The roots of all palms are adventitious in origin. What that means is that instead of the more familiar formation of roots under the plant in the soil they originate from stem tissue or old woody roots of the plant.
Below, what looks like some sort of cancerous growth near the bottom of this Queen Palm (Syagrus romanzoffiana – more about this palm at http://floridagardener.com/pom/queenpalm.htm) is the normal initiation of roots from the base of the palm trunk in an area called the root initiation zone. This area starts in the center bottom of the stem in palm seedlings. As the palm grows, the root initiation zone expands outward and upward, eventually working its way up along the base of the palm’s trunk. Where these root initials are in contact with the soil or other moist environment, they will continue their development, growing out and down into the soil as typical functioning roots.
Root initials that arise from above-ground portions of the root initiation zone typically are exposed to a drier environment and their growth and development are delayed until their environment becomes moist enough to support their growth (for example, you may notice new growth during the rainy season). Typically the visible aerial portion of the root initiation zone on most palms extends up the trunk no more than six to 12 inches.
As the root initiation zone on older palms expands up above the soil line, these new root initials, which arise from tissue under the "bark" (cortex) of the palm trunk, eventually split the "bark" and force it outward in a flared fashion. This is a normal part of development as a palm matures, but the degree to which this "bark" flares out varies among palms.