Discussion:
The hamartomas present themselves in a heterogeneous way, being classified in three groups. Type 1 is relatively flat, without calcifications and translucent gray-white. Type 2 is elevated, multinodular, calcified, opaque and “blackberry” shaped. Finally, type 3 characterizes a transitional lesion between those already mentioned. Type 1 injury has been described as the most common form, occurring in up to 70% of cases. Type 2 represents 55% and type 3, 9% of patients6. Zhang et al showed the prevalence of type 1 RAH in 94% of cases, type 2 in 7% and type 3 in 19%7. These results coincided with the prevalence reported by Kiribuchi et al in Japan8, but very different from the prevalence in Western countries, which suggests the importance of ethnicity in RAHs development 7. These lesions can be found concomitantly. Zhang et al found more than one type of RAH in 17.4% of the TS patients7.
Pichi et al proposed a new classification of RAHs based on OCT findings: type I, flat lesion within the RNFL without retinal traction; type II, mildly elevated hyperreflective lesion (height <500 μm) with retinal traction and internal retinal disorganization; type III, elevated retinal mass (height >500 μm) mushroom shaped, with internal retinal calcification with “moth-eaten” appearance; type IV, elevated (height >500 μm) dome-shaped, non-calcified retinal mass with optically empty cavity9.
Mutolo et al proposed a new subcategory of hamartomas (Type IIb), in addition to type Iia lesions, described by Pichi et al as type II. Type Iib lesions were characterized by an elevated retinal mass (>500 μm) above the RNFL with or without retinal adhesion or traction on the tumor surface, associated with a heterogeneous intratumoral appearance, which could vary from a full appearance to the presence of tumors to the presence of intralesional little empty spaces or cysts, and to the existence of segmented vascular calcifications; inner retinal layer, outer retinal layer, and full retinal thickness can be involved with or without posterior optical shadowing4.
In our report, it was possible to observe 4 different spectra of lesions in the OCT. According to Pichi et al9, lesions can be classified into type I (lesion 4), type II – Iia in Mutolo et al4 classification – and type III (lesions 2 and 3, respectively). An injury does not fit this classification (lesion 1). Lesion 1 has type Iia features, but has a maximum thickness <500 μm. Another difficulty for classification was the involvement of the retinal layers. Even though lesion 2 was classified as Iia, it has a different involvement of the retinal layers when compared to lesion 1 – also classified as Iia. The difficulty found in this classification was also reported by Kato et al and Mutolo et al, which reinforces the need for more descriptive studies of OCT aspects4,10.
Zhang et al showed that more than half of type 1 RAHs are located in the temporal retina, often near the end of the arcades7. In our report, 66.6% of the lesions in the right eye and 100% of the lesions in the left eye were in the temporal region. However, calcified RAHs – especially type 2 – are more commonly found in the peripapillary region. The observation of greater retinal vascular diameters in the temporal retina, indicating a greater blood supply when compared to the nasal one, may explain the higher incidence of RAHs in this region7,11.
Demonstration of the microstructure of RAHs using OCT is not only useful for detecting small or semi-transparent lesions that are easy to miss on examination, but also facilitates the differentiation of RAH from retinoblastoma, combined retinal hamartoma, and choroidal tumors1,6. Furthermore, some authors have suggested that, over time, translucent tumors may evolve into multinodular lesions that have undergone cystic, hyaline or calcified changes, as if type 2 tumors represent a late stage of the lesions12, so, OCT may also facilitate the follow-up of lesions4,12.
Conclusion:
This study described 4 different spectra of hamartomas using OCT-SS, which allowed a deeper evaluation of the lesions. Hamartomas initially compromise the inner retina layers with progression to the outer layers as they grow and calcify. OCT is a non-invasive method which assists the diagnosis of subclinical lesions and clinical characterization of patients with TS. More descriptive studies of OCT aspects are needed to better classify retinal hamartomas, due to their high prevalence in patients with TS.