Atypical retinocytoma with diffuse vitreous seeds: An insight.

Retinocytoma is a rare benign form of retinoblastoma. It is usually found on routine examinations and also while screening families of patients with retinoblastoma. Distinctive features are a translucent retinal mass with calcification, retinal pigment epithelial disturbance, chorioretinal atrophy and absence of growth. We report a case with all the above features along with diffuse vitreous seeds and optical coherence tomographic documentation of intralesional cavitary lesions.

Introduction

Retinocytoma was originally described by Gallie et al.[1] as a benign form of retinoblastoma which undergoes spontaneous growth arrest. Although intralesional cavitations[2] and localized vitreous seeds have been reported,[3] we report a patient with optical coherence tomographic (OCT) documentation of cavitary lesions and diffuse vitreous seeds, which have not been documented till date to the best of our knowledge.

Case Report

A 33-year-old male patient presented with divergent squint and diminution of vision in the right eye (OD) since early childhood. Best corrected visual acuity was 20/80 OD and 20/20 in left eye (OS). Family history was not significant. Except for exotropia OD, rest of the anterior segment examination was normal in both eyes. Fundus examination OD showed whitish elevated retinal lesion arising from the disc, with surrounding chorioretinal scarring [Figure 1] and diffuse vitreous seeds seen on wide field imaging [Figure 2]. It was 3 mm in height and 5.5 mm as the largest basal diameter. OS was normal. OCT showed two large cavitary lesions within the tumor with two calcified vitreous seeds [Figure 3]. B-scan ultrasound showed a mass lesion with multiple high-intensity spikes within the mass and in the vitreous, indicative of intralesional and vitreous seed calcifications [Figure 4]. No subretinal fluid was seen. Ultrasound did not show evidence of intralesional cavities. A-scan ultrasound showed high internal reflectivity in these regions, confirming the presence of calcifications. Past history revealed that the patient was examined at our satellite hospital 19 years back. Patient records showed unchanged clinical findings. Fundus fluorescein angiography done at that time showed superficial network of fine vessels in early phase with leakage in the mid phases and intense staining of mass in late phase. Computerized tomography scan showed mass lesion in right eye with calcification. A diagnosis of retinocytoma with vitreous seedings was made and the patient was advised four monthly follow-up. Since he had unilateral involvement and negative family history, the 8% risk of retinoblastoma in offspring was explained. Also, the patient was advised importance of regular follow-up for the rare, but possible risk of malignant transformation. However, he was lost to follow-up after 5 years.

Figure 1

Fundus photograph OD showing the translucent mass lesion with surrounding chorioretinal atrophy (black arrow)

Figure 2

Wide field imaging OD showing the mass lesion associated with diffuse vitreous seeds

Figure 3

OCT of the same eye showing a cavitation within the tumor (thick white arrow) with two calcified vitreous seeds on the left side (thin white arrows)

Figure 4

Ultrasound B-scan picture showing retinocytoma tumor with calcifications and vitreous seeds

Discussion

The incidence of retinocytoma in general population is not known. However, it is between 2% and 10% among the retinoblastoma population.[13] Retinocytoma has benign histopathological features, but can undergo malignant transformation into retinoblastoma in about 4% cases and thus requires periodic follow-up.[4] Majority of these patients are asymptomatic and the diagnosis is made only on routine eye examination or while screening families of patients with retinoblastoma. Distinctive features are translucent retinal mass (88%), calcification (63%), retinal pigment epithelial disturbance (54%), chorioretinal atrophy (54%) and absence of growth.[5] In our patient, apart from these typical findings, intralesional cavitation documented by OCT and diffuse vitreous seeds were noted. After 19 years, the lesion remained stable with no documented growth. Mere presence of vitreous seeds does not signify a malignant transformation, as other criteria have to be taken into account. Even though localized vitreous seeds have previously been described in three patients with retinocytoyma,[6] there have been no reports where seedings were as diffuse as in our patient. The diagnosis of malignant transformation, however, can be based on progressive opacification, and increase in size of the tumor and presence of irregular fine tumor vessels.[6] We have reported a case of retinocytoma with diffuse vitreous seeds and cavitary lesions on OCT; both these findings have not been described in the previous literature. It is important to recognize the atypical features of diffuse vitreous seeding and intralesional cavitary lesions of this benign retinal tumor, which does not require aggressive treatment, but regular periodic follow-up.

Despite the characteristic ophthalmoscopic features of retinocytoma as mentioned above, certain entities can closely resemble retinocytoma, like retinoblastoma and astrocytic hamartoma. Retinoblastoma is diagnosed prior to age 5 years and retinocytoma is usually diagnosed in adults. Although calcification is seen in both tumors, areas of chorioretinal atrophy and associated retinal pigment epithelial changes are uncommon in untreated retinoblastoma. In addition, dilated, tortuous retinal feeder vessels are a feature of retinoblastoma rather than retinocytoma. Characteristically, retinoblastoma will show growth within 4–6 weeks, whereas retinocytoma will appear unchanged. Astrocytic hamartoma is a benign retinal tumor and can also closely resemble retinocytoma because both lesions may be calcified. Calcification, when present, can demonstrate subtle differences, as it tends to be dull and chalky white in retinocytoma, whereas in astrocytoma it is more glistening yellow, resembling fish eggs. Surrounding retinal pigment epithelium alterations, a common finding in retinocytoma, is typically absent in astrocytic hamartomas as they are situated superficially in the retina.