GM1 is a member of the ganglio series of gangliosides which contain one sialic acid residue. GM1 has important physiological properties, and impacts neuronal plasticity, repair mechanisms, and the release of neurotrophins in the brain. The fucosylated form of GM1, Fucosyl GM1, with 2-hydroxy fatty acids as a characteristic component of the ceramide, has been described as frequently and differentially expressed in small cell lung carcinoma (SCLC). SCLC cases (ranging from 58-90%) have been reported to express Fucosyl GM1, while up to 20% of squamous and large cell non-small cell lung cancer (NSCLC) cases have demonstrated expression. Expression has not been identified in lung adenocarcinoma, bronchial carcinoid, and neuroblastoma. Small amounts of Fucosyl GM1 without 2-hydroxy fatty acids were detected in normal adult pancreas, spleen, and brain but could not be detected in normal lung tissue. By immunofluorescence, most normal tissues were negative, although in thymus, spleen, and lamina propria of the small intestine, sparsely distributed clusters of small round cells were stained as well as intramural ganglionic cells of the small intestine and islet cells of the pancreas.