Possible causes of a firm mass in the stomach region include liver cancer, liver enlargement or renal cell carcinoma. The abdomen is divided into four major areas, and determining the area of the mass helps with diagnosing the exact cause, states MedlinePlus. All abdominal masses require medical examination.
Additional symptoms associated with liver cancer include abdominal discomfort, pain or tenderness, yellowing of the skin and eyes, and easy bruising or bleeding. The direct cause of liver cancer is unknown, as of 2015, according to Healthline. However, doctors have identified risk factors for cancer, which include aging, chronic infection with hepatitis, heavy alcohol consumption, cirrhosis and diabetes. Exposure to aflatoxin, a toxin produced by a mold that grows on peanuts, grains and corn, is also linked to an increased risk for liver cancer.
Causes of an enlarged liver include obesity, an infection, certain medications, alcohol consumption and certain types of hepatitis. Other causes are autoimmune diseases, metabolic syndrome, genetic disorders and abnormal growths, says WebMD. Problems with blood flow such as congestive heart failure and hepatic vein thrombosis are also linked to liver cancer. Other symptoms associated with an enlarged liver include feeling full, abdominal discomfort, jaundice, fatigue or weakness, and weight loss.