Macrophages and microcirculation in regressed and partially regressed irradiated choroidal and ciliary body melanomas

To investigate how tumour-infiltrating macrophages and microcirculation attributes of uveal melanomas regressed after brachytherapy and whether primarily enucleated melanomas differ.

A case-control analysis of 34 matched pairs of irradiated and nonirradiated choroidal and ciliary body melanomas with main outcome variables being area of necrosis, extravascular matrix loops and networks, tumour-infiltrating macrophages in nonnecrotic areas identified with mAb PG-M1 to the CD68 epitope, and microvascular density (MVD) determined by mAb QBEND/10 to the CD34 epitope.

Comparison of primarily enucleated eyes to eyes with irradiated, secondarily enucleated melanomas revealed significantly more necrosis (median difference, +9%, P = 0.0012) and lower MVD (median difference, -10 counts/0.313 mm(2), P = 0.011) in the latter. In eyes managed with brachytherapy, loops and networks tended to be less frequent (P = 0.077). Number and type of macrophages were similarly distributed, being moderate to high in about 95% (P = 0.67) of the matched pairs, and intermediate to dendritic in 79% (P = 0.90). In the irradiated eyes, presence of epithelioid cells and the number and type of macrophages showed no association with microcirculation attributes, whereas in the primarily enucleated tumours, high number of macrophages was associated with high MVD (P < 0.001).

This study suggests that regression after brachytherapy reduces MVD. The difference cannot be attributed to different numbers of tumour-infiltrating macrophages and different cell type in nonnecrotic areas of the tumour.