Introduction

Endometriosis is a benign proliferative lesion in which ectopic endometrium or endometrium-like tissue is observed, and is roughly divided, accord-ing to the site of development, into internal endo-metriosis occurring in the uterus and external en-dometriosis occurring outside the uterus. Cases of endometriosis in the inguinal region are uncom-mon, accounting only for 0.8％ of all cases of exter-nal endometriosis1）. In this report, we describe a case of endometriosis in the inguinal region with a

review of the literature.

Case

The patient was an unmarried, nulliparous wom-an aged 33 years. She had noted swelling and pain in the left inguinal region for 2 years, with repeat-ed improvement and worsening of the symptoms, and presented to our hospital in suspicion of ingui-nal hernia.

A hard mass with a diameter of 10-mm was found in the left inguinal region. The mass was slightly movable, but could not be reduced by compression, which caused tenderness. Enlarge-ment of the mass and increase in pain were ob-served during menstruation. No abnormalities were found in complete blood cell counting or gen-

Abstract　A rare case of endometriosis in the inguinal region is reported.　A 33-year-old unmarried, nulliparous woman presented with a chief complaint of a mass and pain in the left inguinal region. A 10-mm mass with tenderness was noted in the left inguinal re-gion. The patient reported worsening conditions during menstruation. MRI demonstrated a 10-mm mass in the left inguinal region showing low signal intensity on T1-weighted image and high signal intensity on T2-weighted image. Surgery was performed under a diagnosis of inguinal mass with endometriosis. During surgery, a 10-mm mass was found near the external inguinal ring along the round ligament of the uterus. On pathological examination, the mass demonstrat-ed the presence of endometrial tissue and was diagnosed as external endometriosis.

　　　Key words：endometriosis, inguinal region

＊ 1） Department of Coloproctological Surgery, Juntendo University Faculty of Medicine, Tokyo, Japan

＊ 2） D e p a r t m e n t o f H u m a n P a t h o l o g y , J u n t e n d o University Faculty of Medicine, Tokyo, Japan

　　 〔Received Feb. 10, 2010〕〔Accepted Mar. 23, 2010〕

A Case of Endometriosis in the Inguinal Region

Case Report

Juntendo Medical Journal2010. 56（3）, 274〜278

Kiichi SUGiMOTO＊1）ShUn iShiYAMA＊1）MichiTOShi GOTO＊1）

YUKihirO YAGinUMA＊1）MAKOTO TAKAhAShi＊1）MASAKi hATA＊1）

hirOnObU SEnGOKU＊1）MASAnObU TAnAKA＊1）YUTAKA KOJiMA＊1）

KAzUhirO SAKAMOTO＊1）YUichi TOMiKi＊1）ATSUShi OKUzAWA＊1）

YUKi FUKUMUrA＊2）TAKAShi MATSUOKA＊2）

274

eral serum chemistry. Pelvic MRI reveals a 10-mm mass with low sig-

nal intensity on a T1-weighted image and high sig-nal intensity on a T2-weighted image was detected in the left inguinal region（Fig. 1a, b）.

During observation, pain continued to recur pe-riodically and showed no improvement. Surgery was then performed with a diagnosis of inguinal mass with endometriosis and performed according to the standard procedure for repairing inguinal hernia. After the external oblique aponeurosis was incised and the inguinal canal was opened, a 10-mm cystic mass was found near the external in-guinal ring along the round ligament of the uterus. The mass was removed and surgery was complet-ed. Cutting the removed mass revealed accumula-tion of wine-colored fluid with blood components inside the mass.

Pathological findings：Histological examination of resected specimen showed columnar epithelia with spindle-shaped nuclei were observed. The co-

lumnar epithelia were surrounded by aggregations of round cells that appeared like endometrial stromal cells （Fig. 2a）. Evidence of hemorrhage was observed in the connective tissue, suggesting the presence of intracystic hemorrhage. On immu-nohistochemistry, positive staining for estrogen re-ceptor was observed in the nuclei of the columnar epithelia and some of the surrounding stromal cells. The stromal cells were also positive for CD10 in their cytoplasm（Fig. 2b, c）. These findings led to a diagnosis of endometrial cyst arising from en-dometriosis.

