Immunocytological detection of isolated tumour cells in the bone marrow of malignant melanoma patients: a new method for the detection of minimal residual disease

Aims: Immunocytologically detected isolated tumour cells indicate a poor prognosis. This has been shown in breast, gastrointestinal and lung cancer, and might thereby help to indicate adjuvant therapy. Immunocytology has been proved to be a reliable technique and enables a phenotypic tumour cell characterization. We find this technique superior to molecular biological techniques such as reverse transcriptase polymerase chain reaction RT-PCR. So far, immunocytological studies have not been performed in malignant melanoma patients and our study aimed to establish this approach in melanoma patients. Methods: Twenty melanoma patients who underwent surgery for lymph-node metastasis using a radical lymphadenectomy were studied. Using the immunoperoxidase method, cytospins of bone marrow aspirates (1.5 x 10(6) cells per patient) were stained with the monoclonal antibody HMB-45. Nineteen patients who were surgically treated but did not suffer from malignant melanoma were included as a control group. Results: Four of the 20 patients showed isolated tumour cells in the aspirate. Three of these patients had stage IV disease. One patient had a stage III tumour (1/7; 14.3%). One patient was classified as stage II and did not show tumour cells in the bone marrow. No staining cells were found in the control group (n = 19). Conclusions: Our study demonstrates that the immunocytological approach can be used as a new technique to detect occult tumour cell dissemination in malignant melanoma patients and supports previous findings in carcinoma of the stomach, colon, pancreas and other tumours.