Immunoscintigraphy for ocular melanoma: a reliable diagnostic technique?

BACKGROUND

Immunoscintigraphy (IS) has recently been used as a diagnostic tool for ocular melanoma. We wanted to reevaluate published data in our own patients and to correlate immunoscintigraphic results with histologic findings and immunohistochemical characteristics of the tumour tissue.

METHODS

During a 4-year period, IS was performed on 35 patients (average age 64 years) with suspected ocular melanoma by i.v. injection of 225.28S, a monoclonal antibody against high-molecular-weight melanoma-associated antigen. Histology was available in 22 cases. Tumour tissue was evaluated for cell type, vascularization, necrosis, pigmentation, and lymphocytic infiltration, and immunohistochemistry was performed with 225.28S and antibodies against HMB-45, S-100 and vimentin. One hundred and two patients with metastasizing cutaneous melanoma served as controls. In these patients the identical immunoscintigraphic technique was applied.

RESULTS

IS yielded a positive result in about 50% of our patients with ocular melanoma, while in patients with cutaneous melanoma sensitivity was 89%. In five patients who turned out not to have melanoma, two false-positive results were obtained (one subretinal hemorrhage and one Wegener's granulomatosis). No correlation was found between any of the histological features or the immunoreactivity pattern and the immunoscintigraphic outcome. However, antigenic differences between ocular and cutaneous melanoma were evident.

CONCLUSION

We conclude that IS, using the antibody applied in this study, is of only limited value in patients with ocular melanoma. Our results suggest that antigenic differences, rather than histological characteristics or technical problems, are responsible for the low sensitivity in ocular melanoma compared to cutaneous melanoma.