 [ Symptoms ] my 23 yo son developed a 2 inch lump at the base of the skull just above the hairline the lump is tender and red and directly in the center of his head where the spine ends [ Disease ] no medical professional could make an accurate assessmentdiagnosis based solely on a vague description your son needs to have this lump carefully examined by a medical professional it could be many different things a sebaceous cyst a reactive post occipital lymph node or please encourage him to do the right thing and have it properly examined and diagnosed