Expression of sex hormone receptors and cell cycle proteins in melanocytic lesions of the ocular conjunctiva

Background: Both dermal and ocular melanocytic nevi have been reported to undergo changes during pregnancy. This has been proposed to be related to hormonal influences; however, few studies have provided any proof. We therefore set out to evaluate the expression of sex hormone receptors and cell cycle proteins in melanocytic lesions of the ocular conjunctiva. Methods: Formalin-fixed, paraffin-embedded material from 76 tumors - 69 conjunctival nevi, 5 specimens of primary acquired melanosis (PAM), and 2 conjunctival melanomas - were included in a tissue microarray (TMA) format. The TMA sections were analyzed by immunohistochemistry with antibodies for progesterone and estrogen receptors, and cell cycle-related proteins (p16, MIB1-Ki67). Results: Progesterone receptors were highly (96%) and similarly expressed in all lesions. In addition, progesterone receptor expression showed a tendency to increase with age (p=0.06). In contrast, estrogen receptor expression was completely absent in all tumors. The cell cycle regulator p16 was expressed in 97% of the lesions. The proliferation marker MIB1-Ki67 was expressed at low levels (mean +/- SD: 13 +/- 14%) in 79% of the lesions. No differences of expression were found between the different lesions and nevi types. The mean age of the patients was highest in conjunctival melanoma (70 +/- 22 years), followed by PAM (60 +/- 19 years) and nevi (36 +/- 18 SD years). The different types of nevi also showed significant age dependency (junctional 25 +/- 17 years, compound 34 +/- 17 years, dermal 49 +/- 15 years). Conclusion: Our findings reveal the expression of progesterone, but not estrogen, in melanocytic lesions of the ocular conjunctiva. In benign conjunctival lesions, p16 and MIB1-Ki67 expression was comparable to that in benign nevi of the skin.