Polycystic tumor of the atrioventricular nodal region in a man with Emery-Dreifuss muscular dystrophy.

Benign polycystic tumor of the atrioventricular nodal region is a lesion associated with cardiac conduction defects with atrioventricular block and sudden death. We present the clinical and light microscopical, immunohistochemical and ultrastructural findings of such a lesion in a young man with X-linked recessive Emery-Dreifuss muscular dystrophy who died suddenly. The tumor has not previously been described in this group of patients, who frequently suffers from cardiac electric instability and sudden death. Possible mechanisms by which the tumor may cause arrhythmia are discussed and the presence of neuroendocrine cells in the lesion is emphasized.