A clinically challenging diagnosis of adenoma of the retinal pigment epithelium presenting with clinical features of choroidal hemangioma

Sohei Nakamura¹, Naofumi Hikita², Ryoji Yamakawa¹, Fukuko Moriya³, Hirohisa Yano³, Emiko Furusato⁴, J Douglas Cameron⁵, Elisabeth J Rushing<sup>4

1</sup>Department of Ophthalmology, Kurume University School of Medicine, Kurume, ²Fukubiru Hikita Eye Clinic, ³Department of Pathology, Kurume University School of Medicine, Kurume, Fukuoka, Japan; ⁴Department of Neuropathology and Ophthalmic Pathology, Armed Forces Institute of Pathology, Washington, DC, 5Departments of Ophthalmology and Laboratory Medicine and Pathology, University of Minnesota, Minneapolis, USA

Background: Adenoma of the retinal pigment epithelium (RPE) is a rare intraocular tumor that can simulate other pigmented tumors such as choroidal melanoma. We report a case of non-pigmented adenoma of the RPE initially diagnosed as choroidal hemangioma.
Case report: A 42-year-old woman presented to Kurume University Hospital in November 1992 with an orange-yellow tumor nasal to the optic disc in the left fundus. The tumor was 9.0 × 9.0 mm in diameter, 6.0 mm thick, and was characterized by high intensity on T1-weighted magnetic resonance imaging (MRI), low intensity on T2-weighted MRI, and enhancement on gadolinium MRI. Fluorescein angiography revealed early hypofluorescence and late hyperfluorescence of the tumor and retinal feeder vessels. By April 1996, exudate had developed around the tumor margins. The patient was treated with external beam radiation therapy (20 Gy) in July 1996, but the tumor did not diminish in size. Subsequently, she developed extensive loss of vision due to total retinal detachment. Accordingly, her left eye was enucleated in June 2005 because of severe ocular pain due to absolute glaucoma. Histopathological examination indicated that the tumor was contiguous with the normal surrounding RPE and was composed of cords and tubules of mostly non-pigmented spindle-shaped cells with round to oval nuclei and a small amount of cytoplasm containing melanin granules. The tumor cells were immunoreactive for vimentin, S-100 protein, and cytokeratin 18. The final diagnosis was adenoma of the RPE.
Conclusion: Adenoma of the retinal pigment epithelium may be associated with incompetent vessels leading to serous retinal detachment and extensive visual loss, and may exhibit clinical characteristics similar to choroidal hemangioma.

Keywords: adenoma, choroidal hemangioma, histopathology, retinal pigment epithelium