Small cell carcinoma of prostate associated with myasthenic (Eaton-Lambert) syndrome.

A fifty-eight-year-old white man was diagnosed as having an adenocarcinoma of the prostate (grade III by the U.T.M.D. Anderson Hospital grading system). Five years after the initial diagnosis and three months after signs and symptoms of the myasthenic syndrome of Eaton-Lambert (MSEL), he was found to have a small cell carcinoma of the prostate. Histologic examination showed adenocarcinoma merging into a small cell carcinoma component of intermediate cell type. Immunostaining was positive for neuroendocrine markers--namely, neuron-specific enolase and serotonin--and was limited to the small cell carcinoma component. This is the first report of a patient with small cell carcinoma of the prostate presenting with MSEL. Our findings support prior observations of a strong propensity for small cell carcinoma to be associated with paraneoplastic syndromes, regardless of the initial location of the tumor.