Microsatellite analysis showing similar profile between metastases and peripheral blood lymphocytes (PBL)s of the patient. This assay is commonly used for linkage mapping studies, association studies, and identification of organisms. It has been reported to be useful for assessment of chimerism in graft-versus-host disease, for identification of the site of origin of unknown primary tumor, and for determination of donor-recipient origin in posttransplant lymphoproliferative disorders. Microsatellites are short runs of tandemly repeated DNA that represent a primary source of human genetic diversity. The variations in these repeats are used for genetic identification purposes. It is based on PCR amplification of various microsatellite loci (or markers) using fluorescently labeled forward and unlabeled reverse primers. The PCR amplicons are separated by size and the labeled products are identified using fluorescence detectors. In this case the DNA was extracted from pulmonary metastases, patients PBLs, and from healthy donor PBLs. Arrows indicate differences in the microsatellite markers used: 1 – Amelogenin locus in X/Y chromosomes (patient and metastases have XY profile (male), donor has XX profile (female)); 2 – locus vWA in chromosome 12p (heterozygous in patient's PBLs and metastases, homozygous in donor PBLs); 3 – D7S820 marker in chromosome 7q (homozygous in patient's BPLs and metastases, heterozygous in donor PBLs).