[Macro-orchidism: new pathogenetic and histopathologic aspects].

Macro-orchidism (MO) is the increase of the testicular volume, up to 25 ml in the adult male. It is frequently associated with mental retardation (MR) with fragile X-chromosome (FXC) (Martin-Bell syndrome). Sometimes it is of unknown origin and is called "benign idiopathic macro-orchidism" (BIMO). MO has also been described in association with bilateral testicular tumors, idiopathic precocious puberty, juvenile hypothyroidism and, more rarely, with congenital testicular cysts (cystic testicular dysplasia) and testicular microlithiasis in a patient treated with GH. The most common presentation is MR associated with MO, with positive or negative FXC. Among MO with MR and FXC-marfanoid habitus patients have been described and in the Atkin-Flaitz syndrome patients. Management of MO must be conservative in all cases and testicular biopsy must only be performed to diagnose leukemic infiltration or carcinoma in situ (CIS), or as the last fertility diagnostic test in BIMO. A wide range of primary testicular lesions may histopathologically be found: preserved spermatogenesis tubes, only Sertoli cell pattern and complete tubular sclerosis. Interstitial edema, frequently implicated in the MO pathogeny, does not explain by itself the important increase in testicular volume. In our laboratory, we have demonstrated that the increment of the testicular volume in MO is associated with a significant increase in the length of the seminiferous tubules. MO may pathogenically be intimately related to some hormonal regulation mechanism or to a higher seminiferous tubule sensitivity to FSH.