GRANDROUNDS Female Runner, 47, with Inguinal Lump Libbia A. Maddox, PA-C 47-year-old woman was referred to the gyne- FIGURE cology office by her primary care NP for sur- Anatomy of the Inguinal Canal A gical excision of an enlarging nodule on the right side of her mons pubis. Onset occurred about 6 months earlier. The patient reported that symptoms waxed and waned but had worsened progressively over the past 2 to 3 months, adding that the nodule hurt only occasionally. She noted that symptoms were exacerbated by exercise, specifically running. Further questioning prompted the observation that her symp- toms were more noticeable at the time of menses. The patient’s medical history was unremarkable, with no chronic conditions; her surgical history con- sisted of a wisdom tooth extraction. She had no known drug allergies. Her family history included cerebro- vascular accident, hypertension, and arthritis. Repro- Inguinal ductive history revealed that she was G1 P1, with a ligament 38-week uncomplicated vaginal delivery. She experi- enced menarche at age 14, and her menses was regu- Pubic Superficial lar at every 28 days. For the past 5 days, there had been tubercle inguinal no dysmenorrhea. The patient was married, exercised (external) regularly, and did not use tobacco, alcohol, or illicit ring drugs. Round ligament (females)/ On examination, the patient’s blood pressure was spermatic cord (males) 123/73 mm Hg; heart rate, 77 beats/min; respiratory Illustration reprinted with permission from Austin Allen, OMS-IV. rate, 12 breaths/min; weight, 128 lb; height, 5 ft 7 in; O2 saturation, 99% on room air; and BMI, 20. The patient rupted, revealing black powdery material within the was alert and oriented to person, place, and time. She capsule. The tissue was sent for a fast, frozen section was thin, appeared physically fit, and exhibited no signs that showed “soft tissue with extensive involvement by of distress. Her physical exam was unremarkable, apart endometriosis.” The pathology report noted “[m]any from a firm, minimally tender, well-circumscribed, 3.5 endometrial glands in a background of stromal tissue. × 3.5–cm nodule right of midline on the mons pubis. Necrosis was not a feature. No evidence of atypia.” The The patient was scheduled for outpatient surgical patient’s postoperative diagnosis was endometriosis. excision of a benign skin lesion (excluding skin tags) of the genitalia, 3.1 to 3.5 cm (CPT code 11424). Dur- DISCUSSION ing this procedure, it became evident that this was not Endometriosis occurs when endometrial or “endo- a lipoma. The lesion was exceptionally hard, and it metrial-like” tissue is displaced to sites other than was difficult to discern if it was incorporated into the within the uterus. It is most frequently found on tis- rectus abdominis near the point of attachment to the sues close to the uterus, such as the ovaries or pelvic pubic symphysis. The lesion was unintentionally dis- peritoneum. Estrogen is the driving force that feeds the endometrium, causing it to proliferate, whether Libbia A. Maddox practices at Ashland Center for Women’s inside or outside the uterus. Given this dependence Health in Kentucky. on hormones, endometriosis occurs most often dur- NOVEMBER 2019 mdedge.com/clinicianreviews Clinician Reviews 11e GRANDROUNDS ing a woman’s fertile years, although it can occur af- Location ter menopause. Endometriosis is common, affecting During maturation, the parietal peritoneum develops at least 10% of premenopausal women; moreover, it a pouch called the processus vaginalis, which serves is identified as the cause in 70% of all female chronic as a passageway for the gubernaculum to transport pelvic pain cases.1-4 the round ligament running from the uterus, through Endometriosis has certain identifiable features, such the inguinal canal, and ending at the labia. After these as chronic pain, dyspareunia, infertility, and menstrual structures reach their destination, in normal develop- and gastrointestinal symptoms. However, it is seldom ment, the processus vaginalis degenerates, closing the diagnosed quickly; studies indicate that diagnosis inguinal canal. Occasionally the processus vaginalis can be delayed by 5 to 10 years after a patient has first fails to close, allowing for a communication pathway sought treatment for symptoms.2,4 Multiple factors con- between the peritoneal cavity and the inguinal canal. tribute to a lag in diagnosis: Presentation is not always This leaves the canal vulnerable to the contents of the straightforward. There are no definitive lab values or pelvic cavity, such as a hernia or hydrocele, and pro- biomarkers. Symptoms vary from patient to patient, as vides a clear path for endometriosis.5-7 The implant do clinical skills from one diagnostician to another.1 found in the case patient was at the point where the Unlike pelvic endometriosis, inguinal endometri- external ring lies, just above the right pubic tubercle osis is not common; disease in this location encom- (see Figure 1, page 11e). passes only 0.3% to 0.6% of all diagnosed cases.3,5-7 Endometriosis implants can occur anywhere