The pattern and timing of lymphatic metastasis of the rat carcinoma LMC.

The distribution pattern and latency of lymphatic metastases naturally disseminated by the Leeds Mammary Carcinoma (LMC1) when transplanted subcutaneously in isogeneic Johns' Strain Wistar rats has been determined. After the curative local irradiation and excision of the primary tumour in 210 rats, 55 +/- 3 per cent developed either local (26 +/- 3 per cent), and/or regional (28 +/- 3 per cent) and/or distant (37 +/- 3 per cent) lymph node metastases. Analysis of their pattern of distribution suggests that metastasis to local (inguinal and lumbar) and distant (axillary and mediastinal) nodes results mainly from the radial dissemination, trapping and nodal proliferation of cells released by the primary tumour. Although direct metastasis to the para-aortic node may have occurred, in the main seeding of this site and thence to other, regional, i.e. iliac and/or adrenal nodes, resulted from the dissemination of tumour cells from the local nodes. The latency of metastases appearing at different sites after primary tumour ablation, although highly variable, was site dependent and for local, regional and distant nodes was 30 +/- 14, 48 +/- 16, 56 +/- 17 days respectively. In addition, the latency of metastases at regional and distant nodes was directly correlated with the latency of local metastases. The latency of adrenal and iliac metastases also correlated with para-aortic node metastasis, as did mediastinal with axillary lymph node metastasis. From the data, a semi-quantitative model of lymphatic metastasis has been developed for further evaluation and adjuvant chemotherapy testing.