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1.The history and symptoms suggest most possible cause could be Sebaceous
cyst - which does not need any specific treatment unless until causing discomfort or cosmetic issues.
2.Next possible cause could be
lymph nodal enlargement - but does not expect to see for so long with no change.
3.In this case i would recommend to get a
ultrasound scan done- that will characterise the lesion ( cystic / solid / mixed ) and its source and extensions.
4.In case of mass lesion an FNAC - fine needle aspiration cytology would help to evaluate the nature of cells.
5.Suggest to get an appointment with your GP, get examined and needful investigations and treatment will help. Good luck.
Hope i have answered your query.
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http://doctor.healthcaremagic.com/doctors/dr-ganesh/62888 Thank you.