Prognostic impact of HLA class I immunohistochemistry staining intensity with regard to the risk of recurrence of adenoid cystic carcinoma

Adenoid cystic carcinoma (AdCC) evolves from the salivary glands and may arise in the head and neck region or outside of this area. The symptoms of AdCC are generally nonspecific, and its diagnosis is challenging due to its heterogeneous histopathology and indolent growth. Moreover, reliable prognostic markers are lacking. Therefore, the present study investigated the prognostic potential of immunohistochemical staining of the immune markers HLA class I, CD4, CD8 and FOXP3 in AdCC. In total, 72 patients diagnosed with AdCC between January 2000, and December 2014 were included. Biopsy material underwent immunohistochemical staining for the aforementioned markers, and staining extent and intensity in the tumour and corresponding stroma were assessed, and their association with clinical outcome was investigated. Patients with analogous staining intensity of HLA class I in the tumour tissue to that in the stromal tissue had significantly fewer recurrences, as compared with those with lower HLA class I intensity staining in the tumour than in the stroma. By contrast, CD8+, CD4+ and FOXP3+ staining was not significantly associated with recurrence. Furthermore, none of the markers were associated with overall survival. Moreover, patients with clinical stage I and II had fewer recurrences than those with stage III and IV AdCC. In conclusion, among the investigated biomarkers, only an analogous HLA class I expression in tumour tissue relative to that in the stromal tissue was associated with a reduced risk of recurrence in AdCC. These findings suggest a potential role of HLA class I as a prognostic marker in this rare malignancy.