[Clinicopathological features and possible prognostic factors in parotid lymphomas]

Objective: To investigate the clinicopathological features and prognostic factors in lymphoma of parotid origin.

Methods: Clinicopathological data of the patients with parotid lymphoma who were initially diagnosed in Peking University Hospital of Stomatology from 2006 to 2016 were collected and analyzed retrospectively. The patients were followed-up for 5 to 149 months with a median period of 45 months, and the factors influencing the prognosis were evaluated.

Results: A total of 41 patients with primary parotid lymphoma were included in this retrospective study. The rate of male to female was 1:2.15. The median age was 57 years (ranging from 8 months to 91 years). According to WHO classification, 40 cases (97.1%) were diagnosed as non-Hodgkin lymphoma (NHL), including 15 cases of extranodal marginal zone B-cell lymphoma of mucosa-associated lymphoid tissue (MALT), 14 cases of diffuse large B cell lymphoma (DLBCL) as well as 4 cases of follicular lymphoma, while other subtypes of NHL were rare. Only one case was diagnosed as Hodgkin lymphoma. Regarding the clinical staging at the initial diagnosis, 37 patients (90.2%) were diagnosed as stage IE or IIE of the disease, while 4 patients (9.8%) as stage IIIE or stage IVE. Seven patients (17.1%) had a history of Sjögren syndrome (SS), all of whom were MALT lymphoma. The mean ill duration of the 41 patients were 20.7 months. Thirty-two patients (78%) presented a slowly growing painless mass in the parotid gland. Treatment options included localized therapy and systemic therapy, all of whom had good curative effect. Nine patients (21.9%) died during the follow-up period. The overall survival rates of 2-year and 5-year were 84.5% and 81.3% respectively. The univariate analysis demonstrated statistically significant differences for accelerated growth of tumor (P=0.005), and presence of tumor capsule (P=0.011). The multi-univariate analysis demonstrated statistically significant differences for presence of tumor capsule (P=0.041).

Conclusion: A large majority of primary parotid lymphoma were NHL, among which MALT lymphoma and DLBCL were common subtypes. Most patients presented an indolent mass in parotid gland, which should be distinguished from the parotid benign tumors. SS is closely related to the pathogenesis of MALT lymphoma. The prognosis is better than that of other malignant parotid tumors. Absence of tumor capsule may predict a poor prognosis in patients with parotid lymphoma.