the ultrasound ( us ) appearance of testicular microlithiasis ( tm ) was first described by doherty et al .   in 1987 .
the prevalence of tm in symptomatic korean men was found to be 6.0% with significant co - occurrence of tm , testicular cancer , and infertility by yee et al .  
although the cause - and - effect relationships are unclear , tm has been seen in patients with cryptorchidism , varicoceles , infertility , testicular torsion , klinefelter syndrome , pulmonary alveolar microlithiasis , neurofibromatosis , acquired immunodeficiency syndrome , intratubular germ cell neoplasia , and most importantly , primary testicular neoplasms .
reported that 74% of testes with tumors had associated ipsilateral tm on radiological inspection ; whereas , only 8% of testicular specimens with benign conditions had microcalcifications .
although chen et al .   reported that there was a significant difference in the rate of malignancy in males with tm compared with those without tm , the question remains whether tm independently increases the risk of testicular malignancy in taiwanese men .
, after reporting an association between tm and testicular tumor specimens , suggested in 1982 that radiographic studies be incorporated into diagnosing tm because of the perceived risk for testicular cancer in testicles with microlithiasis
performed us follow - up in 9 of 22 patients with tm for a mean of 32 months without any newly developing tumors being diagnosed .
reported similar results ; therefore , a regular scrotal us is controversial in asymptomatic tm patients .
the current recommendations , including those of the european association of urology , are that the presence of microlithiasis alone is not an indication for a regular scrotal us in the absence of other risk factors ( size<12 ml or atrophy , inhomogeneous parenchyma ) .
however , there have been no reports describing the changes in calcification over time in pediatric patients with tm .
the study protocol was approved by the institutional review board of the asan medical center .
the medical records from july 1997 to august 2014 of the asan medical center , a tertiary referral center , were retrospectively screened for patients diagnosed with tm by scrotal us .
twenty - three tm patients were included who had undergone scrotal us at least twice .
we analyzed the patient characteristics , clinical manifestations , specific pathological features , and clinical outcomes .
we measured the calcified area in maximum cross - sectional area , and we compared the calcific density in the initial diagnostic us and the final follow - up us .
we defined the testis and the calcified area in terms of their maximal cross - sectional area and calculated those areas using image j software ( national institutes of health , bethesda , md , usa ) ( fig .
patients that showed microlithiasis in three or more sections were defined as diffuse type , and patients with microlithiasis in less than three sections were defined as focal type ( fig .
we classified the patients into three groups according to the change of microlithiasis : an increased group , 20% increase in microlithiasis ; a decreased group , 20% decrease in microlithiasis ; and a no change group , < 20% increase or decrease .
differences were analyzed by a paired t - test , and crosstabs were used to assess dependent samples . in this study p - values < 0.05 were considered statistically significant .
the mean age at presentation was 11.34.6 years , and the follow - up period ( interval of fist us and last us ) was 79.138.8 months ( range , 25.4 - 152.9 months ) .
the mean age at last follow - up was 17.85.8 years ( range , 6.4 - 26.9 months ) .
follow - up occurred for 19 of 23 patients over puberty ( defined as > 13 years old ) .
of the 23 patients 20 had bilateral tm , 2 patients had unilateral tm , and 1 patient had an atrophic testis .
less frequent comorbid conditions included testicular torsion ( 3 patients , 13.0% ) , epididymitis ( 3 patients , 13.0% ) , varicocele ( 2 patients , 8.7% ) , hydrocele ( 2 patients , 8.7% ) , and epididymal cyst ( 2 patients , 8.7% ) .
calcific density was increased at the last follow - up us compared with the initial us ; however , this finding was not statistically different ( 3.74%6.0% vs. 3.06%4.38% , respectively , p=0.147 ) .
we divided the subjects into two groups ( focal vs. diffuse ) based on the distribution of tm .
we classified 23 testes as having focal tm and 20 testes as having diffuse tm .
in focal tm calcific density decreased but not significantly ( 0.72%0.55% vs. 0.66%1.03% , p=0.813 ) . on the other hand ,
the calcific density of diffuse tm show a trend toward increase ( 5.8%5.2% vs. 7.3%7.4% , p=0.457 ) ( table 2 ) ( fig .
