Primary retroperitoneal neoplasms are an extremely rare group of tumours (lymphoma is not included in this definition). The most common type is soft tissue sarcoma (90%).
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Epidemiology
The most common age for presentation is 40-50 years.
Clinical presentation
Frequently tumours have relatively unimpeded growth where symptoms develop late and the tumour at presentation tending to be extremely large (average size 11-20 cm).
Pathology
Primary retroperitoneal neoplasms arise from outside the major organs, and are divided according to histological types:
- mesenchymal origin: skeletal muscle, fat, peripheral nerve, vessels, fibrous tissue
- extragonadal germ cell tumours
- primary retroperitoneal adenocarcinoma
Aetiology
The order of frequency of primary retroperitoneal malignancy is as follows:
- liposarcoma
- undifferentiated pleomorphic sarcoma
- leiomyosarcoma
- rhabdomyosarcoma
- fibrosarcoma
- malignant peripheral nerve sheath tumour
- solitary fibrous tumour
- extragonadal germ cell tumour
- primary retroperitoneal adenocarcinoma
Causes include radiotherapy, e.g. neuroblastoma treatment as a child.
Radiographic features
Imaging is used to confirm the diagnosis, assess for any metastatic disease and determine the potential for resection. CT is the most commonly used tool. MRI can be used for further differentiation, but histology is always required.
Percutaneous biopsy may be undertaken (after consultation with surgeons and oncologists), and for assessment of tumour grade, PET may be used 2.
Treatment and prognosis
Prognosis depends on the histological type of a tumour and the potential for resection.
Recurrence rates are high (90% in some series), so imaging surveillance is an important part of continued follow-up.