Micrometastases to the axilla in breast cancer: their size and season of presentation.

In a series of 1,069 breast cancer patients there were no significant differences in the numbers of node-negative or node-positive cases undergoing operation in the two halves of the year. This held also for cases with nodal micrometastases (0.2 cm2 or less). There were two histological types. Their distribution according to season was similar. Using the mean tumour area those presenting in the first half of the year were smaller than the others (p < 0.001), and more cases were under 0.000 cm2 (p < 0.005). In these cases the tumour cells tended to be in the capsular lymphatics and subcapsular sinus. In keeping with their histology, deaths were also more frequent than with those presenting in the second half of the year, in which the micrometastases were larger and had usually infiltrated the nodal lymphoid tissue. Thus the metastatic process in the primary appears to be active in the first part of the year when the smallest of the micrometastases are found entering the nodes. This may be a reflection of the growth form of the primary.