Differentiation between cutaneous form of adult T cell leukemia/lymphoma and cutaneous T cell lymphoma by in situ hybridization using a human T cell leukemia virus-1 DNA probe

Adult T cell leukemia/lymphoma (ATLL) shares overlapping clinicopathological features with cutaneous T cell lymphoma (CTCL), requiring detection of monoclonal integration of proviral DNA of type 1 human T cell leukemia virus for its differential diagnosis from the latter. We applied in situ hybridization (ISH) and polymerase chain reaction (PCR) to paraffin sections from 63 Japanese autopsy cases that had been diagnosed as CTCL in earlier years when ATLL was still not widely known. Eleven and two cases with confirmed diagnoses of ATLL and CTCL served as positive and negative controls, respectively. It was found that ISH was positive in 7 of 63 test cases and 10 of 11 positive controls, whereas PCR was positive in none of the test cases and eight of the positive control cases. Two negative controls were negative for both ISH and PCR. We conclude that ISH is superior to PCR for detecting type 1 human T cell leukemia virus proviral DNA on paraffin sections and that the ISH method is useful for differentiating CTCL from the cutaneous form of ATLL.