An Occult Primary Thymic Mucosa-Associated Lymphoid Tissue Lymphoma With Sjögren's Syndrome Revealed by CXCR4 Targeted 68Ga-Pentixafor PET/CT.

Mucosa-associated lymphoid tissue (MALT) lymphoma is an extranodal low-grade non-Hodgkin lymphoma that extremely rarely localises to the mediastinum. A 34-year-old female with chronic arthralgia, sicca and rash was found to have a well-demarcated mediastinal cystic mass with equivocal nodular enhancement within the cystic wall on chest CT during a workup for Sjögren's syndrome. Subsequent 68Ga-Pentixafor-PET/CT revealed focal uptake increase within the cystic capsule. The patient underwent thoracoscopic resection of the mediastinal lesion, and pathology revealed MALT lymphoma in the wall of a thymic cyst. This case highlights that 68Ga-pentixafor PET/CT could be valuable for the non-invasive detection of occult thymic MALT lymphoma. Trial Registration: ClinicalTrials.gov. (www.clinicaltrials.gov, NCT06086327).