Micronodular thymoma is a rare subtype of thymoma with less than 20 cases published in the English literature. These tumours have been reported with thymoma or thymic cyst. The authors describe a new case of micronodular thymoma in a 68-year-old-patient which is well documented and particular by its cystic degeneration which hasn’t been described yet. Micronodular thymoma is a rare variant of thymoma with a challenging diagnosis. Clinicians must be aware of this entity in order not to confuse it with a thymic cyst.