Comparison of microcirculation patterns and MIB-1 immunoreactivity in irisand posterior uveal melanoma

Purposes: To compare melanomas confined to the iris and those involving eit her the ciliary body or choroid for the histologic features of microcircula tion patterns and tumor cell proliferation indices. Designs: Retrospective comparative human tissue study. Participants: Ninety-eight uveal melanomas were studied, including 18 tumor s confined to the iris, 30 tumors involving the ciliary body, and 50 tumors confined to the choroid. Methods: Formalin-fixed, paraffin-embedded sections from each tumor were st ained with hematoxylin-eosin and with periodic acid-Schiff. Adjacent histol ogic sections were stained with the MIB-1 antibody that reacts with the Ki- 67 antigen. Main Outcome Measures: Microcirculation patterns were assessed in the perio dic acid-Schiff-stained sections. Proliferative activity was assessed in th e MIB-1-stained sections. The mean MIB-1 positive cell count per high-power field (HPF) was calculated in 10 HPF (x 40) in the area of maximal immunor eactivity. Two observers evaluated each MIB-1-stained section, and the inte robserver reproducibility was assessed. Results: Histologic microcirculation patterns associated with death from me tastatic disease in ciliary body and choroidal melanomas (parallel vessels with cross-linking and networks of back-to-back loops) were not found in an y of the iris melanomas. By contrast, 34% and 63% of the choroidal and cili ary body melanomas, respectively, showed at least one of these patterns. Th e mean positive cell count per HPF +/- standard error was 19.9 +/- 3.5, 27 +/- 5.3, and 1.9 +/- 0.4 in choroidal, ciliary body, and iris melanoma, res pectively (P = 0.003, Kruskal-Wallis test). Conclusions: Melanoma confined to the iris is characterized by a low rate o f proliferation and the histologic absence of microcirculation patterns ass ociated with metastatic posterior uveal melanoma. Both features are consist ent with the relatively benign nature of iris lesions compared with melanom as involving the ciliary body or choroid. Ophthalmology 2001;108:367-371 (C ) 2001 by the American Academy of Ophthalmology.