Here we describe a unique case of isolated thrombocytosis as an initial presentation of CML in a 21-year-old woman, where the BCR-ABL1 fusion gene was detected in bone marrow (BM) aspiration and biopsy specimen after a negative peripheral blood (PB) fluorescence in situ hybridization testing. Here, BCR is linked to chronic myelogenous leukemia, BCR-ABL1 positive.