A case of ependymoma arising from the peritoneum

Abstract

Ependymoma arising from the peritoneum is extremely rare. We present the case of a 23-year-old woman who underwent urgent laparoscopic surgery because of a pelvic mass and intraperitoneal bleeding. Although peritoneal carcinoma was suspected, pathological re-examination revealed ependymoma with a perivascular pseudorosette and positive for glial fibrillary acidic protein. Residual tumor extraction indicated that the ependymoma had developed from the peritoneum. This case highlights the need to consider ependymoma as a potential diagnosis in young women with suspected ovarian or peritoneal cancer.

Introduction

Ependymoma is defined as a tumor comprising neoplastic ependymal cells. It is a type of glioma that develops from central nervous tissue, such as the wall of the cerebral ventricle or central canal of the spinal cord. Ependymomas accounts for 3–5 % of all gliomas. Although the ovary and peritoneum have been reported as sites of origin for ependymomas, such cases are extremely rare and the clinical characteristics are unclear. We report an unusual case of ependymoma arising from the peritoneum.

Case report

A 23-year-old Japanese woman with no significant past medical or familial history presented to the emergency department of her previous hospital with complaints of abdominal pain, fever elevation, and vomiting. Computed tomography (CT) and magnetic resonance imaging (MRI) revealed a pelvic mass and intraperitoneal bleeding (Fig. 1). The patient underwent urgent laparoscopic surgery. A clot and ruptured soft tumor mass were observed in the anterior wall of the uterus, pouch of Douglas, and great omentum. No macroscopically abnormal findings were observed in the bilateral adnexa. Pathological examination suggested adenocarcinoma, and she was therefore referred to our cancer center with suspicion of peritoneal cancer.

Fig. 1.

MRI at patient’s previous first hospital visit. A solid lesion wrapped in a capsule-like structure was detected in the uterus ventral and dorsal aspects

We detected masses around the right adnexa and pouch of Douglas based on the original MRI results, and abnormal shadows close to the liver margins were revealed by CT and fluorodeoxyglucose positron emission tomography–CT (Fig. 2a, b). Blood biochemistry results showed slightly elevated CA125 levels (53.2 U/ml; normal, 0–35 U/ml). Serum levels of CA19-9, carcinoembryonic antigen, and α-fetoprotein were within normal ranges. The previous diagnosis was suspicious of serous carcinoma arising from the peritoneum (Fig. 3). However, we suspected ependymoma based on the detection of a perivascular pseudorosette structure (Fig. 4) comprising cytoplasmic processes surrounding a small vessel by hematoxylin and eosin staining of tissue sections. Immunohistochemical staining was positive for glial fibrillary acidic protein (GFAP) in the cytoplasm of the tumor cells (Fig. 5), confirming the diagnosis of ectopic ependymoma. Immunohistochemistry also revealed positivity for vimentin, CD56, S-100, WT-1, estrogen receptor (ER), and progesterone receptor (PgR) (Table 1). No central nervous system abnormality was detected by cephalic imaging study. We made a final diagnosis of ependymoma arising from the peritoneum. Debulking surgery was planned involving residual tumor enucleation, because the patient wanted to preserve her fertility potential. Dissemination throughout the pelvic floor and a grayish-white papillary mass stemming from the retroperitoneum on the underside of liver were noted during laparotomy (Fig. 6). Her bilateral ovaries were macroscopically normal, but some miliary peritoneal lesions remained in the peritoneal pouch of Douglas. We suggested adjuvant chemotherapy, but the patient refused. No tumor progression was detected at 10 months after surgery.

Fig. 2.

a CT showed a soft, abnormal shadow close against the liver S6 margins. b Postoperative PET-CT showed light fluorodeoxyglucose accumulation in these sites (SUVmax = 2.6)

Fig. 3.

Histologic findings demonstrated similar morphology to serous carcinoma at the initial laparoscopic surgery (papillary growth and psammoma body). a Hematoxylin and eosin (HE) ×200, and b HE ×40

Fig. 4.

Perivascular pseudorosette. a HE ×200, and b HE ×400

Fig. 5.

Immunohistochemical findings indicating GFAP positivity (×200)

Table 1.

