Regressed anterior mediastinal nodule secondary to removal of dental crowns.

The causality of thymoma (TM) or thymic hyperplasia and various autoimmune diseases (AISs) remains poorly understood. To date, there have been no confirmed cases of pathologically complete regression of TM. We present a rare case of complete regression of an anterior mediastinal tumour secondary to the removal of metallic dental crowns as a treatment for metal allergy assessed to exacerbate pityriasis rubra pilaris, a rare cutaneous disease. After dental crown removal, the skin lesions improved, and the anterior mediastinal nodule (AMN) shrank rapidly through transient enlargement with a low density in the central area. Despite observation being an option, the patient preferred surgical resection and pathological examination, which revealed no remnant neoplasm. Treatment for skin conditions rarely induces complete regression of the AMN. This case highlights the potential novel link between anterior mediastinal tumours and AISs, including cutaneous disorders, and raises awareness amongst clinicians of this possible association.