Arising Mediastinal Adenocarcinoma in A Patient With A 14 Years History of Mature Teratoma.

Mature teratomas are typically benign germ cell tumours (GCT), but in rare cases, they can undergo malignant transformation. Malignant transformation of a mediastinal teratoma into adenocarcinoma is extremely rare and often poses diagnostic and therapeutic challenges. A 38-year-old male with a 14-year history of a mature mediastinal teratoma, developed a mediastinal adenocarcinoma. The patient initially underwent surgical resection of the teratoma, with no evidence of malignancy at that time. Over the years, the patient remained asymptomatic until the recent onset of cough, prompting further investigation. Imaging studies revealed a recurrent mediastinal mass, and subsequent biopsy confirmed adenocarcinoma arising from the previously diagnosed teratoma. The patient underwent debulking thoracotomy and chemotherapy. This case highlights the importance of long-term follow-up in patients with mediastinal teratomas, given the rare but significant risk of malignant transformation. Awareness of this possibility can facilitate early diagnosis and timely intervention, ultimately improving patient outcomes.