A detailed histological study on occult metastasis of the lymph nodes.

One representative microsection from each lymph node was carefully surveyed for metastasis in a routine examination. To scrutinize the existence of occult metastasis, three additional sections were then made from half of the remaining lymph node. A total of 1,698 lymph nodes taken from 55 patients with carcinoma of the esophagus, stomach, colon, thyroid or breast were thus reexamined histologically. The initial examination was not able to prove any metastasis in these lymph nodes. Upon reexamination, however, involvement by cancer cells was detected in 10 nodes of 7 patients. The maximum diameter of the metastatic foci varied from 0.2 mm to 1.3 mm and was less than 0.5 mm in more than half of the nodes. The metastatic patterns in the nodes were classified into three types, i.e., marginal sinus type, medullary sinus type and mixed type. The marginal sinus type was the most frequent, with the mixed type being next and the medullary sinus type being found in only one node. Accordingly, surgeons should keep the possibility of occult metastasis in mind and the marginal sinus of the lymph node should be carefully examined in order to detect any small foci of metastasis.