Incidental appendiceal mass as the only manifestation of endometriosis

Abstract

Appendiceal endometriosis is a rare condition that remains difficult to diagnose preoperatively. Herein, we present a case of appendiceal endometriosis presenting as a neuroendocrine tumor. A 34-year-old Caucasian woman was found to have an appendiceal mass with a small fluid collection on routine transvaginal ultrasound. The patient denied any symptoms. Features were consistent with those of a neuroendocrine tumour of the appendix. Laparoscopic appendectomy followed by histopathology revealed endometriosis with negative cytology for malignant cells. Preoperative characteristics of appendiceal tumours in women of childbearing age should be further investigated. Establishing clinical and surgical guidelines is the key to avoid invasive procedures and related adverse outcomes.

Background

Endometriosis is a condition that affects 10%–15% of reproductive-aged women^{1 2} and can manifest in several locations.³ Appendiceal endometriosis is a rare condition with a prevalence of 0.4% among the general population.⁴ The manifestations of endometriosis in the gastrointestinal tract are mostly asymptomatic. Preoperative diagnosis remains difficult, as there are no reported gross or radiological features that describe appendiceal endometriosis.

We report a case of appendiceal endometriosis that was mistaken for a neuroendocrine tumour (NET) of the appendix. The appendiceal mass was discovered incidentally. The size, position and patient demographics were consistent with a diagnosis of NET of the appendix. The presentation as an incidental finding additionally supported NET as a diagnosis.

This case demonstrates the need for preoperative characterisation of appendiceal tumours in women of childbearing age. Additionally, it brings forward an appendiceal mass being the only manifestation of endometriosis in a patient.

Case presentation

A healthy 34-year-old G2P2 Caucasian female patient presented to our institution for a routine gynaecological check-up. She had no reports and was feeling well. Her last menstrual period was 18 days ago, as per her normal cycle and her last gynaecological consultation 15 months ago had been unremarkable. On examination, the patient was normotensive with a blood pressure of 115/64 and a pulse of 91. A bimanual examination revealed a normal-sized anteverted uterus and normal adnexa. Transvaginal ultrasound (TVUS) revealed a right adnexal mass with some fluid around it.

Review of systems was unremarkable. The patient denied any recent unintentional weight loss, atypical fatigue or any systemic symptom. She also denied any flushing or skin rash. She reported normal bowel movements, and the absence of abdominal distention, bloating, early satiety or nausea and vomiting.

A review of the patient’s menstrual history revealed menarche at age 12 years, and a cycle length of 29–31 days with 6 days of moderate flow. She reported suffering from moderate dysmenorrhoea on the first day of her menses, relieved by use of ibuprofen. She was sexually active in a monogamous relationship with her husband. The patient gave birth to the couple’s first child 4 years ago, at age 30 years, after an uneventful term pregnancy. She gave birth to their second child 2 years later, 18 months prior to presentation. She breast fed both babies for 10 months.

The patient has never used hormonal contraception, and the couple currently uses barrier contraception for birth control. Medical history is insignificant, apart from a keloid at a piercing site. Surgical history was negative. She reported being an ex-smoker and not drinking alcohol. She had a healthy body mass index of 24.8 kg/m² at the time of presentation and described her lifestyle as sedentary.

Her family history is significant for diabetes and heart disease. Her mother has never had abdominal surgery, and she has no sisters.

On examination, the patient was normotensive with a blood pressure of 115/64 and a pulse of 91. Physical examination was unremarkable. Abdominal inspection revealed a symmetrical non-distended abdomen, with no scars or protrusions. Auscultation revealed normal bowel sounds. No pain, rebound tenderness or guarding was elicited by superficial or deep palpation. The abdomen was soft and no masses were felt. The liver and spleen had normal contours. McBurney’s sign, Rovsing sign and psoas sign were all negative.

Investigations

Following this finding on TVUS, contrast-enhanced CT scan of the abdomen and pelvis demonstrated normal ovaries/uterus and an incidental appendiceal mass (1.5×1 cm), confined to the tip of the appendix (figure 1). The remainder of the appendix was unremarkable. A small volume of fluid in the pelvis and along the right paracolic gutter was also noted. Differential diagnosis of NET, dense mucocele and appendiceal cancer was made, with NET being the most probable.

Figure 1.

(A) Axial and (B) coronal images of a contrast-enhanced CT of the abdomen and pelvis (slice thickness: 3 mm, Kvp: 120, uAs: 72) showing a well-defined soft tissue lesion at the tip of the appendix measuring 1.5×1.0 cm with a CT density of 64 HU. No soft-tissue thickening or border irregularities can be seen. No peri-appendiceal inflammatory changes. No enlarged lymph nodes in the abdomen or pelvis, in particular in the right lower quadrant. Normal liver morphology and enhancement are noted. No liver nodules are seen. Normal calibre intrahepatic and common bile ducts. Normal morphology of the stomach and duodenum. Normal calibre small and large bowel. No lesions suggestive of distant metastasis can be noted elsewhere in the abdomen or pelvis.

Tumour characteristics on imaging and the patient’s demographics were the main factors that determined that a NET of the appendix is the most plausible diagnosis.

