Giant cervicomediastinal thymic cyst in an elderly: diagnosis by multimodality imaging and fine-needle aspiration cytology with immunocytochemistry

A 65-year-old woman, a non-smoker, presented to the pulmonary medicine outpatient department with chest pain, mild dyspnoea, right side neck swelling and mild facial puffiness. The cervical swelling was soft, non-tender and fluctuant on palpation. Multimodality imaging revealed a large, thin-walled cervicomediastinal cystic lesion with septations, haemorrhage, septal calcification and without any solid component. Image-guided fine-needle aspiration cytology from the septa with immunocytochemistry helped to establish the thymic origin and benign nature of the cyst preoperatively and differentiate it from cystic thymoma, lymphangioma, thymic carcinoma or lymphoma with confidence. As the haemorrhage resolved, the size of the swelling was significantly reduced, and the patient became asymptomatic due to which she deferred surgery but remained on close follow-up and was doing well. Thymic cysts can occur in a cervicomediastinal location, rare in elderly age, usually asymptomatic and clinically apparent when intracystic haemorrhage leads to an increase in size and chest pain.