Conversation: The conversation between human and AI assistant.
[|Human|] I have a lump on the back of my neck at the base of my skull.  It is about the size of an egg yolk.  It is not really painful, except that it doesnt feel comfortable when pressure is applied.  The lump has been there for at least 5 years.  No real complaints, just very concerned.  What could it be?  Should I be worried?  Do I need to have an MRI or anything?
[|AI|]  Hello! Welcome to Chat Doctor. Yes, your concern is very true. This can be a lipoma or sebaceous cyst. Local examination for diagnosis is necessary. If soft, freely mobile suggests lipoma, if puncture (black dot) is present, its sebaceous cyst. Many times FNAC - fine needle aspiration cytology is advised for accurate diagnosis. Treatment is usually excision, if symptomatic. Hope this information is useful for you. Wish you healthy life. Thanks. Regards.