In the absence of symptoms suggestive of carcinoid syndrome, serum levels of chromogranin-A (CgA) and urine levels of 5-hydroxy-indole-acetic acid (5-HIAA) were not ordered. A colonoscopy to investigate the presence of NET lesions in the gastrointestinal tract was also not performed. Additional work-up for appendix cancer was also not performed, due to the small size of the patient’s mass and lack of signs suggestive of peritoneal and/or liver spread, as an appendectomy is deemed curative in this case.

Treatment

The patient was referred to the department of surgery for further management. Following discussion during our multidisciplinary meeting, surgical resection of the appendix was deemed to be the appropriate course of action.

A laparoscopic appendectomy was thus performed. Careful dissection of the appendix and mesoappendix was performed and included all mesenteric lymph nodes. The appendix was placed in an EndoBag and removed through the umbilical incision. No perforation, spillage or rupture occurred. The appendix specimen was red in colour. It had smooth borders and showed a thickened tip. No signs of inflammation were seen (figure 2). Minimal appendiceal stump was left in place and a fluid sample was extracted from the pelvis.

Figure 2.

The appendix measures 3.5×0.8×0.7 cm. The serosa is smooth and shiny. The distal 1.5 cm of the appendix is curved and thickened. The distal tip also shows fibrotic puckering. No signs of appendicitis or inflammation can be seen.

A careful intraoperative examination of the abdomen and pelvis under direct visualisation did not reveal any notable findings. The entire small bowel was examined during the operation and revealed a normal smooth contour with no lesions. The peritoneal cavity was inspected. No omental bleeding or masses were noted. No adhesions were seen, consistent with the patient’s negative surgical history. Inspection of both ovaries, the tubes, the uterus and the pelvis was performed, and revealed normal findings. No endometriomas were noted at the time.

Outcome and follow-up

Final pathology revealed endometriosis with negative cytology for malignant cells.

The patient was seen for follow-up 6 weeks after her surgery. Her postoperative course was unremarkable. The patient denied any symptoms of endometriosis.

She followed up with her gynaecologist after her surgery and diagnosis. She was offered multiple options to decrease recurrence of her endometriosis, such as oral contraceptives or a hormonal intrauterine device (IUD). She also received counselling regarding the benefits of exercise. She however decided not to undertake any treatment at that moment as she and her husband wish to have another baby soon. She however expressed interest in placing a hormonal IUD after giving birth to a third child.

Discussion

Appendiceal tumours are very rare and classically diagnosed incidentally in approximately 1% of all appendectomies.⁵ Despite accounting for only 0.4% of gastrointestinal malignancies, appendiceal neoplasms have diverse histology. NETs, also known as carcinoid tumours, are the most common subtype and represent up to 85% of all appendiceal neoplasms,^{5 6} with lesions characteristically occurring at the tips of the appendix.^{7 8} They are followed in prevalence by mucinous neoplasms and adenocarcinomas.⁹ Most appendiceal tumours are diagnosed in older adults with a mean age of diagnosis ranging between 55 and 66 years old, to the exception of NETs that present earlier, between 32 and 42 years old.^{10 11} Additionally, NETs have female predominance^{11 12} and often appear as small (<1 cm) round masses confined to the distal appendix⁵ on CT,¹³ similarly to our patient’s presentation (figure 1). Diagnostic tests such as CgA and 5-HIAA have a low accuracy in localised and non-functional disease,^{14 15} such as our patient’s. Colonoscopy is also of limited diagnostic value in this case, as appendiceal NETs have a low metastatic potential and imaging showed mass confinement to the tip of the appendix and absence of lymph node involvement.¹⁶ Hence, preoperative diagnosis of appendiceal NETs is difficult, and histopathology remains the definitive diagnostic technique.

As per the European Neuroendocrine Tumor Society guidelines,¹⁷ laparoscopic appendectomy with lymphadenectomy was the procedure of choice, given the size and intraoperative appearance of the tumour, which had a size of 1–2 cm and showed no adhesions or nodules and no lymphatic spread or lymph node involvement.

Appendiceal endometriosis is a very rare condition with a prevalence of 0.4% in the general population.⁴ Our patient did not report any abdominal pain, chronic pelvic pain, menstrual irregularities or infertility.¹⁸ Additionally, surgical exploration did not reveal intraoperative findings consistent with endometriosis, such as adhesion of the appendix to the sidewall or ovaries or visible endometriosis lesions on the rest of the gastrointestinal tract. The way our patient presented was thus not consistent with a clinical picture of appendiceal endometriosis but one of appendiceal NETs.

The preoperative characteristics of appendiceal tumours in women of childbearing age have not been specifically addressed in the literature and there is no consensus on the management of such tumours in this category of patients.¹⁹ Appendiceal endometriosis may reach several centimetres in size.^20–26 Preoperative diagnosis is difficult (MRI, which has a low sensitivity of 33% in gastrointestinal endometriosis²⁷) and laparoscopy followed by histopathological examination remains the definitive diagnostic tool.²⁸

To our knowledge, there is no reliable way to identify appendiceal endometriosis preoperatively. In summary, it is important to further investigate the preoperative characteristics of appendiceal tumours in women of childbearing age, notably appendiceal endometriosis, and further studies are required in order to avoid unnecessary invasive procedures.

Learning points.

• Appendiceal endometriosis may present similarly to a neuroendocrine tumour.

• Appendiceal endometriosis may present as an isolated finding of endometriosis.

• There is a gap in the literature regarding the preoperative characteristics of appendiceal tumours in women of childbearing age.