IMAGING

Testicular microlithiasis: prospective analysis of prevalence and associated tumor
Middleton WD, Teefey SA, Santillan CS
Mallinckrodt Institute of Radiology, Washington University School of Medicine,
St Louis, MO, USA
Radiology 2002; 224:425-8

• Purpose: To evaluate testicular microlithiasis (TM) prospectively with modern state-of-the-art equipment.
• Material and Methods: Information concerning indication for examination, presence and degree of TM, presence of testicular tumor, and patient age was prospectively recorded for all patients referred for scrotal ultrasonography between 1996 and 1999. High-frequency linear transducers (7.5 MHz or higher) were used. TM was divided into classic (CTM) and limited (LTM) on the basis of the presence of five or more microliths on one or more images of the testes. Fisher exact tests were used for determining significant differences in proportions.
• Results: Data in 1,079 patients were analyzed. The overall prevalence of TM was 18.1% (195 of 1,079). Forty (3.7%) patients had CTM, and 155 (14.4%) had LTM; 15 (1.4%) had tumors visible at US. Tumors were present in three (8%) of 40 patients with CTM (seminoma in two, embryonal cell in one), nine (5.8%) of 155 with LTM (seminoma in six, mixed germ cell in one, Leydig cell in two), and three (0.3%) of 884 with no TM (seminoma in two, other in one). There was no difference between CTM and LTM (P = 72) in the rate of coexisting tumor. There was a significant difference between no TM and CTM or LTM (P<=.001) in the rate of coexisting tumor. Eighty percent (12 of 15) of patients with tumor at presentation had CTM or LTM.
• Conclusion: Approximately one of 27 patients had CTM, and one of seven had LTM. Although a majority of patients with testicular tumors had coexistent TM, more than 90% with TM (both CTM and LTM) did not have tumor at presentation.
  
  
• Editorial Comment
  Testicular microliths (TM) occur in the lumen of seminiferous tubules, and represent calcified cores smaller than 1mm in diameter, surrounded by collagen fibers. TM is usually furthered categorized as classic microlithiasis (CTM), if at least one image of the scrotal US examination shows five or more microliths in either or both testes, and LTM, when the image show at least one microlith. TM has been considered in the last few years an imaging marker of testicular cancer, with several reports recommending serial scrotal ultrasound in order to detect testicular tumor in asymptomatic patients (1,2). Some authors reported that 30-40% of patients with TM had testicular tumors. However, others studies has shown that testicular microlithiasis is common in a screening in an asymptomatic population, with a prevalence of 5.6%, and a significant higher prevalence among afro-Americans, and that this entity is not likely associated with testicular cancer (3).
  The authors presented a prospective study of one thousand seventy-nine patients which underwent scrotal US. TM was detected in 18.1% of patients; 3.7% had CTM, and 14.4% had LTM. The prevalence of testicular tumor was 1.4% (15 of 1,079), with 80%(12 of 15) associated with CTM or LTM at presentation. Only 8% (3 of 40) patients with CTM had tumors, and 5.8% (9 of 155) with LTM had tumors. On the other hand, only 0.3% (3 of 884) patients without TM had testicular tumor. This results shows that there is a significant difference in patients with and those without TM, and this fact emphasizes that TM and tumors are linked in some way. The authors concluded that the retrospective studies performed in the past have led to underestimation of the prevalence of TM, and overestimation of the risk of coexisting tumor. They estimated that CTM would be detected in one of every 27 patients, and LTM in one of every 7 patients. They also estimated that the risk of coexisting TM and testicular tumors is 5-10%, rather than 30-40% as previously reported.
  As we can see, this subject has becoming less and less controversial, but a large long-term prospective study using high-resolution US for follow-up is needed. From a practical point of view, such study is necessary to demonstrate whether the patients with TM need or not serial US examination, or if they can be safely managed only by clinical follow-up.

References
1. Winter TC 3rd, Zunkel DE, Mack LA: Testicular carcinoma in a patient with previously demonstrated testicular microlithiasis. J Urol. 1996; 155:648.
2. Golash A; Parker J, Ennis O, Jenkis BJ: The interval development of testicular carcinoma in a patient with previous demonstrated testicular microlithiasis. J Urol. 2000; 162:239.
3. Peterson AC, Bauman JM, Light DE, McMann LP, Costabile RA: The prevalence of testicular microlithiasis in an asymptomatic population of men 18 to 25 years old. J Urol. 2001; 166:2061-4.

Dr. Adilson Prando
Department of Radiology
Vera Cruz Hospital
Campinas, São Paulo, Brazil