SCC tumor on scalp treatm. Also treated?

My mother has a small bump of 2 cm on scalp from 10 years. From last Feb we noticed sudden growth in size. Consulted neuro surgeon and operated as diagnosed lifoma. After 2 months we notice again small bump araises in same location. Then we enquired for biopsy result. It is shown SCC. Then same operated with oncologist with adjuvant radiotherapy. It that time margins clear and informed treatment working well. During that time small 2.5 mm nodules identified in lung with pet scan. Doctors told no need to see now it needs follow up. After 3 months now with CT scan multiple lesions noticed in lung with max size 40 X 35 mm. 20X15 mm near spinal . What does this means. What gone worng with us. 1. Earlier cancer not identified in any test during first operation. 2. During second operation and radiotherapy lung nodule also treated? Now I want to know what is next action to be taken and what stage of cancer is this. Please inform me .