3 ) . to clarify the tendency of tm calcification toward increase vs. decrease we divided the subjects into three groups based on the calcific density change of tm ( increase : increased > 20% ; decrease : decreased > 20% ; no change : < 20% increase or decrease ) .
we categorized 14 testes as increased , 18 testes as decreased , and 11 testes as no change .
half of the patients with diffuse tm were assigned to the increased group , a proportion significantly higher than focal tm ( 10/20 [ 50% ] in diffuse tm , 4/23 [ 17.4% ] in focal tm , p=0.049 ) ( table 3 ) .
in addition , 5 of 8 testes with cryptorchidism ( including 2 with bilateral cryptorchidism ) were categorized into the increased group .
previous tm studies have focused only on the relationship between tm and testicular cancer , and not on the natural course of this disease progression . in our current study , we report the natural course of calcific density changes in pediatric tm during pubertal development .
the mean age at presentation was 11.3 years and the mean follow - up period of approximately 5 years allowed follow - up of 23 patients over pubertal development . despite a follow - up interval that allowed potential pubertal changes to the testis , none of our patients developed testicular cancer or new abnormal symptoms . by contrast , there are some reported cases of patients with a known tm on us exam that eventually developed a primary testicular cancer .
reported a yolk sac tumor developing in a 17-year - old boy being followed for bilateral tm that was originally detected because of an initial sonographic evaluation of unequal sized testes .
reported the case of a man with tm seen on a sonograph performed due to bilateral testicular pain who presented three years later with a metastatic germ cell tumor of the left testicle .
although , an association between tm and subsequent testicular tumors appears likely , whether there is a true cause - and - effect relationship remains unknown .
( 7 patients , 45 months)-used us to follow patients with tm and , similarly to our present results , did not detect the appearance of new testicular tumors .
compared with these prior studies , our current study incorporates more patients and a longer - term follow - up extending through puberty .
an additional strength of our study over previous studies is in our investigation of changes in calcified density of the tm .
one earlier study has reported nonquantitative changes in the prominence of tm on yearly us follow - up .
the tm was less prominent in one patient , unchanged in four , and two patients were lost to follow - up . to our knowledge , our present study is the first report to provide a quantitative analysis of calcific density in tm .
calcific density on us showed a nonstatistically significant trend toward increase over time in our study subjects .
reported a relationship between the number of microliths and testicular cancer after subgrouping subjects into four ranges based on the number of microliths . in our present study , we divided tm into two nearly equal groups based on the distribution pattern of calcification ( focal type [ 23 testes ] vs. diffuse type [ 20 testes ] ) that appear to differ in terms of calcification trends .
calcific density shows a trend toward a decrease in focal tm but toward an increase in 50% of the testes with diffuse tm .
notably , the majority of testes ( 5/8 ) in our study series with cryptorchidism , including those with bilateral cryptorchidism , were categorized as being in the increased calcification group .
during the follow - up through puberty of the microlithiasis in the 23 boys in our present study , we observed no significant changes in the density of their microliths and no development of testicular cancer ; however , we found that diffuse tm and cryptorchidism tend to increase calcific density .
hence , close observation is recommended in cases of tm combined with cryptorchidism and diffuse microlithiasis .
 purposetesticular microlithiasis ( tm ) is a relatively rare clinical entity of controversial significance characterized by the existence of hydroxyapatite microliths located in the seminiferous tubules . 
 the aim of this study was to observe the natural course of changes in the calcific density of pediatric tm.materials and methodswe included a total of 23 tm patients undergoing scrotal ultrasound ( us ) on at least two occasions from july 1997 to august 2014 . 
 we retrospectively analyzed the patient characteristics , clinical manifestations , specific pathological features , and clinical outcomes . 
 we measured the calcified area and compared the calcific density between the initial and final uss.resultsthe mean age at diagnosis was 11.34.6 years , and the follow - up period was 79.138.8 months ( range , 25.4 - 152.9 months ) . during the follow - up period , 
 no patients developed testicular cancer . 
 calcific density on us was increased in the last versus the initial us , but not to a statistically significant degree ( 3.74%6.0% vs. 3.06%4.38% , respectively , p=0.147 ) . 
 when we defined groups with increased and decreased calcification , we found that diffuse tm was categorized into the increased group to a greater degree than focal tm ( 10/20 vs. 4/23 , respectively , p=0.049 ) . 
 in addition , five of eight cases of cryptorchidism ( including two cases of bilateral cryptorchidism ) were categorized in the increased calcification group.conclusionsdiffuse tm and cryptorchidism tend to increase calcific density . 
 close observation is therefore recommended for cases of tm combined with cryptorchidism and cases of diffuse tm . 