Current evidence on diagnosis and treatment of parotid gland lymphomas: a systematic review

Background and purpose: Parotid gland lymphoma (PGL) is a rare and challenging diagnosis. Different lymphomas can develop in the parotid gland, with the most common being the mucosa-associated lymphoid tissue (MALT) lymphoma, which originates directly from the glandular parenchyma. Other histologic subtypes arise from both intraglandular and extraglandular parotid lymph nodes. A consensus on diagnosis and treatment of PGL is still lacking, and published data is scarce and heterogeneous. Methods: We performed a systematic review of the literature, including studies published after 2001, when the WHO classification of lymphoid tumours was introduced. Results: Twenty retrospective studies were included in the analyses, eight of which focused exclusively on MALT lymphomas. Final analysis included 612 cases of PGL, with a 1.68:1 F/M ratio. MALT lymphoma was the most common histology, followed by follicular and diffuse large B-cell lymphoma. Most cases were low stages (IE/IIE acc. Ann Arbour, 76.5%) and only 10% of patients presented with symptoms, most commonly pain (4.8%) and B symptoms (2.2%). A high prevalence of associated autoimmune diseases was found, particularly Sjögren's syndrome, that affected up to 70% of patients with MALT lymphoma. In most cases diagnosis was achieved through parotidectomy (57.5%), or open biopsy (31.2%). Treatment strategies were either surgical, non-surgical or a combination of modalities. Surgery as a single-modality treatment was reported in about 20% of patients, supposing it might be a valuable option for selected patients. Conclusions: Our review showed that the diagnosis and treatment of PGLs is far from being standardized and needs further, more homogeneous reports to reach consensus.