Simultaneous MALT lymphoma of the thymus and parotid gland. Independent lymphomas or metastatic spread?

Background: Mucosa associated lymphoid tissue (MALT) lymphoma of the thymus is rare and generally associated with autoimmune disorders. It is generally suspected in middle-aged asian women with Sjogren’s syndrome or other autoimmune diseases presenting a multicystic mediastinal mass. Contrary to other MALT lymphomas, the etiology of these tumors is still uncertain especially those affecting patients with no autoimmune diseases. Thymic MALT lymphoma with simultaneous salivary gland involvement is extremely rare, with only few cases described in literature. Case presentation: We present a case of a 33 years-old male, with a recent history of MALT lymphoma of right parotid gland, affected by thymic mass. The patient underwent a right video-assisted thoracoscopy with radical thymectomy. The histological examination revealed a MALT lymphoma of the thymus. The molecular analysis on both thymic and parotid MALT lymphoma for clonal rearrangement of the immunoglobulin heavy chain gene suggests the origin from the same lymphomatous clone. Conclusions: It is still unclear if multiple localizations of MALT lymphomas are attributable to the development of different primary lymphomas or can be caused by lymphatic metastatic spread. Our analysis reveal that the hypothesis of metastatic spread cannot be excluded in patients with simultaneous MALT lymphoma of the thymus and parotid gland, especially in non-autoimmune related MALT lymphomas.