A 50-yrs-old woman is diagnosed with cervical cancer. Which lymph node group would be the first involved in metastatic spread of this disease beyond the cervix and uterus?

The cervix and upper vagina drain laterally to the parametrial, obturator, and external iliac nodes and posteriorly along the uterosacral ligaments to the sacral nodes. Drainage from these primary lymph node groups is upward along the infundibulopelvic ligament, similar to drainage of the ovary and fallopian tubes to the para-aoic nodes. The obturator is frequently the first 'Major'group of lymph nodes which is also called the sentinel group for ca cervix.