The patient was discharged from hospital 2 days after surgery. On examination 2 months postopera-tively, no mass was found, but left inguinal pain coinciding with the menstrual period was ob-served. The presence of residual endometrial tis-sue was suspected. Since the pain was not as in-tense as it was before surgery and controllable with analgesics, the patient has been simply placed under observation.

Discussion

Endometriosis is a benign proliferative lesion in which ectopic endometrium or endometrium-like tissue is observed, and is roughly divided into in-ternal endometriosis occurring in the uterus and external endometriosis occurring outside the uter-us. It may cause dysmenorrhea, coital pain and in-fertility2）, and has been reported to affect 8─15％ of all fertile women3）. External endometriosis com-monly occurs in the following areas, in descending order of incidence, ovarium（38％）, pelvic peritone-um／Douglas’ pouch（21％）, rectum／colon（14％）, uterosacral ligament（8.1％）, and fallopian tube

（7.5％）, while it rarely occurs in the inguinal re-gion（0.8％）1）. The most common cause of endo-metriosis is believed to be regurgitation of endo-metrial tissue through the fallopian tube during menstruation and subsequent dissemination into the peritoneal cavity4）. Other suggested mecha-nisms include hematogenous dissemination of en-dometrial tissue5）, alteration of Mullerian duct-de-rived fetal cells6） and metaplasia of mesothelium cell7）.

The first case of inguinal endometriosis was re-ported by Cullen in 18966）. Our search of the Japa-

275Juntendo Medical Journal 56（3），2010

Figure─1　 Pelvic MR imaging reveals a 10-mm mass with low signal intensity on a T1-weighted image（a） and high signal intensity on a T2-weighted image（b） was detected in the left inguinal region（arrow）.

a

b

na Centra Revuo Medicina database with key-words “endometriosis” and “inguinal” identified 61 reports over 27 years between 1983 and 2009. Al-though it occurred in the left inguinal region in the present case, a large majority （76.1％） of the Japa-nese cases of endometriosis occurred in the right inguinal region. The most widely accepted theory for this laterality is as follows. Body fluid circulates in the clockwise direction in the peritoneal cavity and flows through the pelvic floor and the right lower abdominal region toward the head. Endome-trial tissue flowing with this fluid may be retained in the right lower abdominal region during this process8）.

Inguinal endometriosis rarely occurs in girls who have not reached menarche and postmenopausal women. It commonly manifests as a mass showing an increase in size and pain during menstruation. It is thought that the onset of inguinal endometrio-sis is preceded by pelvic endometriosis, which ex-tends through the round ligament of the uterus in-to the inguinal canal. Some cases of inguinal

endometriosis associated with inguinal hernia have also been reported9）. In the present case, although no clinical signs of pelvic endometriosis were ob-served, close examination was deemed necessary considering the possibility of later development of the condition.

For the diagnosis of inguinal endometriosis, im-aging modalities, such as ultrasonography, CT, and MRI are useful in determining the presence and location of a mass while clinical findings, such as changes in the size of the mass and the intensity of pain associated with menstruation, are impor-tant for qualitative diagnosis. Fine-needle aspira-tion cytology（FNAC） has been shown to be effec-tive for definitive diagnosis, but is also associated with the risk of causing mechanical transfer of en-dometrial tissue10）. We did not perform FNAC in the present case.

Treatment includes hormone therapy and surgi-cal therapy. The commonly used hormone thera-pies are 1） pseudo-pregnancy therapy consisting of continuous administration of estrogen and syn-

276 Goto et al：A case of endometriosis in the inguinal region

Figure─2　 Columnar epithelia with spindle-shaped nuclei were observed in the inner wall of the removed mass. The columnar epithelia were surrounded by aggregations of round cells that appeared like endometrial stromal cells

（a）（HE×200）. positive staining for estrogen receptor was observed in the nuclei of the columnar epithelia and some of the surrounding stromal cells（b）. The stromal cells were also positive for CD10 in their cytoplasm

（c）.

a

b c

thesized gestagen, 2） pseudo-menopausal therapy using gonadotropin-releasing hormone analogue, 3） gestagen therapy consisting of continuous adminis-tration of progestin and 4） danazol therapy that uses danazol that is conductor of male hormon. However, for young women who wish to be preg-nant and to have a baby, hormone therapies are not suitable and complete removal of a mass should be selected. In the present case, pain coin-ciding with menstruation period recurred 2 months postoperatively. Since no rupture of the mass occurred and complete removal of the mass was considered to be achieved during surgery, we speculated that endometrial tissue had been ex-tended to the surrounding tissues. With no means to macroscopically confirm complete removal of the mass, it is difficult to determine the presence or absence of residual endometrial tissue. Removal of a mass including the round ligament of the uter-us or surrounding subcutaneous fat may be effec-tive in preventing residual endometrial tissue.

