paratesticular embryonic remnants

The normal development of the male genital tract is the result of the differentiation of wolffian derivatives and the involution of müllerian derivatives.

Wolffian remnants and Mullerian remnants are frequently observed in autopsies of
fetal and postnatal cases, and they sometimes persist in adult men.

In adults, these embryonic remnants usually are an incidental finding in surgical specimens and rarely undergo proliferative changes.

Their most frequent pathologic characteristic is the adoption of a cystic pattern in epididymal and testicular hydatids.

In addition, some cases of testicular albuginea cysts and 30% of all spermatic cord cysts are considered to be derived from embryonic remnants.

The most frequent testicular and paratesticular cysts are unicavity or multicavity cysts, lined by a cubic epithelium. These simple cysts frequently are derived from the mesothelium.

Most paratesticular embryonic remnant cysts remain asymptomatic for a long time but occasionally can become large and undergo torsion, which manifests clinically as an acute scrotum.

Epithelial proliferations in these embryonic remnants are rare. A few cases of malignant transformation of embryonic remnants have been reported in the appendix testis, including cases of adenocarcinoma, cystadenocarcinoma, and a low malignancy müllerian-type epithelial tumor.

Other paratesticular tumors that might develop from embryonic remnants have been described, such as papillary serous cystadenomatous tumor, which exhibits a low malignant potential; 1 case of borderline paratesticular tumor diagnosed as cystadenoma of the spermatic cord, which histologically resembles an ovarian serous epithelial tumor of low malignant potent; 2 cases of spermatic cord cystadenoma; and a peculiar epididymal spermatocele with mural papilloma.

Three types of cysts with benign epithelial proliferations (BEPs) were considered:
 (1) cystadenomas with a papillary or a cribriform pattern;
 (2) papillomas, urothelial and mural;
 (3) wolffian hamartomas.

To distinguish between these embryonic origins, CD10 antigen, a metalloendopeptidase typically positive in wolffian mesonephric and intestinal derivatives, was evaluated in all paratesticular cysts with BEPs.

Types

 paratesticular Mullerian remnant
 paratesticular Wolffian remnant

References

 Paratesticular cysts with benign epithelial proliferations of wolffian origin. Nistal M, González-Peramato P, Serrano A, Vega-Perez M, De Miguel MP, Regadera J. Am J Clin Pathol. 2005 Aug;124(2):245-51.PMID: 16040296