A male patient, aged over 75 years, was referred to the emergency room for pain in his right hypochondrium. This pain, which persisted for approximately 3 days, radiated to his right flank and right iliac quadrant and worsened after meals. The patient reported no nausea, vomiting, diarrhoea, fever or recent traumatic events. Blood laboratory tests, ultrasonography, an MRI and a CT scan were performed, leading to the diagnosis of a mass in the Morrison’s pouch with ultrasound features of adipose tissue compatible with a liposarcoma, infiltrating the liver and the right kidney. Subsequent CT-guided needle aspiration and a histological examination led to the diagnosis of actinomycosis. The patient was initially treated with a daily dose of 18 million IU of benzylpenicillin for 4 weeks and subsequently prescribed the oral administration of 3 g/day of amoxicillin for 11 months. A monitoring CT scan was performed after 1, 5, 8 and 12 months, and a CT scan re-evaluation confirmed that the mass had completely healed.
