Invasive thymoma with multiple ring calcifications and osseous metaplasia: A case report

An 8.0 × 7.0 × 3.0 cm calcified anterior mediastinal mass was found in a 57‐year‐old man during a regular health checkup. The tumor had invaded the pericardium and phrenic nerve. The Masaoka–Koga classification was stage III. Multiple ring calcifications were present in the gross feature, and osseous metaplasia was observed in the histologic examination. World Health Organization histologic classification of the tumor was type B2. The patient is currently undergoing chemotherapy and radiation therapy to prevent tumor recurrence. To our knowledge, this is the first case of multiple ring calcifications and osseous metaplasia in invasive thymoma.