Pathology of the Head and Neck

Eye and Ocular Adnexa Chapter 10 291Fig. 10.12. Compound conjunctival naevus: the intraepithelialcomponent is represented by a band of clear melanocytes in thebasal layer of the epithelium. A small inclusion cyst is present, surroundedby unsuspicious naevoid cells with maturation to smallercells in the deeper part of the lesionFig. 10.14. Malignant melanoma arising from primary acquiredmelanosis with atypia: the conjunctival epithelium is ulceratedand the atypical cells spread into the underlying stromaspontaneously, can remain stationary or may progress tomalignant melanoma. Histologically, there is an increasein atypical melanocytes in the conjunctival epithelium(Fig. 10.13). The atypia can be graded mild to severe. Toexclude invasive growth, use of the immunohistochemicalmarker CD68 can be helpful in identifying melanin-containingcells in the stroma as macrophages.10.2.6.2.3 Malignant MelanomaFig. 10.13. Primary acquired melanosis with atypia: an almostcontinuous proliferation of atypical melanocytes is present in theconjunctival epithelium10.2.6.2.2 Primary Acquired MelanosisICD-O:8741/2Primary acquired melanosis (PAM) arises in middle-agedor elderly patients as a stippled, yellow-brown, flat pigmentationof the conjunctiva. Two subgroups of PAM can berecognised: PAM without atypia (benign acquired melanosis)and PAM with atypia. In benign acquired melanosis,there is hyperpigmentation of the basal layer, but there isonly a mild increase in melanocytes. The melanocytes canbe large, but show little or no cytologic atypia. Although theevolution of PAM is unpredictable, lesions without atypiahave a good prognosis. PAM with atypia can disappearICD-O:8720/3The majority of conjunctival melanomas arise withinprimary acquired melanosis with atypia. Developmentof a melanoma in a pre-existing naevus or de novo ispossible, but uncommon [44, 61]. In malignant melanomaclusters of atypical melanocytes are present in thestroma (Figs. 10.14, 10.15). The melanocytes are mostfrequently epithelioid, but can also be spindle-shapedor bizarre. The intraepithelial component shows large,atypical melanocytes, often without ascending cells.This differs from skin melanocytic lesions, where ascendingmelanocytes can be very helpful in diagnosinga malignant melanoma. These cytological characteristicsdo not seem to influence prognosis. Depth of thetumour, however, does have prognostic value: thicknessless than 1.5 mm means a low risk of metastatic disease.10.2.6.3 Other NeoplasmsLymphomas may involve the conjunctiva. Also, tumoursfrom adjacent locations may extend into this site. Theyare discussed under their appropriate headings.