Age Changes in the Human Palatine Tonsils, with Remarks on the Histology of the Secondary Nodules

Abstract

In connection with a study of the aging process in thymolymphatic tissues (AWAYA and ODA 1965), it became disirable to have knowledge of the age changes in the human palatine tonsils. The purpose of the present study is to examine this subject.
Eighty palatine tonsils with relatively slight or without any noteworthy lesions in the histopathological features, chosen from 165 patients performed on tonsillectomy under the diagnosis of the enlarged tonsil or chronic tonsillitis clinically, were used as material. They were divided into 8 groups by age: 4 to 5, 6 to 10, 11 to 15, 16 to 20, 21 to 25, 26 to 30, 31 to 40, and 41 to 49 years. Serial cross-sectional cuts, 6μ in thickness, were made from these tonsils after fixing in Zenker-formol and embedding in paraffin. The sections were stained with Meyer's acid hemalum and eosin.
In this study, special attention was directed to the changes in the number and the percentage of the area of the secondary nodules in the organ. After measuring the area of the sections, the number of secondary nodules of different types occurring per 1cm² of section was determined. As the author was able to confirm that in one extensively studied case the secondary nodules are distributed with great uniformity throughout the tonsil, the counting of the number of the secondary nodules was made of only 1 or 2 sections from each case. This method also provides for obtaining the percentage of the area of the secondary nodules. The secondary nodules of the Flemming types were classified into 3 types according to the cellular component consisting of the pale staining-center: (1) active, (2) half-active, and (3) inactive mature secondary nodules. If the pale centers are almost entirely composed of densely packed, medium-sized lymphocytes with many mitotic figures, they are termed “active”; otherwise they are called either “half-active” or “inactive”. The center of “inactive” type is composed mainly of reticular cells and devoid of mitotic figures of lymphocytes (Figs. 4-9).
The main findings are shown in Tables 1 and 2, and Figures 1 to 3.
The number of secondary nodules per unit area reached a maximum in the 16-20 age group, but the maximum numbers of the active and half-active forms, characterized by the active proliferations of lymphocytes, were attained in the 6 to 10 age group. The percentage of the area of the secondary nodules also reached in a maximum in the 4 to 10 age groups. As seen in Figures 1 and 2, the curve of the numbers of active and half-active forms then dropped sharply in the 11 to 1.5 age group and kept on at a low level during the succeeding periods studied. On the other hand, the curve of the number of the total secondary nodules including the non-active form and the percentage of their area showed a temporary fall in the 11 to 15 age group, the values again rising close to the maximum level in the 16 to 20 age group: thereafter the curves fell off markedly with increasing age.
In addition, the amount of the lymphatic tissues other than the secondary nodules in this organ was observed to be largest in the 4 to 10 age groups and the number of lymphocytes appearing in the epithelium of the tonsils also largest in this period. These show that there is found some parallelism between the postnatal development and involution of the total tonsillar tissues and the aging process of the secondary nodules herein.
Thus, the human palatine tonsils reach their maximal growth in the 4 to 10 age groups and thereafter undergo a slight involution which continues till about 20 years of age; beyond this age, this is followed by a more advanced involution. It is suggested that 11 and 21 years of age are the two critical times in the aging process of human palatine tonsils.