hi, thank you for your query. seromas are common after abdominal and neck surgeries as fluid easily piles out from these areas. The fluid, called serum, leaks out of nearby damaged blood and lymphatic vessels. surgery to correct 5 hernias is a major procedure hence chance for large seroma formation are more. Small seromas often resolve on their own, although left untreated, they can calcify, forming hard knots. Larger seromas often require aspiration with a needle. Seromas that become infected may require antibiotic therapy and very rarely surgery hence the mass you are complaining of can be- 1.just an increase in the size of seroma 2.calcification of the seroma 3.infection of the seroma in either case i would suggest a thorough physical checkup by your surgeon to pinpoint the cause and plan appropriate treatment. thank you, you can refer to me for any further questions