Calcified amorphous tumor in a patient receiving peritoneal dialysis with severe, treatment-refractory...

Calcified amorphous tumors (CATs) are rare, non-neoplastic intracardiac masses first described by Reynolds et al. in 1997. Although increasingly reported, their pathogenesis remains poorly understood, and they are frequently misdiagnosed as vegetations, cardiac myxomas, or malignant tumors. Proposed mechanisms include abnormalities in calcium-phosphate metabolism and hypercoagulable states. We report a case of CAT formation in a patient receiving peritoneal dialysis with severe, refractory hyperphosphatemia. A 47-year-old woman with type 2 diabetes mellitus, hypertension, heart failure with reduced ejection fraction, and end-stage renal disease on peritoneal dialysis had unremitting hyperphosphatemia (>10 mg/dL). Phosphate control was limited despite having trialed sevelamer and calcium acetate and intolerance to tenapanor due to gastrointestinal adverse effects. She had mixed adherence to dietary recommendations. She presented with leg pain and imaging raised concern for a psoas abscess. As part of an infectious embolic evaluation, transthoracic echocardiography revealed mitral valve dysfunction caused by a mobile intracardiac mass. Surgical resection was performed, and histopathologic examination confirmed a CAT. CATs typically present with symptoms related to valvular obstruction or embolization. Imaging findings on echocardiography, computed tomography, or magnetic resonance imaging are nonspecific, making histopathology essential for definitive diagnosis. Surgical excision remains the treatment of choice, with recurrence reported rarely. Given the propensity for calcium-phosphate deposition in patients with chronic hyperphosphatemia, strict phosphate control may reduce the risk of CAT development in patients with end-stage renal disease, though further studies are needed to clarify preventive strategies.