Uveal metastases are the most common intraocular malignancies, and up to 10% of patients with metastatic cancer have intraocular involvement (21, 22). One percent of all uveal metastases originated from TCs, in which the PTC is the most common type (5, 9, 23). In our study, 34% of patients with uveal metastases had PTC, and 32% had FTC. MTC accounts for 5–8% of all TCs (24), while in our study, 21% of patients with uveal metastases had MTC, which means the ratio of MTC in uveal metastases was higher than expected.
As life expectancy rises and treatment options improve, the number of patients with intraocular involvement will increase (13). In this study, patients were reported from 20 different countries. Most were reported from European countries and the United States, high-income countries with high facilities and life expectancies.
In this study, 56% of patients with uveal metastases as the primary site of the thyroid were males, and the difference between the two genders was trivial. Welch et al. (25) studied 1,111 patients with UM from all primary sites and reported that 36% of patients were males. Furthermore, In a study by d’Abbadie et al. (12), 123 patients with CM were examined, and 20% of patients with CM with any primary sites were males. This difference between our study and d’Abbadie’s and Welch’s can be due to the different populations of these studies because the most common primary site for CM is the breast, which is more common in females.
d’Abbadie et al. (12) reported that 75% of patients have unilateral choroidal metastases, which is three times more common than bilateral metastases; also, we found that 75% (35 patients) had unilateral uveal metastases. In our study, there was no remarkable difference in right or left eye involvement, the reason for which may be the similar hematogenous route from the thyroid to the eyes. Uveal metastases arising from the gastrointestinal tract are more commonly reported in the left eye. This laterality may be due to the more direct pathway from the aorta to the left carotid artery (26).
In uveal metastases cases, the ophthalmic symptoms, such as decreased VA, may be prior to other symptoms. In our study, 15% of patients had ophthalmic symptoms prior to the diagnosis of TC. As similar, Welch et al. (25) reported that 7% of patients diagnosed with TCs had ophthalmic symptoms prior to diagnosis.
In this study, the mean interval of uveal metastases detection after proven TCs, was seven years; however, the range was too broad and the population too small to generalize the mean. Besic et al. (27), in 2013, in a study on 22 patients with CM of thyroidal origin, reported that the mean interval from diagnosis of TC was 10.4 years. Furthermore, Welch et al. (25) reported that the mean interval of UM from thyroidal origin was 13 years, which is relatively longer.
In our study, 84% of patients had choroidal involvement, the most commonly involved part, followed by the iris and ciliary body. Our findings are similar to previous studies (11, 28–30). The bigger share of CM from UM might be due to the rich blood supply to the choroid via the posterior ciliary arteries. This facilitates a greater volume of blood flow and is associated with a greater risk of metastatic emboli compared to the anterior ciliary vessels that supply blood to the iris. In addition, the upper temporal and posterior pole were the most common locations for CM. Furthermore, Freedman et al., in a review of 141 eyes, reported that 40% of CM are located in the macular region, which may be due to the different blood flow of the macular area (31).
CM has been reported to appear as a white or yellow dome-shaped mass associated with subretinal fluid with orange variations in the cases of TCs(32). In our study, in the few cases that reported the ophthalmoscopy findings, the most commonly reported appearance was white, yellow, and orange lesions.
In a study by shields et al. (13), among 479 eyes with choroidal metastases, 92% of the CM with any primary sites were located posterior to the equator. On the other hand, Besic et al. (27) reported that patients with CM typically presented with blurred vision and decreased VA in 70–81%. Similarly, we found that the first symptom of uveal involvement in 82% of patients decreased VA or blurred vision. Therefore, this may be due to the high involvement of the postquatorial region and the frequent development of subretinal fluid in CM. Furthermore, 9 of 13 patients with iris or ciliary body metastases had decreased visual acuity, mainly due to seeding to the anterior chamber or the development of secondary cataracts, as these lesions cause inflammatory symptoms more frequently than choroidal lesions (33, 34).
Management of patients with uveal metastases, especially CM, depends on the systemic status and the number and location of the lesions. Treatment options include systemic chemotherapy, immunotherapy, hormone therapy, external beam radiation therapy (EBRT), photodynamic therapy (PDT), brachytherapy with 125I episcleral insertion, and enucleation. The treatment of choice remains EBRT. As with other forms of radiation, it induces DNA damage to the rapidly growing tumor cells (35, 36). Observation may be considered for small peripheral metastatic lesions in patients with poor systemic status. Enucleation is usually considered for blind painful eyes, loss of vision, and persistent symptoms (32, 37). Despite all these treatment options, there are limited data regarding treatment efficacy.