Multilocular Thymic Cyst with High F¹⁸ Fluorodeoxyglucose Uptake and Rheumatoid Arthritis: A Case Report

Area of Science:

• Thoracic Surgery
• Rheumatology
• Pathology

Background:

• Multilocular thymic cysts are uncommon acquired cysts in the anterior mediastinum.
• These cysts result from incomplete thymic involution and can be associated with autoimmune diseases like rheumatoid arthritis and systemic sclerosis.

Observation:

• A 61-year-old male with an 8-year history of rheumatoid arthritis presented with an anterior mediastinal mass.
• The mass showed high F18-fluorodeoxyglucose uptake on PET-CT, indicating potential malignancy or significant inflammation.
• Histological examination revealed a multilocular thymic cyst with prominent lymphoid tissue.

Findings:

• Surgical excision of the multilocular thymic cyst was performed.
• The patient experienced a progressive disappearance of rheumatoid arthritis-related symptoms post-surgery.

Implications:

• This case suggests a potential link between multilocular thymic cysts and rheumatoid arthritis activity.
• Surgical removal of these cysts may lead to clinical improvement in associated autoimmune conditions.
• This is the first reported instance of rheumatoid arthritis symptom improvement following multilocular thymic cyst excision.