The subject invention provides a method for detecting the presence of human malignant cells in a sample of tumor cells, which comprises contacting the sample with an antibody directed to an epitope present on the .beta. subunit of human luteinizing hormone or on intact human luteinizing hormone under conditions such that the antibody forms a complex with cells present in the sample if the epitope is present on the surface of the cells, and determining whether the antibody forms such a complex. The subject invention also provides a method for determining whether a tumor present in a human subject is malignant which comprises obtaining a sample of cells from the tumor and detecting the presence of malignant cells in the sample according to the method of the subject invention. Finally, the subject invention provides a method for obtaining an enriched population of live human malignant cells which comprises contacting a population of cells comprising live human malignant cells with an antibody directed to an epitope present on the B subunit of human luteinizing hormone or on intact human luteinizing hormone under conditions such that the antibody forms a complex with the cells present in the population if the epitope is present on the surface of the cells, and isolating the cells which form a complex with the antibody.