Inguinal endometriosis: A case report

Endometriosis is defined as the presence of tissue outside the endometrium and myometrium. Usually both epithelium and stroma are seen but occasionally, only one component is present. More than 80% of all patients are in the reproductive age group with an estimated prevalence of 1-15%.[] The usual sites of involvement are the ovary and peritoneum. Noncutaneous inguinal endometriosis secondary to the involvement of the extraperitoneal portion of the round ligament occurs in <1% of all patients with endometriosis.[] The usual presentation is that of a painful, typically right-sided, hernia-like inguinal mass with exacerbation of pain and tenderness in the lump during menstruation (catamenial exacerbation) in some cases. The present case is being highlighted for its presentation at this unusual site which led to misdiagnosis. Case Report A 37 year-old gravida two, para two (G2P2) female presented to the Surgery outpatient department with a swelling in the right inguinal region. The swelling was of 5½ years' duration with associated pain and a stretching sensation that increased in intensity at times. The patient did not have this problem six years ago when she had a lower segment caesarean section for her second child. Thereafter, she noticed a painful swelling in the inguinal region within a few months of the surgery. The patient consulted a surgeon who excised the swelling. However, the excised tissue was not subjected to histopathological examination. She had some relief from pain for a few months, but was never free from it. The swelling recurred to reach the present size of 3 x 2 x 1 cm. It was a firm to hard lump in the abdominal wall in the right inguinal region, and was irreducible. A clinical possibility of a desmoid tumor was considered. The patient was referred to the Pathology department for fine needle aspiration cytology (FNAC). FNAC smears showed monolayered sheets and tightly cohesive clusters of uniform epithelial cells with bland, oval to round nuclei, scanty cytoplasm, and well-defined borders. Plump spindle cells both interspersed in these clusters and lying singly were also seen along with focal inflammatory cell infiltration, microglandular arrangement, and atypical glandular nuclei. Additionally, sheets of mesothelial cells, abundant histiocytes, and hemosiderin-laden macrophages were seen in a hemorrhagic background [Figure 1]. Ultrasonographic (USG) examination of the swelling revealed a hypoechoic, single sac-like structure that was 3.5 x 1.5 cm in size. On surgical exploration, the swelling was seen to be arising from the external oblique aponeurosis with an involvement of the round ligament. The lump was excised in view of focal atypical changes in the FNAC smears. However, laparoscopy did not reveal any other site of endometriosis. A grossly 3 x 2 x 1 cm-sized, fat-laden soft tissue piece was received for histopathological examination. The cut section showed fibrous strands and foci of hemorrhage. Microscopic examination showed endometrial tissue scattered between fibrocollagenous tissue as well as hemosiderin-laden macrophages. However, hyperplastic changes were not discernible in the glands [Figure 2].

Endometriosis is a common gynecological disease affecting women especially in the reproductive age group.[] First described by Cullen in 1896, extraperitoneal inguinal endometriosis has an incidence of 0.4%.[] It is described in most parts of the body but is uncommon in inguinal region accounting for <1% of all endometriosis patients.[] The origin of endometriosis is unknown but there are several theories to explain its pathogenesis. Vascular spread, tubal regurgitation, metaplasia of mesothelial cells, and direct extension along the round ligament from a neighboring process in the pelvis are implicated.[] It is believed that a retrograde menstrual flow (implantation theory) may cause bits of viable endometrial tissue or tubal epithelium to reflux through the fallopian tube and implant on the peritoneal surface or pelvic organs where they proliferate.[] Alternatively, it has been suggested that uterine epithelium does not escape from the tubes but that menstrual blood is capable of causing endometrial metaplasia of the peritoneum with which it comes in contact.[] The most likely pathway for endometrial tissue to implant in the superficial inguinal soft tissues is through the "Canal of Nuck," which if remaining patent, creates a communication between the peritoneal cavity and the female inguinal canal.[] In approximately 1/3rd of all reported cases, there was an associated inguinal hernia and a few had pelvic endometriosis.[] The majority of the cases are located in the right groin as was seen in our case, though the reason for this occurrence is not known.[] Preoperative misdiagnosis is often made due to the rarity of endometriosis in the extraperitoneal part of the round ligament. In the present case, it was diagnosed as a desmoid tumor due to the firmness of the lesion arising at the site of the scar. Radiological evaluation such as USG / computed tomography / magnetic resonance imaging has been reported to help in preoperative assessment by using fluctuations in tumor size with the menstrual cycle as a diagnostic aid.[] Our patient had USG evaluation only once and a definitive diagnosis was not reached. A history of cyclic pain is important in order to exclude another pathology which in our case was elicited on personal interaction with the patient during FNAC. Endometriotic lesions are easily evaluated by FNAC by looking at fragments of loosely arranged, spindled stroma, sheets of epithelial cells, and variably present, hemosiderin-laden macrophages with some cases showing mild epithelial atypia and plump stromal cells. As pointed out by Tabbara et al.,[] cytological diagnosis is to be confirmed by examining tissue in all cases, especially for malignant transformation. In conclusion, history of pain during menstruation and tenderness along with a lump is important to differentiate this condition from other inguinal pathologies. The simple, relatively atraumatic, and effective procedure of FNAC is a helpful tool for the preoperative diagnosis of endometriosis that obviates the need for diagnostic surgical procedures in some patients.

- 1. Barbieri RL. Etiology and epidemiology of endometriosis Am J Obstet Gynecol. 1990;162:565–7 - 2. Strasser EJ, Davis RM. Extraperitoneal inguinal endometriosis Am Surg. 1977;43:421–2 - 3. Metzger DA, Haney AF. Endometriosis: Etiology and pathophysiology of infertility Clin Obstet Gynecol. 1988;31:801–12 - 4. Candiani GB, Vercellini P, Fedele L, Vendola N, Carinelli S, Scaglione V. Inguinal endometriosis; pathogenetic and clinical implications Obstet Gynecol. 1991;78:191–4 - 5. Clausen I, Nielsen KT. Endometriosis in the groin Int J Gynaecol Obstet. 1987;25:469–71 - 6. Pellegrini VD Jr, Pasternak HS, Macaulay WP. Endometriosis of the pubis: A differential in the diagnosis of hip pain, A report of two cases J Bone Joint Surg Am. 1981;63:1333–4 - 7. Kernal UA, Fahri Y, Mehmet Y, Ozden K, Mehmet O. Inguinal endometriosis: A report of two cases and a review of literature Turkey J Med Sci. 2000;30:389–92 - 8. Christopher F. Inguinal endometriosis Ann Surg. 1927;86:918–21 - 9. Kirkpatrick A, Reed CM, Bui-Mansfield LT, Russell MJ, Whitford W. Radiologic-pathologic conference of Brooke Army Medical Center: endometriosis of the canal of Nuck AJR Am J Roentgenol. 2006;186:56–7 - 10. Tabbara SO, Covell JL, Abbitt PL. Diagnosis of endometriosis by fine needle aspiration cytology Diagn Cytopathol. 1991;7:606–10