Clinicopathological analysis and literature review of a case of left atrial myxoma exhibiting chondroid metaplasia (low malignant potential)

Abstract: Left atrial myxoma with chondroid metaplasia (low malignant potential) is an extremely rare variant. This study aimed to investigate its clinicopathological features, diagnostic criteria, and differential diagnosis for accurate clinical diagnosis, treatment optimization, and prognostic evaluation. Clinical data, imaging findings, and pathological specimens of a 39-year-old male patient with left atrial tumor were retrospectively analyzed. H and E staining and EnVision-based immunohistochemical staining were performed for S100, CD34, SOX10, Mucin-4, SMA, and Ki67. Relevant literatures were systematically reviewed. The patient presented with chest tightness and dyspnea. Preoperative imaging revealed a left atrial mass with calcification, and intraoperative findings confirmed tumor invasion of the anterior mitral leaflet and annulus. Grossly, the tumor had a complete capsule, grayish-white cut surface with focal myxoid areas. Microscopically, the tumor was composed of mature cartilaginous tissue (about 40%), spindle cell stroma, and myxoma-like matrix in a transitional growth pattern. Immunohistochemically, the Ki67 proliferation index in hotspots was 40%. The final diagnosis was left atrial myxoma with chondroid metaplasia (low malignant potential). This rare subtype requires comprehensive clinical, imaging, and pathological evaluation. High Ki67 proliferation activity and local invasiveness indicate low malignant potential. Long-term follow-up and supplementary molecular testing are essential for prognostic assessment.