Case Presentation - Fall, 2008

ThinPrep® non-gyn cytology, Cellient® cell block

NOTE: The diagnosis and analysis for this case study were provided by an independent physician. All conclusions and opinions are those of the physician and not Hologic, Inc.

History: 65 year old male

Specimen type: Right eye choroidal lesion fluid

The donating laboratory would like to remain anonymous.

Melanocytoma, also known as Magnocellular Nevus, is a rare benign nevus found in the optic disc region of the eye but can also occur in the choroid, iris or ciliary body. This congenital, nonhereditary lesion usually occurs unilaterally, with a slight prevalence in females (58%) and is most likely present at birth. Diagnosis occurs upon routine ophthalmologic exam with the lesion presenting as a deeply pigmented mass consisting of pigmented melanocytes with sharply circumscribed borders. The age of diagnosis ranges from 14 years of age to 80 years of age. Melanocytomas have a slow growth rate and are usually asymptomatic unless enlargement occurs. With growth and possible necrosis, the lesion can compress on the optic nerve causing partial or total vision loss. Transformation into malignant melanoma is possible. However, very rare cases of this transformation have been documented.

Currently, there are no treatments to prevent or stop the growth of melanocytoma. Because of this, patients must be closely observed and provided with careful follow up, including serial fundus photography to document growth. Sensitive counseling addressing the possibility of vision loss should also be provided. In rare events of tumor growth, surgical removal of the eye is necessary.

Cytology of melanocytoma yields a densely pigmented specimen that may require bleaching to appreciate cellular detail. Upon bleaching, the cells present are oval to round in shape with abundant cytoplasm, small nuclei and few nucleoli. Neither chromatin migration nor mitotic figures are seen. Two cell types are present. Type I cells are large, round, deeply pigmented with large melanosomes. Type II cells, which grow slowly, are smaller, spindle-shaped cells, less pigmented and have small melanosomes.

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