Cyclin A is a protein kinase to act a pivotal role in the mitotic phase of the cell cycle. The purpose of the current study was to elucidate the biological significance of immunohistochemical expression of cyclin A in superficial squamous cell carcinoma (SCC) of the esophagus. Immunohistochemical staining of cyclin A was performed for 45 samples of esophageal superficial SCCs. Clinicopathological features were compared between SCCs with and without cyclin A expression. Twenty-five superficial SCCs (55.6%) had positive expression of cyclin A and the other 20 (44.4%) did not. No significant difference regarding clinicopathological characteristics between esophageal SCCs with and without cyclin A expression. Infiltration of lymphocytes with germinal center cells was observed beneath 17 (68.0%) out of 25 superficial SCCs with cyclin A expression and 15 (75.0%) out of 20 superficial SCCs without cyclin A expression. Although 16 (94.1%) out of 17 superficial SCCs with cyclin A expression were associated with cyclin A expression in germinal center cells in infiltrated lymphoid follicles beneath the tumors, only 2 (13.3%) out of 15 superficial SCCs without cyclin A expression coexisted with cyclin A expression in lymphoid follicles beneath the tumors (P<0.0001). Cyclin A expression in the germinal center cells of the lymphoid follicles beneath the superficial SCCs of the esophagus might be an immunological signal toward the proliferation and progression of the tumors.
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