Surgical Resection of a Retinal Pigment Epithelial Hamartoma

Several darkly pigmented tumors affecting the macular area have beendescribed, including retinal pigment epithelial (RPE) hamartomas,¹ combined retina-RPE hamartomas, melanocytic nevi ofthe RPE (congenital hypertrophy of the RPE), choroidal nevus, and melanomasinvading the retina. Melanocytomas can rarely also be located in the maculararea without involving the overlying retina.

Retinal pigment epithelial hamartomas are focal, nodular, jet-blacklesions that usually appear to involve the full thickness of the retina andto spill onto the inner retinal surface in an umbrella fashion, frequentlyin the macular area.¹ Combined retina and RPEhamartomas can be papillary or nonpapillary, variably elevated pigmented lesionsat the level of the RPE with a thin semitransparent membrane partly coveringthe tumor surface.¹ There are various reportsin the literature of vitrectomy to peel the epiretinal component of theselesions,^2,3 with improvement ofvisual acuity. Melanocytoma is described as a darkly pigmented lesion of variablesize and shape located partly or completely in the optic nerve head. Sincethe clinical and histopathologic nature of the lesion was clarified, similartumors have been reported in other locations,^4,5 includingthe macula, where they always involve the choroid only.

We report an unusual pigmented macular tumor in a child that was surgicallyexcised. It was also studied histopathologically and diagnosed as an RPE hamartoma.

A 5-year-old white boy of Mediterranean descent was referred to us becauseof decreased visual acuity and a central scotoma in his left eye. The patientwas healthy and his medical history was unremarkable.

On examination, the patient’s best-corrected visual acuity was20/25 OD and 20/200 OS without esotropia. Results of examination were normalexcept those in the fundus of the left eye. Fundus examination of the lefteye showed a round, nodular-shaped, darkly pigmented mass involving the centralmacular area (Figure 1). The maximumdiameter and thickness measured by tridimensional ultrasonography were 1.2mm and 1.6 mm, respectively. The mass had a granular surface and very sharpmargins. Dilated tortuous retinal vessels appeared to be drawn inward towardthe base of the tumor. There was retinal thickening, an epiretinal membrane,and a green-brown reflex surrounding the tumor.

B-scan ultrasonography showed a smooth, solid, mushroom-shaped lesionwith a medium- to high-amplitude internal reflectivity. There was no evidenceof subretinal fluid or retinal detachment. Fluorescein angiography showeddilation and marked tortuosity of the retinal vessels surrounding the baseof the tumor and some late staining surrounding the tumor, suggesting thepresence of an epiretinal fibrous membrane (Figure2 and Figure 3). Computerizedperimetry confirmed the presence of a central scotoma corresponding to thearea of the tumor.

The extremely dark pigmentation was similar to that observed in melanocytomasand melanomas, but the unusual location, the absence of fibrillated margins,the epiretinal membrane, and the green-brown reflex in the subretinal areasuggested otherwise. Because the diagnosis was not reached with clinical examinationand noninvasive tests, we decided to perform a vitrectomy to obtain a samplefor diagnostic biopsy, relieve the retinal traction around the tumor, and,if possible, resect the tumor completely.

A 3-port pars plana vitrectomy was performed, and the posterior hyaloidmembrane was dissected. With a bent microblade, a dissection plane was createdto release the traction over the retina surrounding the tumor. Between theinner retina and the outer part of the tumor, a dissection plane was found,and by means of a bimanual technique, the entire tumor was resected and removedcompletely from the retina, leaving a craterlike configuration in the maculararea (Figure 4).

The postoperative period was uneventful. The craterlike appearance ofthe macular area resolved by 1 month postoperatively, and 1 month after surgeryvisual acuity had not changed from the previous 20/200. Treatment of the amblyopiawith occlusion of the right eye achieved a final visual acuity of 20/80. Thecentral scotoma resolved.

By light microscopy, the tumor was composed of tightly packed, maximallypigmented, round cells (Figure 5). Onbleached preparations (Figure 6), thecells were large and plump, round, or polyhedral with abundant eosinophiliccytoplasm and uniform, ovoid or round, benign-appearing nuclei. The cellsexpressed S100 protein (Figure 7), andepithelial markers were found to be positive (Figure 8) with the use of cytokeratin markers. Mitotic figures andother evidence of anaplasia were not observed. No newly formed blood vesselswere found within the tumor.⁶

This case proved to be an unusual diagnostic problem from both clinicaland anatomic standpoints. There are 2 melanin-bearing cells of the eye thatmay cause pigmented tumors: uveal melanocytes and RPE cells. Uveal melanocytesmay produce disorders such as melanocytoma, nevus, and melanoma. Melanocytomasare considered to be derived from a massive accumulation of ectopic uvealmelanocytes during embryogenesis and classically affect a portion of the opticnerve. A melanocytoma that is located in the retina without involving theoptic disc is exceptional. Recently, Jürgens et al⁵ observeda presumed retinal melanocytoma involving the macular area, but it was notconfirmed histopathologically.

The RPE cells may produce congenital hypertrophy, hamartomas, adenomas,and adenocarcinomas. Retinal pigment epithelial hamartomas, also referredto as “congenital pigment epithelial adenomas” or “primarypigment epithelial hyperplasia,” are focal, nodular, jet-black lesionsthat usually appear to involve the full thickness of the retina and oftenextend onto the anterior surface of the retina in a mushroom configuration.¹ Recently, a study of 5 cases of hamartoma of the RPEwas published by Shields et al,⁷ in which theauthors described 5 cases similar to ours, but all of them adjacent to thefovea and with good visual acuity.

Clinically the tumor could be classified as an RPE hamartoma becausethe age of the patient, the jet-black lesion involving the retina, and themushroom shape in the macular region favored this diagnosis. The appearanceof the tumor and its location were similar to an RPE hamartoma reported byGass.¹ However, the prominent shape and themargins, the mushroom appearance on B-scan ultrasonography, and the green-brownreflex in the subretinal area suggested a uveal melanoma with retinal involvement.

We observed intraoperatively that the tumor was located over the retina,and after its dissection and removal, the full-thickness retina, with thexanthophyll pigment, and the fovea were found behind the tumor. Therefore,the classic assumption that the RPE hamartoma originated in the RPE, withposterior involvement of the full-thickness retina extending through the internallimiting membrane onto the inner retinal surface, was not confirmed in ourcase, although Gass¹ also described hamartomaswith a superficial location. In the present case, tumor excision permitteda complete histopathologic examination and made it possible to establish thediagnosis of RPE hamartoma, rule out the possibility of malignancy, and improvethe visual acuity after amblyopia therapy was performed.

Correspondence: Dr García-Arumí,Instituto de Microcirugía Ocular, C/Munner, 10, 08022 Barcelona, Spain(17215jga@comb.es).

Financial Disclosure: None.