Primary extracranial meningioma of the pelvis discovered on screening pelvic examination

Abstract

Many conditions that affect a woman’s health can be evaluated through the pelvic examination. Early detection and treatment of a range of gynaecologic and non-gynaecological conditions, including unusual pelvic masses, may decrease a woman’s morbidity and mortality. Here, we have a female patient in her early 20s who was found to have a mass on her first screening pelvic examination. Subsequent imaging followed by surgical resection were performed with the final diagnosis of a pelvic meningioma. Routine pelvic examinations in asymptomatic women may be more useful than merely screening for cervical cancer and sexually transmitted infections. Once detected, the differential diagnosis of a pelvic mass may include aetiologies outside of the gynaecological organ system.

Background

Meningiomas are the most common primary tumours of the central nervous system (CNS), representing over one-third of all cases.^{1 2} Most occur intra-cranially or juxta-cranially.³ In contrast, extracranial, or ectopic, meningiomas are noted to make up less than 1% of all meningiomas.³ Though the vast majority of extracranial meningiomas occur in the head and neck,^4–9 there are rare cases reported in the literature occurring in the thoracic cavity,^10–12 carotid sinus,¹³ and kidney.¹⁴

Due to their uncommon nature, extracranial meningiomas may be a diagnostic challenge. Patients may not present with clear symptoms to suggest diagnosis. Smaller, asymptomatic tumours are unlikely to be detected unless they are noted on routine screening. In the case we present here, conducting a screening pelvic examination resulted in detection and removal of a pelvic meningioma before the patient experienced significant morbidity.

Case presentation

A woman in her early 20s presented for her first annual examination by an obstetrician/gynaecologist. She reported regular menses with menarche in her early teens. She had never been sexually active. Her medical history was significant for subclinical hypothyroidism, for which she had not required treatment. Her family history was significant for hypertension, hypothyroidism and type 2 diabetes mellitus. Her review of systems was notable only for chronic constipation. She had no specific primary symptoms at this visit. Her vitals were within normal ranges. Abdominal examination was unremarkable. On bimanual pelvic examination, there was fullness suggesting a mass effect in the right adnexa. The mass was firm but non-tender. The left adnexa was non-tender without fullness or mass. Thyroid stimulating hormone and T4 were within normal ranges. Pap smear was negative for intraepithelial lesion and malignancy.

Investigations

A pelvic ultrasound (figure 1) was obtained and was equivocal, demonstrating no clear mass. MRI of the pelvis with and without contrast (figures 2 and 3) was obtained for further evaluation and demonstrated a 9.5×5.6 cm, heterogenous, contrast enhancing, right adnexal mass. The mass was located to the right of the midline in the pelvis at the level of the sacral promontory. It approximated but did not definitely arise from the right ovary. CA-125 level was obtained and normal at 5.

Figure 1.

Pelvic ultrasound was notable for considerable gas in the colon of the right lower quadrant. There was significant shadowing from the pelvic mass.

Figure 2.

MRI (axial T1 postcontrast image with fat suppression).

Figure 3.

MRI (T2-weighted coronal image).

Differential diagnosis

The differential diagnosis for a pelvic mass is broad and includes but is not limited to infectious causes, benign and malignant masses originating from gynaecological organs, masses from surrounding tissues, like colon, and simple or complex cysts.¹⁵ Our patient’s mass was firm and non-tender. She had no fevers. She was young at the time of diagnosis, which decreased her risk of malignancy. She did not have any abdominal bloating, abnormal uterine bleeding, early satiety, change in bowel or bladder habits, or pelvic pain or pressure, which are signs which may be more concerning for malignancy. She did not have a history of neurofibromatosis type 2 or radiation therapy, both of which increase the risk of meningiomas.^{16 17} In a young, premenopausal, asymptomatic female, the presentation was most consistent with an extrauterine leiomyoma or possible mature cystic teratoma.

