Abstract
Purpose
To describe the clinical and histopathological features of a case of choroidal melanocytoma treated by local resection.
Observations
A 73-year-old man was referred to our hospital with a clinical diagnosis of choroidal melanoma. His best corrected visual acuity at presentation was 20/20 OU. Ocular fundus examination of his right eye showed a pigmented intraocular tumor. Local resection of the tumor was performed under general anesthesia. Histopathological examination of the excised tumor showed proliferation of round to ovoid cells with abundant cytoplasm containing many melanosomes and uniform nuclei and these histopathological findings were compatible with a diagnosis of choroidal melanocytoma. Visual acuity of 20/200 OD has been maintained for over 4 years without local recurrence.
Conclusions and Importance
Clinical diagnosis of choroidal melanocytoma, especially differentiation from melanoma, is difficult and challenging. Local resection of the tumor allowed study of the histopathological features of the choroidal melanocytoma and maintained tolerable vision in the current case.
1
Introduction
Melanocytoma, a variant of the melanocytic nevus, is found equally in all races, unlike uveal melanoma which is uncommon in African American and Asian. Histopathological examination of melanocytomas, especially choroidal melanocytoma, is rarely reported, because of their benign and less sight-threatening nature.
We report the clinical and histopathological features of a case of choroidal melanocytoma successfully treated by local resection.
2
Case report
A 73-year-old Japanese man was referred to the Department of Ophthalmology, Tokyo Medical University Hospital in March 2015 with a clinical diagnosis of choroidal melanoma in the right eye. He was aware of floaters in his right eye since 5 months before presentation. His best corrected visual acuity (BCVA) at presentation was 20/20 OU, and intraocular pressure was 14 mmHg (OD) and 15 mmHg (OS). Slit lamp examination revealed mild cataract in both eyes. Ocular fundus examination of his right eye showed a brownish tumor protruding from the superior mid periphery and diffuse pigmented opacification in the vitreous ( Fig. 1 A and B). Ultrasonography demonstrated a solid mass consistent with an intraocular lesion. Single photon emission computed tomography (SPECT) using N-isopropyl-p-[ 123 I] iodoamphetamine ( 123 I-IMP), which is useful for the diagnosis of uveal melanoma, , was negative. Differential diagnosis included pigmented intraocular tumors such as choroidal melanoma, and adenoma or adenocarcinoma of the retinal pigment epithelium. Two months later, local resection of the tumor (eye wall resection) was performed with the patient’s informed consent.
Surgery was performed under general anesthesia with low systolic pressure to control intraoperative bleeding. After phacoemulsification of the lens, the bulbar conjunctiva was dissected along with limbus, and the superior rectus muscle was temporarily detached to obtain a wide surgical field. After the margin of the intraocular tumor was delineated using a 23-gauge endoscopic system, a half-thickness scleral flap with a posterior hinge was made, and cryopexy and diathermy were applied around the scleral bed. Subsequently, the edge of the scleral bed was incised with a slit knife while keeping a safety margin of approximately 1 mm, and then the intraocular pigmented tumor with retina was completely removed. The scleral flap was sutured back with 9–0 nylon and the superior rectus muscle was replaced. Vitrectomy was performed to remove vitreous and intraocular hemorrhage, and sulfur hexafluoride (SF 6 ) gas was injected as tamponade. Finally, the bulbar conjunctiva was sutured.
A gross specimen was excised with the scleral base measuring 11 mm × 10 mm ( Fig. 2 A). Histopathology showed heavily pigmented tumor with focal necrosis between the atrophic retina and sclera ( Fig. 2 B). The tumor was composed of round to ovoid large cells containing many melanosomes in the cytoplasm ( Fig. 2 C). Bleached preparation revealed uniform nuclei with low nuclear-to-cytoplasmic ratio ( Fig. 2 D). Immunohistochemical staining showed that the tumor cells were partially positive for HMB45, diffusely positive for Melan A and negative for S100 ( Fig. 3 A, B, C). Ki-67-positive cells were less than 5% ( Fig. 3 D). These histopathological findings were compatible with a diagnosis of choroidal melanocytoma.