Conclusion

We encountered and report here a case of endo-metriosis in the left inguinal region.

The possibility of inguinal endometriosis should be considered when diagnosing and treating a mass with pain coinciding with the menstruation period.

References

1） Rock JA, Markham SM：Extra pelvic endometriosis. In： Wilson EA, eds. Endometriosis. New York；Alan R Liss, 1987：185〜206.

2） Boggi U, del Chiaro M, Pietrabissa A, et al：Extrapelvic endometriosis associated with occult groin hernias. Can J Surg, 2001；44：224.

3） Licheri S, Pisano G, Erdas E, et al：Endometriosis of the round ligament ： description of a clinical case and re-view of the literature. Hernia, 2005；9：294〜297.

4） Sampson JA：Perforating hemorrhagic（chocolate） cysts of the ovary, their importance and especially their relation to pelvic adenoma of the endometrial type. Arch Surg, 1921；3：245.

5） Halban J：Hysteroadenosis metastatica（die lympho-gene genese der sog. adeno-fibromatosis heterotopica）, Wien klin. Wchnsehr, 1924；37：1205.

6） Cullen TS：Adenomyoma of the round ligament. Johns Hopkins Hosp Bull. 1896；7：112〜114.

7） Iwanoff NS：Drusiges cystenhaltiges Uterusfibromyom kompliziera durch Sarcom und Carcinoma, Monatsschr. Geburtsh u Gynaek, 1898；7：295.

8） Mashfiqul MA, Tan YM, Chintana CW：Endometriosis of the inguinal canal mimicking a hernia. Singapore Med J, 2007；48：157〜159.

9） Ogauchi Y, Endo M, Takano Y, et al：Endometriosis in an inguinal hernia sac. J Med Ultrasonics, 2000；27：1431〜1435.

10） Matsuo Y, Hayashi S, Usami S, et al：Endometriosis of the inguinal region. J Jpn Surg Assoc, 2000；61：3367〜3373.

277Juntendo Medical Journal 56（3），2010277

和 文 抄 録

　鼡径部に発生した稀な子宮内膜症の症例を経験したので報告する．　症例は未婚・未経産婦の33歳の女性．左鼡径部の腫瘤と疼痛を主訴に外来受診．左鼡径部に直径10mmの圧痛を伴う腫瘤を認め，月経時に症状の増悪を認めた．子宮内膜症を合併した鼡径部腫瘤の診断で手術を行った．手術所見では外鼡径輪の近傍に直径10mm大の腫瘤を認めた．病理組織学的検討では，組織内に子宮内膜組織が混在しており外性子宮内膜症と診断した．　　　キーワード：鼡径部腫瘤，子宮内膜症

A Case of Endometriosis in the Inguinal Region

鼡径部の子宮内膜症の1例

杉　本　起　一Kiichi SUGiMOTO

石　山　　　隼ShUn iShiYAMA

五　藤　倫　敏MichiTOShi GOTO

柳　沼　行　宏YUKihirO YAGinUMA

高　橋　　　玄 MAKOTO TAKAhAShi

秦　　　政　輝MASAKi hATA

仙　石　博　信hirOnObU SEnGOKU

田　中　真　伸MASAnObU TAnAKA

小　島　　　豊YUTAKA KOJiMA

坂　本　一　博KAzUhirO SAKAMOTO

冨　木　裕　一YUichi TOMiKi

奥　澤　淳　司ATSUShi OKUzAWA

福　村　由　紀YUKi FUKUMUrA

松　岡　　　隆TAKAShi MATSUOKA

278 Goto et al：A case of endometriosis in the inguinal region