A comparison of palpable and impalpable cryptorchid testes using CD-99 immunohistochemistry.

Objective: To compare the clinical and morphological features of impalpable and palpable cryptorchid testes, as there is debate about how much effort is appropriate to bring an impalpable undescended testicle into the scrotum.
Patients and Methods: We reviewed retrospectively 189 cases of undescended testicles in 168 patients who were explored surgically by one surgeon between August 1997 and September 2000. Operative findings of palpability, testicular size and location were collected. The mean tubular diameter (MTD), tubular fertility index (TFI) and mean number of germ cells per tubule (MGCT) were calculated using immunohistochemistry for CD-99, a Sertoli-cell marker, to classify germ cells more accurately.
Results: Sixty-three testes (33%) were impalpable; the median age at the time of surgical exploration was 23 months for both groups. The mean (sd) testicular volume for the impalpable and palpable groups were 0.83 (0.38) and 1.22 (0.54) mL, respectively. Using fitted curves of size vs age, impalpable testes were smaller than palpable testes at all ages, with the difference nearly statistically significant (P < 0.06). The MTD, TFI and MGCT decreased with age in both groups, with no statistically significant differences between the groups. A sub-analysis of abdominal and extra-abdominal testes confirmed no significant differences.
Conclusion: Impalpable testes are smaller at the time of exploration than palpable cryptorchid testes. However, histological factors predict that impalpable testes have a significant chance of future fertility and therefore orchidopexy is appropriate. CD-99 immunohistochemistry makes objective morphological information easier to obtain.