along TSince the discovery of the first known case of round the round ligament in either the intrapelvic or extra- ligament endometriosis in 1896, there have been only pelvic segments. Implants have also been found in the 70 cases reported in the medical literature.6,7 wall of a hernia sac, the wall of a Nuck canal hydrocele, If the more common form of endometriosis is fre- or even in the subcutaneous tissue surrounding the quently missed, this rarely seen variant presents an inguinal canal.3 Interestingly, inguinal endometriosis even greater diagnostic challenge. The typical pre- occurs more often in the right side (up to 94% of cases) sentation of inguinal endometriosis includes a firm than in the left side, as was the case with our patient.5-7 nodule in the groin, accompanied by tenderness and The reason for this predominance has not been estab- swelling. A careful history will allude to pain that oc- lished, although there are several theories, including curs cyclically with menses. one that suggests the left side is afforded protection by the sigmoid colon.5-7 Cause Among several theories about the etiology of endo- Laboratory diagnosis metriosis, the most popular has been retrograde men- Imaging, such as ultrasound and MRI, offers some di- struation.1,4,5 According to this hypothesis, the flow of agnostic benefit, although its usefulness is most often menstrual blood moves backward through the fallo- realized in the pelvis. Pelvic ultrasound can be used pian tubes, spilling into the pelvic cavity and carrying to identify ovarian endometriomas.1 MRI can help endometrial tissue with it. One theory purports that rule out, locate, or sometimes determine the degree endometrial tissue is transplanted from the uterus of deep infiltrating endometriosis, which is an indis- to other areas of the body via the bloodstream or the pensable tool for surgical planning.5,7 Unfortunately, lymphatics, much like a metastatic disease.1,4 Another the diagnostic accuracy for extra-pelvic lesions is vari- theory states that cells outside the uterus, which line able; neither modality is particularly useful in identi- the peritoneum, transform into endometrial cells fying superficial lesions, which comprises most cases. through metaplasia.4,5 Endometrial tissue can also be Ultrasound of the groin can be employed to evalu- transplanted iatrogenically during surgery—for ex- ate for hernia; if a hernia has been excluded, histo- ample, when endometrial tissue is displaced during a logic confirmation can be obtained via fine-needle cesarean delivery, resulting in implants above the fas- aspiration of nodule contents.5,7 One caveat is that cia and below the subcutaneous layers. Several other these tests are helpful only if the clinician suspects the hypotheses concern stem-cell involvement, hormonal diagnosis and orders them. The definitive diagnostic factors, immune system dysfunction, and genetics.4,5 test remains direct visualization, which requires lapa- Currently, there are no definitive answers. roscopy.1,5 NOVEMBER 2019 mdedge.com/clinicianreviews Clinician Reviews 12e GRANDROUNDS Differential diagnosis OUTCOME FOR THE CASE PATIENT Lipoma was a favored diagnosis in this case because of The lesion was excised completely. Since the patient had the palpable, well-circumscribed borders, nontender been entirely asymptomatic until age 47, and the risks of on exam; intermittent, minimal tenderness; and no evi- a potentially unnecessary surgery outweighed the theo- dence of erythema or color change. A second possibility retical benefits, the decision was made not to perform was an enlarged lymph node, which was less likely due a diagnostic laparoscopy to investigate for pelvic endo- to the location, large size, and sudden onset without metriosis. The patient made a complete and uneventful any accompanying symptoms of infection or chronic recovery. No further treatment was initiated. She contin- illness. Finally, an inguinal hernia was least likely, again ues to be asymptomatic, denying any menstrual com- because of well-defined borders, no history of a lump in plaints, dyspareunia, or further problems with the groin. the area, a nodule that was not reducible, only minimal tenderness, and no color changes on the skin. CONCLUSION This case describes a satellite lesion of endometrial Management tissue found in an unusual location, in a patient with Definitive treatment for inguinal endometriosis en- no history, no risk factors, and no symptoms. The final tails complete surgical excision.5-7 The provider should diagnosis had been omitted from the differential— be prepared to repair a defect after the excision; there perhaps because the patient initially associated her is potential for a substantial defect that might require symptoms with exercise and mentioned the correla- mesh. Additionally, a herniorrhaphy may be indicated tion to her menstrual cycle as an afterthought. Fortu- if there is a coexisting hernia.5 The risk for recurrent nately, the correct diagnosis was made and the appro- disease in the inguinal canal after treatment is uncom- priate treatment provided.