Treatment

Following a discussion between the patient, obstetrics and gynaecology, oncological surgeons, and gynaecological oncology physicians, the decision was made to proceed with exploratory laparotomy for removal of the mass. Intraoperative findings demonstrated a firm, calcified mass which abutted the sacral promontory but did not appear to invade or arise from the periosteum (figures 4–6). The right ureter ran over the surface of the mass. The mass was confirmed to be separate from the right ovary. Operative findings were not increasingly concerning for malignancy, as there was only a single tumour and the peritoneal surfaces were smooth and without nodularity. There was no ascites. The pelvic organs were all visually normal on exploration.

Figure 4.

Intraoperative picture from midline incision on lower abdomen showing retroperitoneal firm mass.

Figure 5.

Pelvic mass after excision.

Figure 6.

Tumour prior to removal.

Pathology and histology

Gross pathology demonstrated a tan-pink, partially encapsulated, extensively calcified tumour measuring 11.5×8.0×6.5 cm. De-calcifying solution revealed heterogenous tan-yellow-brown areas.

It was difficult to discern if the tumour developed from the middle (arachnoid) layer of the meningeal membrane covering of the spinal cord or from the Schwann cells, which are cells that form myelin, the insulating layer around the peripheral nerves. Microscopic sections demonstrated an extensively calcified and hypocellular tumour (see figures 7–9). Areas between the calcospherites showed round/ovoid to slightly spindle neoplastic cells, arranged in small sheets or lobules, with moderate amount of indistinct, palely eosinophilic cytoplasm and bland nuclei. Characteristic tight whorls or intranuclear pseudoinclusions were not seen. There were large numbers of variably sized psammomatous calcifications. Mitoses were not present. Necrosis was not identified.

Figure 7.

10× view demonstrating psammoma bodies (arrows).

Figure 8.

4× view demonstrating highly calcified tumour (arrows indicating calcifications).

Figure 9.

4× view, positive S-100 staining (red arrow), significant calcifications present (blue arrow).

At our institution, the tumour was focally positive for S100 and CD99. Immunostaining for CD68 was diffusely positive. Immunostaining for epithelial membrane antigen (EMA) was negative. Rare tumour cells were positive for periodic acid-schiff. No staining was seen with keratin, inhibin, vimentin, melan A, HMB45, GFAP, SMA, desmin, chromogranin, synaptophysin, NSE, CD57, calretinin, HAM56, CD1a and p53. Immunostaining for ki-67, a proliferation marker, showed low activity. All controls showed appropriate staining. Given S-100 positivity and spindle neoplastic cells, diagnostic considerations included a schwannoma or meningioma.

The specimen was sent to Brigham and Women’s for consultation. Immunostaining there demonstrated multifocal positivity for EMA while pan-keratin, CAM 5.2, S-100 and claudin were negative. Staining for CD163, a marker of monocytic/histiocytic lineage, only highlighted stromal macrophages. The consulting pathologist described findings to be in line with a calcified, psammomatous meningioma.

Following consultation, our final diagnosis was recorded as a WHO Grade 1 extensively calcified psammomatous meningioma of the type most often seen arising in spinal meninges.

Outcome and follow-up

Following final diagnosis of the tumour, consultation was made with a neurosurgeon. Grade 1 meningiomas are the most common classification of meningiomas, and they are considered noncancerous. It was recommended that the patient have a postoperative MRI and CT scan with follow-up MRI again 4 months after surgery. As she did not demonstrate signs of CNS disease (back pain, radicular pain, headache), CNS imaging was not recommended. The mass in her pelvis was considered a primary extracranial meningioma. She was followed for several years postoperatively with annual, screening MRIs. No further tumours were noted. She has been healthy and asymptomatic for 14 years, without a known recurrence.

Discussion

Our patient presented to an annual well-woman visit with no evident symptoms and was discovered to have a pelvic mass on screening bimanual pelvic examination. We are aware of only two other reported cases of pelvic meningiomas, both occurring in postmenopausal females.^{18 19} In each case, the patients had previously undergone hysterectomy with bilateral salpingo-oophorectomy. To our knowledge, this is the first pelvic meningioma reported in a pre-menopausal woman.

