Clinical History
A seven-year-old girl was admitted due to nausea, vomiting, one month of intermittent abdominal pain and distension. On physical examination, mild tenderness in the right upper quadrant was detected. CA125 level was significantly elevated.
Imaging Findings
Contrast-enhanced CT demonstrated a huge soft-tissue mass with heterogeneous density, clear and smooth border and intact capsule. The tumour was located on the entire right side of the abdomen without infiltration of surrounding visceral organs. The right lobe of the liver and right kidney were compressed by the mass and visibly deformed. At arterial phase, the tumour showed a non-homogeneous hypodense mass including variously enhanced scattered patches and an abundance of tortuous blood vessels. At portal and delayed phases, the degree and extent of enhancement of the tumour gradually increased. No enlarged lymph nodes or involvement of inferior vena cava were present.
Clinical history and imaging findings were strongly suggestive of retroperitoneal malignant sarcoma.
Postoperative pathology diagnosis was a retroperitoneal malignant fibrous histiocytoma.
Discussion
Malignant fibrous histiocytoma is the third most common retroperitoneal sarcoma (19%) [1]. Malignant fibrous histiocytoma is considered to arise from primitive mesenchymal elements and can occur in any part of the body. The tumour is the most common sarcoma appearing in late adult life (5th-6th decades) and men are more often affected than women (3:1) [1]. MFH is extremely rare in children and has an incidence of 2-7% of all soft tissue sarcomas [2]. MFH originates most commonly in the extremity followed by the retroperitoneum in adult age, in contrast to the head and neck regions in paediatric patients, and by the time of diagnosis has metastasized to the lungs in approximately 20% of cases [2, 3].
In imaging analysis, MFH usually presents a huge, mixed density and heterogeneously enhancing soft-tissue mass with necrotic areas, haemorrhage or with invasion of adjacent organs. Although CT and MR imaging appearances are nonspecific, some radiologic features may be helpful for the differential diagnosis [1, 4, 5].
The peripheral portions of the tumour often have variable patterns of calcification (7%–20% of cases), which may contribute to distinguish malignant fibrous histiocytoma from leiomyosarcoma [1]. In addition, myxoid variety of MFH and leiomyosarcomas are both moderately hypervascular tumours [5]. In our patient, we noticed an abundance of blood vessels inside the tumour and no intratumoral calcification. However, leiomyosarcomas tend to develop massive cystic degeneration and have central necrosis more commonly than other sarcomas [5]. Our patient’s tumour had large hypodense areas with no significant enhancement. Based on their density, shape, border and extent these areas were unlikely to be necrotic or cystic. Postoperative pathology showed a fish-flesh-like and jelly-like substance with necrotic areas and haemorrhage. CT findings also included significant enhancement of solid components, fibrous septa and tumour capsule on delayed scanning, which depended on the amount of fibrosis. At CT and MR imaging, neuroblastoma is irregular, lobulated, and heterogeneous and demonstrates coarse amorphous calcifications and variable contrast enhancement, as well as invasion of adjacent organs and encasement of vessels with luminal compression [1]. But in this case, the tumour had a clear border and intact capsule without involvement of surrounding organs and vessels, or regional lymph node metastases.
These features of imaging should be noticed when the radiologist is making an appropriate diagnostic opinion for the patient with a retroperitoneal mass.
Differential Diagnosis List
Malignant fibrous histiocytoma
Leiomyosarcoma
Neuroblastoma
Final Diagnosis
Malignant fibrous histiocytoma
