KEY FACTS
Terminology
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Testicular microlithiasis (TML): Presence of 5 or more microliths or microcalcifications in whole testis or 5 or more microliths per field of view
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Limited TML: Presence of < 5 microcalcifications per field of view
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Microcalcifications composed of hydroxyapatite, located within spermatic tubules
Imaging
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On US, seen as discrete, punctate, nonshadowing echogenic foci scattered within testicular parenchyma
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Majority are idiopathic; previous infection or trauma may also be responsible
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Clusters of microliths may represent testicular tumors even when no soft tissue mass can be identified
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Adjacent hypoechoic foci, if seen, could represent neoplasia
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May occasionally see comet-tail artifact
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High-resolution US (≥ 7.5 MHz) is modality of choice
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May occasionally see twinkling artifact on color Doppler
Top Differential Diagnoses
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Scrotal pearls (scrotoliths)
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Large-cell calcifying Sertoli cell tumor
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Testicular granuloma
Pathology
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Testicular neoplasia in 18-75%, intratubular germ cell neoplasia, germ cell version of carcinoma in situ
Clinical Issues
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Microlithiasis in absence of other risk factors is not indication for further sonographic screening or biopsy
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Follow-up US recommended in patients with risk factors, including personal/family history of GCT, maldescent or undescended testes, orchidopexy, testicular atrophy
Diagnostic Checklist
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If TML is seen, check bilateral testes carefully for any focal solid lesion
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Once germ cell tumor has been excluded, risk of cancer is very low unless risk factors present
Scanning Tips
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If TML is seen, check bilateral testes carefully for any focal solid lesion
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Scan carefully from medial to lateral in longitudinal plane and superior to inferior in transverse plane to detect limited TML
