Conjunctival malignant melanoma appears to spur lymphatic vessel proliferation

Br J Ophthalmol. 2009;93(11):1529-1534.

New lymphatic vessels were identified in and around tumors diagnosed as conjunctival melanoma, according to a study.

"Conjunctival [malignant melanomas] display tumor-associated [lymphatic vessels] within and around the tumor," the study authors said. "The [malignant melanoma] seems to induce lymphangiogenesis not only in the tumor, but also in its proximity."

Investigators analyzed clinical files and conjunctival specimens of 20 patients with histologically diagnosed conjunctival melanoma. They used LYVE-1 and podoplanin antibody staining to identify lymphatic endothelial cells and Ki67 to identify cell proliferation. Digital imaging was used to measure tumor area, area covered by lymphatic vessels, number of vessels, and vessel density inside the tumor and in the adjacent area.

Study results showed that in all specimens, lymphatic vessels were identified inside the tumor and in the adjacent area. Staining showed significantly more proliferating lymphatic endothelial cells inside the tumor and in a 300-µm area of surrounding tissue compared with normal conjunctival tissue.

Investigators found a slight correlation between tumor size and the number and area of lymphatic vessels within a 50-µm area surrounding the tumor, the authors said.

Results showed no significant associations between lymphatic vessels and histopathologic and clinical features such as location, shape, rate of relapse and rate of metastasis.

"Non-limbal tumors with involvement of tarsus or fornix showed a tendency towards a higher [lymphatic vessel density] compared with limbal tumors," the authors said.