Methods and kits for detecting alternating spatial expression of PTEN and, optionally, SMAD4, CD44, and/or TP53 in colonic tumors are described. The methods and kits are useful for identifying a cancer stem cell (CSC)-like zone within a colonic tumor, identifying an adenoma-adenocarcinoma (Ad-ACA) transition zone in a colorectal cancer (CRC) tumor, identifying a CRC tumor that contains high-grade adenoma and/or early adenocarcinoma regions, identifying CSCs in a CRC tumor, diagnosing a subject with high-grade colon adenoma and/or early adenocarcinoma, and determining the likelihood that a colonic tumor in a subject will undergo invasive transformation if left untreated.