Identification of tumors and tissues

A method of classifying a cell containing sample as containing tumor cells of a type of tissue, said method comprising

• determining the expression levels of about five to 49 transcribed sequences from cells in a cell containing sample obtained from a human subject, and
• classifying the sample as containing tumor cells of a type of tissue from a plurality of tumor types based on the expression levels of said sequences,
• wherein the ratio, of transcribed sequences to the number of tumor types, used in said classifying is from about 1:2 to about 5:2 or higher, and
• wherein a) the expression of more than 50% of said transcribes sequences are not correlated with expression of another one of said transcribed sequences, or
• b) the five to 49 transcribes sequences are not selected based upon supervised learning using known tumor samples, on the level of correlation between their expression and said plurality of tumor types, or on their rank in a correlation between their expression and said plurality of tumor types.