Gastrointestinal autonomic nerve tumours: a report of nine cases.

We describe the clinicopathological features of gastrointestinal autonomic nerve tumours in nine patients where the diagnosis was confirmed by electronmicroscopy. Most patients presented with abdominal pain. At laparotomy, large intra-abdominal tumour masses were found which tended to be cystic and haemorrhagic. The predominant histological patterns were nests, sheets and fascicles of spindle and epithelioid cells. Immunohistochemistry showed positive staining for neuron specific enolase (9/9), PGP 9.5 (9/9), NKI/C3 (7/9), vimentin (7/9), alpha-smooth muscle actin (5/9), vasoactive intestinal peptide (3/9) and CD34/QBend10 (2/9). Grimelius staining was positive in two of nine cases. All tumours were negative for CAM 5.2, chromogranin, synaptophysin, Leu 7, neurofilament protein, muscle-specific actin (HHF-35) and desmin (D33). Ultrastructural examination showed cellular processes and dense-core granules in all cases. Three tumours had microtubules and/or intermediate filaments, particularly in cell processes. Skeinoid fibres were seen in three cases. No convincing synapses or small (synaptic-type) vesicles were identified. There was no evidence of epithelial, smooth muscle or nerve sheath differentiation. Two patients died due to tumour, two died of unknown causes and the remainder are alive 2-44 months after presentation. Four of the five survivors have recurrent/residual intra-abdominal tumour. So-called gastrointestinal autonomic nerve tumours are apparently slow-growing malignant tumours showing neuronal differentiation. Four cases arose in the mesentery/retroperitoneum or omentum rather than bowel wall and therefore a more appropriate nomenclature might be intra-abdominal stromal tumour with neuronal differentiation.