Transformation of cell type in uveal melanomas: a quantitative histologic analysis

To describe the cytologic transformation and tumor progression in a series of uveal melanomas.

Fifteen cases of uveal melanoma, treated by primary transscleral local resection without primary adjuvant treatment, needed enucleation because of local tumor recurrence. Cytologic and cell morphometric features of the primary tumor and the intraocular recurrence were compared, with evaluation of the amounts of intermediate cells, epithelioid cells, mitotic figures, and nucleolar area.

The cases were categorized into 2 groups, according to their cytologic characteristics. In the first group (5 cases), there was no cytopathological transformation in the recurrent tumor. The nucleolar area was increased in only 1 case. In the second group (10 cases), the recurrent tumors showed transformation into a more epithelioid cell type. In all but 1 case there was an increase in epithelioid cells in the tumor recurrence. The nucleolar area was increased significantly in all cases. The mean local recurrence interval in all cases was 15.3 months, with no difference between the groups. Death from metastases occurred in 7 cases in which the nucleolar area was 4.2 microm(2) in the primary tumor.

These findings demonstrate that, in an individual tumor, the cytologic phenotype can change considerably even after a relatively short time, resulting in an increase in tumor-related mortality.

Studies on the natural course of uveal melanoma have been very limited and based purely on observations on the progression of melanomas in terms of size and alteration of various clinical characteristics.