Endometriosis-associated hydrocele of the canal of Nuck with immunohistochemical confirmation: a case report

Abstract

Background: The canal of Nuck is an embryological vestige of the processus vaginalis, and presents a potential site for endometriosis seeding. Hydroceles in this region are a rare cause of inguinal swelling in females. In addition, endometriosis localized to the canal of Nuck is exceedingly rare.

Case presentation: A 44-year-old Japanese woman presented with a painful mass overlying her right pubis. She underwent surgery to completely excise the mass. During surgery, division of the external oblique aponeurosis revealed a cyst that occupied the inguinal canal and it adhered to the transverse fascia, inguinal ligament, and pubic bone. The cyst was dissected from the round ligament, and the defect in the internal inguinal ring was repaired and reinforced with mesh. On macroscopic examination, the cyst had a heterogeneous fibrous aspect with dark brown inclusions. Microscopic examination revealed that the cyst was tortuous, lined by mesothelial-like cells, and accompanied by partial subcapsular hemorrhage. Endometrium-like tissue was observed in the cystic wall. Immunohistochemical staining for podoplanin confirmed the mesothelial origin of the cyst-lining cells. The epithelial cells and stromal cells were positive for estrogen receptors.

Conclusions: In this case of an endometriosis-associated hydrocele of the canal of Nuck, the mesothelial origin of the cyst-lining cells and endometriosis were confirmed by positive immunohistochemical staining for podoplanin and estrogen receptors, respectively. We determined that hydrocele resection and reinforcement of the anterior inguinal canal wall (if necessary) are appropriate treatments for this condition.

Keywords: Endometriosis; Estrogen receptor; Hydrocele of the canal of Nuck; Podoplanin.

Fig. 1

Computed tomography scans showing a round cystic lesion (arrow) within the right inguinal canal. a Transverse image. b Sagittal image. c Frontal image

Fig. 2

Intraoperative findings showing that the cyst, which contained dark brown fluid, strongly adhered to the round ligament of the uterus

Fig. 3

Histological examination of the excised cyst. a The cyst was tortuous (hematoxylin and eosin staining; low magnification). b Tissue is evident, but the cyst-lining cells are unclear; endometrium-like tissue is observed in the cystic wall (hematoxylin and eosin staining; high magnification). c Podoplanin-positive cyst-lining cells are clearly observed after immunohistochemical staining (immunoperoxidase stain with hematoxylin counterstain; high magnification). d Epithelial cells and stromal cells are positive for estrogen receptors after immunohistochemical staining (immunoperoxidase stain with hematoxylin counterstain; high magnification). b, c, and d are magnified images of the area within the frame in (a)