LTE uses two different radio links for downlink and uplink, that is, from tower to device, and vice versa. For the downlink, LTE uses an OFDMA (orthogonal frequency division multiple access), which requires MIMO.
What you are referring to is called plaque, and it's a hallmark of atherosclerosis or arteriosclerosis (they both mean the same thing). Basically, cholesterol deposits end up lining the interior walls (lumen, intima) of the arteries narrowing the opening.
First of all, tumours (that is, abnormal cellular growth) of blood vessels are extremely rare. What you are referring to is called plaque, and it's a hallmark of atherosclerosis or arteriosclerosis (they both mean the same thing). Basically, cholesterol deposits end up lining the interior walls (lumen, intima) of the arteries narrowing the opening. Then a clot could come along and block the arterial opening or the plaque could rupture, occluding the vessel and killing off cells downstream. Very bad if those cells are in the heart or brain.