Urogenital ImagingTesticular microlithiasis
(TM), a rare abnormality found in 0.5-0.6% of men. The sonographic appearance of TM is characteristic with multiple scattered intratesticular echogenic foci, usually without acoustic shadowing. Each echogenic focus represents an intratubular microlith composed of a
calcified core with surrounding layers of glycoprotein. These microliths are often distributed diffusely throughout the testicular
parenchyma, but they may be clumped or clustered. Typically, both testes are symmetrically involved, but asymmetry occurs in about 20% of cases. Unilateral involvement has also been reported. Although there is no standard definition of how many echogenic foci need to be visible in each testis to make the diagnosis of testicular microlithiasis, some authors have found it useful to subdivide this entity into two groups.
Cases in which five or more microliths can be demonstrated on a single ultrasound image are designated classical testicular microlithiasis (CTM). Cases which do not meet this arbitrary criterion are designated limited testicular microlithiasis (LTM). TM has been most commonly associated with cryptorchidism. Other associations have also been reported, including infertility and intraepithelial germ cell neoplasia. Attention is now being drawn to this association of TM with testicular malignancy, seen in about 40% of cases. The microliths may be seen within the tumour or along the periphery of the mass, as if the tumour displaced testicular parenchyma containing microliths. These observations raise the possibility that patients with TM are at increased risk for the subsequent development of testicular malignancy. The incidental diagnosis of TM is a relatively recent phenomenon, resulting from the wider application of sonography in evaluation of the scrotum. Since experience with TM remains limited, there are no studies documenting the importance of long-term follow-up of these patients. However, there are case reports of patients with TM who have developed testicular neoplasms. Until there is more definitive data regarding the risk of testicular neoplasia in TM patients, close clinical and sonographic follow-up is the most prudent course. In patients less than 50 years of age, testicular self-examination with yearly follow-up sonograms has been recommended. Any focal area of abnormality should be regarded with a high degree of suspicion of malignancy. Ultrasound is a very sensitive modality in the detection of testicular microlithiasis (Fig.1). On sonography there are tiny 1-2 mm in diameter disseminated echogenic foci (Fig.2). Microliths are tiny, and no acoustic shadowing is usually seen. Microlithiasis can be seen on MRI as well. On T1-weighted images, small scattered low-signal intensity foci can be detected. CT is extremely sensitive for the depiction of testicular microlithiasis, but is not clinically indicated.
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Longitudinal ultrasound image of the testis, demonstrating multiple tiny markedly echogenic foci, due to testicular microlithiasis.
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Testicular microlithiasis, Fig.1 | | Testicular microlithiasis, Fig.2 | |