Case of Rapidly Expanding Conjunctival Malignant Melanoma Initially from Primary Acquired Melanosis Diagnosed 14 Years Earlier

Abstract

Primary acquired melanosis (PAM) of the conjunctiva is a potentially serious melanocytic lesion that can lead to the development of a melanoma. A 60-year-old woman noticed pigmentation of the conjunctiva of her left eye for more than 10 years. She underwent excisional biopsy combined with cryotherapy and was diagnosed with PAM without atypia by intraoperative consultation. She was followed for 7 years, and no changes were observed. Fourteen years after the initial biopsy, she noted a growing conjunctival tumor, and a melanoma was suspected. She underwent orbital exenteration and skin grafting procedures. Histopathological examination of the specimen led to a diagnosis of conjunctival malignant melanoma. Re-examination of the initial biopsy specimen revealed that there was a proliferation of melanocytes that partially expanded over the basal layer of the conjunctiva which had been diagnosed as PAM with moderate atypia. We conclude that this case of conjunctival PAM had progressed to a conjunctival malignant melanoma after 14 years. Pathological evaluation of intraepithelial lesions has its limitations; thus, cases of PAM, even in the absence of obvious atypia, require careful follow-up.

Keywords: conjunctival malignant melanoma; conjunctival melanoma; conjunctival tumor; malignant melanoma; primary acquired melanosis.

Figure 1

Initial slit-lamp examination of the left eye. Diffuse disseminated pigmentation in the conjunctiva can be seen around the cornea.

Figure 2

Rapid histopathological analysis of initial biopsy. There was no excess melanocyte proliferation in the epithelial layers. Thus, it was diagnosed as primary acquired melanosis (PAM) with reactive lymphoid hyperplasia and without atypia (A: low magnification, B; high magnification).

Figure 3

Seven years after excisional biopsy. No change was observed on the pigmentation in the conjunctiva.

Figure 4

Fourteen years after the excisional biopsy. Black tumor expanding from the fornix and disseminated pigments at bulbar and palpebral conjunctiva can be seen.

Figure 5

Histopathological specimen of the conjunctival tumor (H&E staining). Tumor was a conjunctival malignant melanoma.

Figure 6

Re-examined of the initial excised sample. (A) There is reactive lymphoid hyperplasia (original magnification, X 20). (B) Melanocytic nests partially expanded throughout epithelial layer of the conjunctiva scoring for conjunctival melanocytic intraepithelial neoplasia (C-MIN) of 2–3 (original magnification, X 200). The diagnosis was PAM with moderate atypia.