] or distant organ [M0] involvement), underwent surgical treatment in February 2024. After five months, vertebral metastases were diagnosed. In October 2024, she was hospitalized with progressive asthenia, dyspnea, and clinical signs of cardiac tamponade. Transthoracic echocardiography revealed a large pericardial effusion associated with a solid right ventricular mass measuring up to 22 mm in thickness. She underwent a pericardial window procedure with drainage, yealding sero-hemorrhagic pericardial fluid negative for malignant cells. Endomyocardial biopsy was contraindicated due to the high risk of bleeding and systemic embolization. Than a cardiac magnetic resonance (CMR) was performed for further characterization of the mass in November 2024 with a 3 Tesla equipment. The findings, in the clinical context were most consistent with metastatic myocardial infiltration, although infectious etiologies such as fungal myocarditis remained a differential consideration. Given the CMR result, chemotherapy with carboplatin, 5-fluorouracil, and pembrolizumab was continued. Follow-up CMR in February 2025 showed significant tumor reduction (≈42×22×17mm) although new moderate left ventricular systolic dysfunction with ejection fraction (EF) of 44%, with diffuse hypokinesia.

Diagnostic Techniques and Their Most Important Findings: A dedicated tumor characterization protocol was applied, including localizers, cine sequences, double and triple inversion recovery (IR), T2 mapping, tumor perfusion, and late gadolinium enhancement (LGE). Cine sequences demonstrated a solid infiltrative mass isointense to the myocardium, localized in the right-sided free wall (≈55×27.5×26.5mm) with pericardial adhesion and mid-right coronary artery involvement, associated with a pedunculated mobile component. Right ventricular function was preserved (EF 55%), with impaired relaxation determined by mass. Left ventricle showed preserved size and systolic function (EF 55%). On double IR, the lesion appeared isointense to the myocardium, while triple IR showed hyperintensity. The T2 mapping had increased values, within the tumor (77ms) compared to myocardium (45ms). Perfusion demonstrated low vascularization of the mass. LGE revealed areas of necrosis, cystic and liquefactive componentes within the tumor, justifying the elevated T2 mapping values.

Learning Points from this Case: This case illustrates the pivotal role CMR in the noninvasive characterization of cardiac masses in oncologic patients, particularly when endomyocardial biopsy is contraindicated. It gives detailed information on tumor morphology, local extension, and coronary artery involvement. The serial follow-up demonstrated its utility in monitoring therapeutic response and complications. Cardiac metastases from buccal squamous cell carcinoma are exceedingly rare, and few reports in literature details CMR findings at diagnosis and follow-up exam.

Panels A–D: Cine CMR showing a right ventricular two-chamber long-axis view (A), a short-axis view (B), and a four-chamber view (C), depicting the tumor and a pedunculated lesion; and Triple IR sequence in a right ventricular two-chamber view (D), demonstrating high signal within the tumor.
Panels E–H: Triple IR (E) and Double IR (F) sequences showing high signal in Triple IR; perfusion imaging (G) demonstrating poor tumor vascularization; and T2 mapping (H) with ROIs placed in the interventricular septum and in the tumor mass, showing increased T2 values within the tumor region.
Panels I–L: Late gadolinium enhancement (LGE) sequences in four-chamber (I, J) and right ventricular two-chamber long-axis (K) views, demonstrating areas of necrosis and liquefaction; follow-up imaging (L) shows reduction of the tumor mass.