Multilocular thymic cyst in a HIV positive adult man detected during COVID-19 treatment: A case report and literature review

Background: Multilocular thymic cysts (MTC) are rare mediastinal tumors with multiloculated cyst-like structures in the anterior mediastinum. It is associated with a good prognosis when accurately diagnosed using needle biopsy or surgical removal but must be carefully differentiated from other cyst-forming tumors such as thymoma, thymic carcinoma, Hodgkin lymphoma, and seminoma. MTC is associated with inflammatory diseases, such as Sjogren’s syndrome and human immunodeficiency virus (HIV) infection. To date, only 15 cases of HIV infection have been reported in adult patients, and most cases show HIV infection-related symptoms such as lymphoid interstitial pneumonia and parotid gland enlargement. We report a case of asymptomatic MTC in an HIV-positive adult patient treated for coronavirus disease 2019 (COVID-19). Case presentation: An anterior mediastinal tumor was incidentally detected on computed tomography of a 52-year-old man with a 20-year history of HIV infection during COVID-19 treatment. The patient was asymptomatic with no notable physical findings. Magnetic resonance imaging revealed a 28 mm bilocular cyst. Robot-assisted thoracoscopic tumor resection was performed. Intraoperatively, the tumor was found to be a cystic lesion within the thymus, and the thymic tissue showed hyperplasia and diffuse smaller cystic changes. Pathological examination showed that the cysts were lined with squamous or cuboidal epithelium, and the cyst wall was mainly composed of thymic tissue with follicular hyperplasia. Hassall’s corpuscles and cholesterol granulomas are also observed. Signs of malignancy were not observed. Based on these findings, the patient was diagnosed with MTC. The patient is currently being followed up at an outpatient clinic without any signs of recurrence. Conclusion We report a case of MTC detected during COVID-19 treatment in an adult HIV-positive patient. Accumulation of cyst formation cases in COVID-19 patients is needed to elucidate the relationship between MTC and COVID-19.