Autoimmune impairment and destruction of the enteric nervous plexus are thought to play a central role in the pathogenesis of paraneoplastic motility disorders. We present a case of a small-cell lung carcinoma-related paraneoplastic motility disorder associated with abnormal interstitial cells of Cajal networks. Antibodies against c-Kit and protein gene product 9.5 were used to selectively stain interstitial cells of Cajal and the enteric nervous plexus, respectively. A 68-yr-old man presented with anorexia, early satiety, nausea, and weight loss. Investigations revealed gastroparesis, delayed small intestinal transit, and mediastinal lymphadenopathy. The patient was seropositive for type 1 antineuronal nuclear autoantibody and P/Q-type calcium channel antibody. Biopsy of mediastinal lymph nodes revealed metastatic small-cell carcinoma cells that were immunoreactive for c-Kit. Immunohistochemical staining of a full-thickness small intestinal biopsy revealed a relatively intact myenteric plexus but a sparse and disorganized interstitial cells of Cajal network. The histopathology of this case suggests that interstitial cells of Cajal may be a target in the pathogenesis of paraneoplastic motility disorders.
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