Introduction
Solitary fibrous tumour, are uncommon mesenchymal neoplasms that are anatomically ubiquitous and occur most often in middle aged adults aged 20-70 years, with cases in children and adolescents being rare. Males and female are equally affected. Solitary fibrous tumours may be found at any location; 40% in the subcutaneous tissue, while others arise in deep soft tissue of extremities or in the head and neck region (especially the orbit), thoracic wall, mediastinum, pericardium, retroperitoneum, and abdominal cavity. Other locations described include meninges, spinal cord, salivary gland, lung, thyroid, liver the gastrointestinal tract, adrenal, kidney, urinary bladder, prostate, spermatic cord, testis, bone and skin.
Although most cases are benign, the behavior of solitary fibrous tumour can be unpredictable. About 10% behave aggressively, and local or distant recurrence can occur many years after primary resection. Lesions located in the mediastinum, abdomen, pelvis, retroperitoneum and/or meninges also tend to behave more aggressively than those in the limbs. Although there is no strict correlation between morphology and behavior, malignant histology (especially high mitotic counts) remains the best indicator of poor outcome; most (but not all) histologically benign solitary fibrous tumours prove to be non-recurring and non-metastasizing lesions,and most histologically malignant tumours behave aggressively.
In this report we describe the clinical aspect, histopathological, immunohistochemical and next generation sequencing findings of a malignant solitary fibrous tumour of the retroperitoneum.