Abstract
Objective: The palatine tonsil contains innate immune cells such as natural killer (NK) cells and macrophages. Tonsillar cancers often present locally early tumors with cervical metastases. This study was performed to clarify the possibility that the growth of primary tumors might be inhibited by innate immune cells in the palatine tonsil.
Method: NK cells and macrophages were immunohistochemically identified using anti-HNK-1 and anti-CD68 antibodies. The degree of the immune cell infiltration in tonsillar cancers, tongue cancers, and normal tonsils was estimated by counting the number of NK cells and macrophages in formalin-fixed, paraffin-embedded blocks. Phagocytosis of the tumor cells was also studied.
Results: There was a significant increase in the number of NK cells in locally early tonsillar cancers (a median of 100 in 8 patients) in comparison to locally early tongue cancers (a median of 8 in 15 patients) and 5 normal tonsils (a median of 35; P < .0001). The number of macrophages was also significantly increased in tonsillar cancers (a median of 247) in comparison to tongue cancers (a median of 81) and normal tonsils (a median of 82; P < .0001). Phagocytosis of tumor cells by macrophages was observed significantly more frequently in tonsillar cancers than in tongue cancers (P < .01).
Conclusion: The innate immune reactions were observed to significantly increase and they might therefore inhibit the growth of the primary tumor in locally early tonsillar cancer. In addition, these inhibitory immune reactions against the primary tumor in the palatine tonsil might be part of the etiology of developing primary-unknown cervical metastasis.
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