Expression of cell adhesion molecules and tumour infiltrating leucocytes in conjunctival melanoma

Very little is known about the immunology of conjunctival melanoma. We investigated the expression of cell adhesion molecules and the grade of tumour infiltration with lymphocytes and macrophages as important members for the communication between tumour cells and the immune system.

Archival material from 35 conjunctival melanomas was used for immunohistochemical detection of intercellular cell adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1), neural cell adhesion molecule (NCAM), CD3 and CD68 using monoclonal antibodies. Histological and clinical data for these tumours were assessed.

ICAM-1 was expressed in 34 of 35 tumours; in 20 cases, more than 50% of the cells stained ICAM-1 positive. VCAM-1 was expressed in 21 of 34 tumours; in 17 cases, only a small proportion (1-25%) stained VCAM-1 positive. NCAM was expressed in 14 of 34 tumours; in 11 cases, only a small proportion (1-25%) stained NCAM positive. CD3-positive leucocytes were found in 26 of 32 tumours, whereas CD68-positive leucocytes were present in 33 of 34 tumours. Cox regression analysis revealed that patients with NCAM-positive tumours had a 6.4-fold higher risk of dying from conjunctival melanoma (P = 0.02). NCAM-positive tumours were preferentially (P = 0.03) located in prognostically 'unfavourable' areas (i.e. fornices, palpebral, caruncle) and had no or only a weak CD3-positive infiltrate (P = 0.03).

ICAM-1, VCAM-1 and NCAM are differentially expressed in conjunctival melanoma. Leucocytes were present in almost every tumour. The association between NCAM expression and prognosis may be related to the differential anatomical tumour location of NCAM-positive and NCAM-negative tumours, and should be considered a preliminary observation due to the limited statistical power of this study.