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1. The lump with tender on touch and semi firm - features suggest as an infective lump, bacterial infection and collection of fluid within. in this case a course of antibiotic after a small
incision and drainage will help.
2.Most possible cause of lumps on the ankle are ganglions - which normally arising from the tendon, ligaments - in a sports and active movements and trauma.
3.To get clarify what it is - get an appointment with GP and let it get examined, after that an
ultrasound lesion get done - to evaluate the nature of the lesion, its source and its extensions.
4.In case of solid mass an FNAC - fine needle aspiration cytology can be done to evaluate the nature of cells.
5.If any possibility
MRI will be the best investigation in relation with tendons, ligament and joint space.
Hope it helps you. Wish you a good health.
Anything to ask ? do not hesitate. Thank you.