Spontaneous regression of cervical lymph node metastasis in a patient with mesopharyngeal squamous cell carcinoma of the tongue: possible association between apoptosis and tumor regression

Background. We report a case of mesopharyngeal squamous cell carcinoma with spontaneous regression of lymph node metastasis. Spontaneous regression of lymph node metastasis of head and neck carcinoma has not been reported previously. Possible causes of the regression of lymph node metastasis include regression of lymphocytic division transiently inflated by an immunological stimulus, and en-bloc tumor necrosis due to degradation of vascularity, such as thromboembolism and intranodal hemorrhage. However, the patient's history and repeated imaging analyses suggested that these factors were not responsible for the regression. To clarify the etiology of this rare phenomenon, we investigated the cause of spontaneous regression with analyses of paraffin-embedded sections. Methods. The frequency of cystic lesions, en-bloc necrotic lesions, and apoptosis of carcinoma were investigated with immunohistochemical analysis, and these features were compared with those in specimens from five other patients with head and neck squamous cell carcinoma. Results. The present case revealed no tendency towards microscopically confirmed cystic formation or necrosis, but the frequency of apoptosis was significantly higher than that in the other five cases. The apoptotic tendency was not restricted to the lymph node in which spontaneous regression was confirmed clinically, but was also consistently observed in other lymph nodes and in the primary lesion that was detected and radically ablated 2 months after complete neck regional dissection had been done. Conclusion. Our case may be the first case of squamous cell carcinoma undergoing spontaneous regression in which enhanced apoptosis was demonstrated quantitatively. The findings were considered to contribute to evidence of spontaneous regression in squamous cell carcinoma of the head and neck resulting from enhanced apoptosis.