Metastasis of prostate tumor cells to bronchus associated lymphoid tissue

We investigated the metastatic process to the lungs from subcutaneous transplants of R3327-MatLyLu tumor, a rat model for anaplastic prostatic carcinoma. Considerable metastasis of tumor cells to bronchus associated lymphoid tissue (BALT) was observed with time. Immunocytochemistry clearly showed the presence of the epithelial type of intermediate filaments (cytokeratin) in these cells, confirming their carcinomatous origin. No positive staining for cytokeratin could be observed in the BALT in controls. Localization of tumor cells within the BALT was mainly confined to the region near the adjacent artery. After intravenous injection of monodispersed tumor cells, an influx of tumor cells was observed within minutes in this same region of the BALT. These observations suggest that BALT is involved in the metastatic process of tumor cells to the lungs. Its role in controlling metastasis and in tumor cell kill, if any, remains to be elucidated.