Ultrasonography in necrotic choroidal melanoma.

Uveal melanoma (UM) is the most common primary intraocular malignancy in adults, originating in the uveal tract of the ocular globe. Spontaneous necrosis of choroidal melanomas is very rare, but some UMs may be predisposed to spontaneous necrosis due to rapid growth. The diagnosis of an extensively necrotic uveal melanoma can be challenging, because the associated intraocular hemorrhage makes impossible the direct tumor visualization during ophthalmoscopy. Ultrasonography is an imagistic tool based on sending and receiving sound waves (frequency above 20,000 Hz) with a probe which contains a piezoelectric transducer and works like a transmitter and receiver of sound waves in the same time. Ocular ultrasonography is the most commonly used imaging technique for determining the presence of a uveal melanoma, especially in opaque ocular media when dilated fundus examination of the eye cannot be made. In ophthalmology, we use two types of sound waves: an A-mode scan which uses frequencies of 8 MHz, and a B-mode scan for the visualization of intraocular structures which uses frequencies of 10 MHz. Ocular ultrasonography has many advantages in clinical practice, due to availability, no exposure to radiation and to low price. This article presents the difficulties associated with the diagnosis of necrotic uveal melanoma in the absence of fundus eye examination due to ocular opaque media. In this case, we should do the differential diagnosis with other pathologies that could resemble echographically uveal melanoma. In cases when ultrasonography cannot establish a clear diagnosis, we should use ancillary test. [ABSTRACT FROM AUTHOR]