Intra-abdominal spindle cell lesions: a review and practical aids to diagnosis

Intra-abdominal spindle cell lesions are uncommon and often present a diagn ostic challenge. An important group of such lesions are the gastrointestina l stromal tumours. Other intra-abdominal spindle cell lesions include fibro matosis, various sarcomas-in particular, leiomyosarcoma, liposarcoma. and m alignant peripheral nerve sheath tumour-and, in women, endometrial stromal sarcoma. Less common lesions are inflammatory myofibroblastic tumours, the mesenteric spindle cell reactive lesions, retroperitoneal fibrosis, and sol itary fibrous tumour. A variety of intra-abdominal tumours of nonmesenchyma l origin spindle cell/sarcomatoid morphology; these include sarcomatoid car cinoma, malignant melanoma and, in women, sarcomatoid granulosa cell tumour . Finally, metastatic sarcomas from pelvic or extra-abdominal organs need a lso be considered. A set of practical aids to the diagnosis of intra-abdomi nal spindle cell lesions is presented to assist pathologists dealing with s uch lesions, particularly with regards to the consideration of differential diagnoses.