At the cellular level, what caused Sally's cancer

Uncontrollable cell division.

Explanation:

Cancer is a disease which is caused when cells division is uncontrollable and spread into surrounding cells and tissues. Mutations in genes is also responsible for the cause of cancer because this mutation accelerate the rate of cell division or inhibiting normal controls on the system, such as programmed cell death. When the mass of cancerous cells grows with the passage of time, it turn into a tumor.

loss of sensation to pressure and touch

the dorsal column–medial lemniscus pathway (dcml) (also known as the posterior column-medial lemniscus pathway (pcml)) is a sensory pathway of the central nervous system that conveys sensations of fine touch, vibration, two-point discrimination, and proprioception (position) from the skin and joints.