Penislike clitorises with megalourethras in nonvirilized female fetuses and a newborn. A histopathologic study and its bearing on their pathogenesis.

Objective: The aim of the study was to analyze the microstructure of penislike clitorises in female pseudohermaphroditism in relation to their pathogenesis.

Methods: Penislike clitorises from 2 fetuses and 1 newborn with anorectal malformations and multiple other caudal anomalies and 1 fetus with phallic urethra duplication were histologically examined in toto.

Results: The penislike clitorises revealed basically female features in the histogenesis of the corpora cavernosa and glans and in the absence of penile raphe, septum, fasciae, and periurethral glands. In 2 cases, the "phallic urethra" was completely surrounded by a single corpus cavernosum and in 3 cases by a circular glans. Labia minora and vestibular bulbs had not developed in 3 cases. The urethras had transformed into fusiform or scaphoid megalourethras with stenotic meatuses in 3 specimens and an extra orifice in the fourth specimen.

Conclusions: Penislike clitorises in female pseudohermaphroditism show a fundamental dysgenesis of major structural elements. The pattern favors the hypothesis of an early error in the formation of the cloacal membrane and adjacent cloaca in embryos between 26 and 29 days postovulation that may lead to dysregulation of molecular developmental interactions during the following formation of the genital tubercle.