Lymphoid follicular hyperplasia arising from the chest wall presenting as a substantial mass

Lymphoid follicular hyperplasia (LFH) is a benign lymphoproliferative disease. Although it can occur within the thoracic cavity, LFH originating from the chest wall has not been reported. A 79-year-old woman was incidentally found to have a well-defined mass on the left posterior chest wall during a preoperative examination for aortic valve replacement. The mass had slowly grown over 6 years. Thoracoscopic surgical resection was performed without complications. Pathological examination ruled out lymphoproliferative diseases, such as Castleman disease or malignant lymphoma, and a diagnosis of LFH was made. Although LFH generally has a good prognosis, surgical resection is recommended for diagnostic and therapeutic purposes owing to the possibility of malignancy masquerading as a reactive lesion. This is the first report of an LFH arising from the chest wall with imaging findings similar to other benign tumours. Its potential as a differential diagnosis for tumours with similar imaging findings is highlighted.