In March of 2017, the US Practice Advisory Task Force concluded that there was insufficient evidence in the literature to adequately weigh the benefits and harms of the screening pelvic examination in asymptomatic, non-pregnant women.²⁰ Due to the low population prevalence of ovarian cancer, there are low positive predictive values and high false-positive rates for ovarian cancer from screening pelvic examinations. Surgery rates from abnormal examinations range from 5% to 36%.²⁰ In an effort to do no harm, the American College of Physicians strongly recommends against pelvic examinations in asymptomatic women, stating no evidence of benefit.²¹ The American College of Ob-Gyn, however, recommends that pelvic examinations be offered to asymptomatic, non-pregnant women after informed discussion between the patient and their healthcare providers.²² In our case, the benefits of a pelvic examination became clearer when a pelvic mass was palpated, allowing for early detection and treatment. More research is needed to assess the effectiveness of screening pelvic examinations, to make a more conclusive recommendation for or against them in the future.²⁰

Tumours originating outside of the gynaecological system should be considered in the differential diagnosis of a pelvic mass. Rare tumours may be locally aggressive, and growth can cause serious morbidity or even mortality. In our case, the tumour was a benign pelvic psammomatous meningioma, although schwannoma remained on the differential until outside pathology consultation was completed. In some cases, MRI features can help differentiate schwannomas from meningiomas. Spinal schwannomas are more likely to show more cystic changes, lumbar location, and neural foraminal extension, whereas meningiomas are more commonly in the thoracic location, smaller in size and commonly have a thickening of the dura immediately adjacent to the mass called a ‘dural tail sign’.²³ Meningiomas are the most common CNS tumours, and they rarely arise outside of the central neural axis.²⁴ They are typically slow-growing and often asymptomatic.²⁵ Histologically, it can be difficult to diagnose meningiomas that arise in uncommon, extracranial locations.

Classically, the most common positive immunohistochemistry markers for diagnosing meningiomas are EMA and progesterone receptors.²⁴ However, sensitivity of these two older markers is low and can vary depending on the grade and/or type of meningioma.²⁴ Somatostatin receptor 2A (SSTR2A), a newer marker which was not used in our case which presented roughly 14 years ago, was shown to be the most sensitive and specific marker for a meningioma in a study by Boulagnon-Rombi et al. In this study, combining SSTR2A and EMA was effective in detecting all meningiomas.²⁴ In addition, SOX10 was the most sensitive and specific marker for differentiating the schwannoma from the meningioma.²⁴

In our young patient, a benign pelvic mass was the more likely outcome. In a patient of any age, however, a pelvic mass should be explored for possible signs of malignancy. Key imaging features can be used to distinguish malignant from benign pelvic masses. Ultrasound imaging with doppler blood flow analysis can help successfully characterise 90% of masses as benign or malignant.²⁶ Mass characteristics which increase the probability of malignancy include papillary excrescences measuring 3 mm or larger, thick septations, irregular margins, peritoneal nodules, or ascites.²⁶ When ultrasound is indeterminant, as in our case, MRI may be obtained, as the overall accuracy for characterising a malignant or benign condition is 93% with MRI.²⁶

The prognosis for primary extracranial meningiomas, which account for <1% of all meningiomas, is excellent. At 5 years, 82% of patients are disease free, and at 10 years 78% are free of disease.¹⁹ The prognosis relates directly to the extent of resection.²⁷ In our case, the tumour was completely resected, and the patient has been disease free for many years. This is a case where a screening pelvic examination in an otherwise asymptomatic, non-pregnant female proved to be beneficial.

Any identifiable patients have provided their signed consent to publication and submit, as a supplemental file, The BMJ’s patient consent form.

Learning points.

• Screening pelvic examinations may be beneficial in otherwise asymptomatic non-pregnant patients, as they have the potential to detect disease early in its course.

• While ultrasound is a useful tool for the assessment of pelvic masses of gynaecological origins, additional imaging modalities, specifically MRI, may be necessary for complete assessment of pelvic masses.

• An extracranial (ectopic) meningioma arising in the pelvis is a rare entity, with only two other cases we are aware of reported in the literature to date, this being the first occurring in a premenopausal female.

• Newer immunohistochemical markers (SSTR2A, STAT6, SOX10) can help differentiate between meningiomas and other tumours that mimic them.

Ethics statements

Patient consent for publication

Consent obtained directly from patient(s).