抄録
The first case in Japan of ectopic solid thymus gland of the neck in a 2-month-old boy is presented. Reports of cases of ectopic thymic tissue or thymoma in Japan are reviewed. According to Patten’s Human Embryology, the thymic primordia in man appear late in the sixth week of gestation as ventral out-growths of the third pharyngeal pouches. By the early part of the seventh week, the primordia have considerably elongated but are still connected with the pharyngeal pouches and remain associated with the pair of parathyroid glands derived from the third pharyngeal pouches. During the seventh week, they increase rapidly in mass and their distal tips begin to approach each other as they swing toward the midline just caudal to the thyroid primordium. By the middle of the eighth week the distal tips of the thymic primordia have made contact with each other and have started to descend under the sternum into the mediastinum where they lie in contact with the parietal pericardium. At any portion along this path of descent the entire gland or portions thereof may be left behind. Glimour 1), in 1941, reported 13 cases showing thymic tissue of unusual portions. Eleven of these were infants. In one there was unilateral hyperplasia with complete absence of descent from the neck. Since Hyde et al. reported, in 1944, the removal of a cystic thymus gland weighing 36g from the right side of the neck, 46 cases of incompletely descended ectopic thymus tissue in the neck have been documented in the English medical literature as described by Hinds et al.2) Because of the rare occurrence of solid ectopic thymus gland of the neck, it was felt that the first case in Japan should be added to world medical literature.