Immunohistochemical staining

Antibody
GFAPa	+
Vimentin	+
CD56	+
S-100	+
p53	−
WT-1	+
Keratin7	(−)/p(+)
Calretinin	−
ER	+
PR	+
MIB-1 index (%)	5–20 %

^a GFAP Glial fibrillary acidic protein

Fig. 6.

a Laparotomy findings. The mass developed from the retroperitoneum on the underside of the liver. b Macroscopic appearance. The tumor was a grayish-white papillary mass

Discussion

Ependymoma arising from the peritoneum is extremely rare, with only 17 case reported in Japan since its first record by Kleinman et al. in 1984 [1]. Although ependymomas occurring outside the central nervous system were classified as ‘monodermal and highly specialized teratomas’ according to the previous WHO classification [2], they are currently classified under miscellaneous tumors and ‘tumors of the broad ligament and other uterine ligaments’ in the 4th edition [3]. No macroscopic neoplastic lesions were found in either ovary in the current case, and the tumor was determined to have arisen from the peritoneum.

Ependymomas developing from the abdominal cavity are most common in women of reproductive age (mean age 35 years), and there have been no reported occurrences in men [4]. Ependymomas comprise a nodular mass with a mix of solid and cystic parts, sometimes with bleeding and necrosis, based on imaging examinations. Specific imaging findings of ependymoma in abdominal cavity have not been reported. Although positron emission tomography/computed tomography (PET/CT) findings have not been reported, our case indicated low fluorodeoxyglucose (FDG) uptake at tumor. Ependymoma arising from the peritoneum may have a low maximum standardized uptake values (SUVmax) level of PET/CT compared to common peritoneal cancer.

Tumor growth is relatively slow. Duggan et al. reported no correlation between mitotic rate and prognosis, and suggested that tumor diameter was associated with risk of metastasis and recurrence [4]. There are a few case reports of recurrence, however, in most of those cases, the time to recurrence is several years (0.5–30 years, median 4.75 years) [5]. Since late recurrence is also reported, careful long-term surveillance of the patients is required [3]. In terms of treatment, surgical resection is considered to be important, but the value of postoperative chemotherapy has not been established. Although there have been several reported cases of the use of chemotherapy with cisplatin, and combination chemotherapy with bleomycin, etoposide, and cisplatin (BEP). However, Takano et al. reported that these treatment preferences were based on germ cell tumors [5].

Some disseminated lesion remained after debulking surgery in the current case because of the patient’s wish to preserve her fecundity. However, although we performed conservative surgery, there is currently no evidence of her prospects for pregnancy, and if the residual tumor subsequently grows or metastasizes, more radical therapies may be required, despite the patient’s preferences.

The pathological findings of ectopic ependymoma are similar to those of ependymoma of the central nervous system. Jacket rosette, perivascular pseudorosette, and an ependymal canal are characteristic, together with GFAP positivity on immunohistochemistry. If the site of origin is in the central nervous tissue, the diagnosis of ependymoma is relatively straightforward; however, in the case of an intraperitoneal origin, the papillary structure may lead to its misdiagnosis as a serous carcinoma or endometrioid carcinoma, and a clinical diagnosis of ovarian cancer or peritoneal carcinoma. Patient age, tumor-development pattern, and the clinical picture should be considered in differentiating between ependymoma and common ovarian or peritoneal cancer. The fact that ependymomas may originate from the ovary or peritoneum suggest that they may develop by the following means: (1) as an ectodermal ingredient of teratoma; (2) by neometaplasia of a tissue derived from the peritoneum and Mueller duct; and (3) from ectopic nervous system and fetal components (derived from primordial germ cells) remaining in the pelvis. Ependymoma of the central nervous system show infrequent ER and PgR expression, whereas ependymomas that develop from the ovary or peritoneum are highly positive for ER and/or PgR [6]. ER and PgR expression may thus differ according to the origin of the tumor cells from central nervous tissue or not [7]. A previous case report described a patient with an ER- and PgR-positive ovarian ependymoma who achieved stable disease after postoperative treatment with an aromatase inhibitor [8]. However, it is currently uncertain if hormone sensitivity is associated with a specific regimen, and if adnexectomy leads to improved survival.

Because ectopic ependymoma is very rare, it is difficult to establish this diagnosis before surgery. In the 17 previous cases reported in Japan, we were able to access the data for 11 cases, among which malignancy was confirmed preoperatively in nine, and ovarian cancer was suspected in eight cases [9–11]. Seven of the 11 patients were in their 20 s. A previous report suggested that strong chemotherapy may be administered unnecessarily when serous or endometrioid carcinoma is diagnosed pathologically [12].

In conclusion, although ectopic ependymoma is rare, it is important to consider it as a possible diagnosis in young women with suspected ovarian or peritoneal cancer. Further cases are needed to establish the clinical characteristics and optimal treatment strategies for this condition.

Conflict of interest

The authors declare that they have no conflict of interest.

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