Nuck canal cyst: use of immunohistochemistry to reveal vestigial endometriosis hidden within mural granulation tissue

A case of a Nuck canal cyst (NCC) associated with vestigial endometriosis is presented. An ultrasound scan revealed a multicystic sac in the right groin of a 42-year-old woman who had experienced inguinal discomfort for over 5 years. A Marcy repair was performed on the inguinal lesion based on the clinical diagnosis of an inguinal hernia. The resected multicystic blind tube had a small protruding nodule on the cyst wall. Although this nodule was initially thought to be granulation tissue, detailed high-power histological examination revealed severely degenerated residual glands that could not be characterised further using haematoxylin and eosin staining. Immunohistochemical staining revealed that the glandular epithelial cells were oestrogen receptor positive, while the background stromal cells were CD10 positive. A diagnosis of NCC with endometriosis was made. A review of the relevant literature concerning the complication of the NCC and the usefulness of immunohistochemical staining is also included.