Reproduction of occult metastasis of head and neck cancer in nude mice.

The presence of occult metastasis is the most important factor that influences the prognosis in patients with head and neck cancer. To reproduce occult metastasis of oral cancer cells, we serially resected the primary focus in an orthotopic implantation model to examine when metastasis of cancer cells occurs. Human squamous cell carcinoma was implanted into the tongue of nude mice divided into two groups, non-surgery and surgery groups. Mice in the non-surgery group were sacrificed, and the tongue cancer and cervical lymph nodes were resected simultaneously. In the surgery-group, resection of the tongue cancer was performed, and the cervical lymph nodes were resected on day 28. For the non-surgery-group, the incidences of metastasis were 0%, 9%, 36%, 91% and 100% on days 3, 7, 14, 21 and 28, respectively. For the surgery-group, resection of the tongue cancer was performed on days 3, 7 and 14, and the incidence of metastasis on day 28 was 0%, 82% and 91%, respectively. The occult metastasis was reproduced using resected primary cancer on day 7. This time-based model may be useful to clarify the mechanism of metastasis and to develop new treatments.