Hi, happy to help you on your health concern on part of HCM! In the present case of subcostal swelling or lump, if I were your consulting physician, I would just consider a possibility of hernia before anything else and would suggest USG of the region for confirmation! However, as per your description, it could be some other lump like lipoma, neurofibroma, cyst, dermatofibroma or even lymph node! Therefore try to avoid constipation and straining while defecation and reduce weight... If you are still worried, please get examined by a surgeon or get some FNAC like cytological examination or revert back to us. Hope you got your answer. Please feel free to write to us if any more queries. Wishing you the best health!