Donor origin of neuroendocrine carcinoma in 2 transplant patients determined by molecular cytogenetics.

Organ transplant recipients have an increased tumor incidence owing to their immunocompromised state. The origin of such tumors, whether donor or recipient, will have a clinical impact on decision-making concerning immunosuppressive therapy, retransplantation, and for recipients of other organs from the same donors. We report molecular cytogenetic determination of donor origin in 2 cases of small-cell neuroendocrine carcinoma developing in sex-mismatched transplant recipients (kidney and liver). Fluorescence in situ hybridization (FISH) analysis was performed on liver core needle biopsy material from the liver transplant patient and on liver fine needle aspiration cytopreparations from the kidney transplant patient. The results for the liver transplant patient were confirmed with microsatellite allelic analysis and with comparative genomic hybridization. In both cases, FISH showed the presence of only X chromosomes within the tumor cells, indicating the donor origin of the neoplasms. FISH is an excellent method to determine neoplastic origin in sex-mismatched transplant patients. HUM PATHOL 31:1425-1429.