British Journal of Radiology (2006) 79, 445-447
© 2006 British Institute of Radiology
doi: 10.1259/bjr/61959899
Primary subcutaneous sacrococcygeal ependymoma: a case report and review of the literature
Y T Ma, MRCP
P Ramachandra, FRCR
and
D Spooner, FRCR
The Cancer Centre, Queen Elizabeth Hospital, Edgbaston, Birmingham B15 2TH, UK
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Abstract
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Extraspinal ependymomas are rare. The majority occur in the sacrococcygeal region. The subcutaneous variety accounts for approximately two thirds of cases, which are commonly misdiagnosed as a pilonidal cyst or sinus. Treatment is complete surgical resection. The role of coccygectomy is controversial. Adjuvant radiotherapy is of benefit to those with an incompletely excised tumour. Up to 20% metastasise, chiefly to the inguinal lymph glands, but pulmonary metastases are also reported. Palliative chemotherapy has not been shown to be of any benefit. Long term follow-up is important as metastases can occur up to 20 years after initial presentation. We report a 37-year-old woman with a subcutaneous sacrococcygeal ependymoma with iliac lymph nodal metastasis at presentation.
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Introduction
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The ependymal cells form an epithelial sheet and line the ventricles in the brain and the central canal of the spinal cord. Ependymomas are tumours derived from ependymal cells and are usually confined to the central nervous system, occurring predominantly in children and young adults. They account for only 6% of intracranial gliomas, but in the spinal cord they are the most common tumours of glial origin, accounting for over 60%, mostly in the region of the cauda equina and the filum terminale [1].
Rarely, ependymomas occur outside of the central nervous system [1]. The majority occur in the sacrococcygeal subcutaneous tissue or the presacral regions [2–10]. We present a case of an ependymoma arising from the sacrococcygeal subcutaneous tissue with iliac lymph nodal metastasis at presentation.
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Case report
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A 37-year-old Caucasian lady presented with a 6-month history of an enlarging nodule at the base of her coccyx. She had always been aware of the presence of a small nodule but had thought this was "normal" for her. During the 6-month period the nodule had increased in size from less than 0.5 cm to over 3 cm in diameter. There was no history of urinary or faecal problems. She was seen at her local hospital and a diagnosis of a pilonidal sinus was made which was subsequently excised. Histological examination revealed this to be a subcutaneous myxopapillary sacrococcygeal ependymoma and she was referred to the regional centre for musculoskeletal oncology.
The full blood count, biochemical profile and tumour markers (alpha-fetoprotein (AFP), ß-human chorionic gonadotrophin (HCG), carcinoembryonic antigen (CEA) and CA-125) were normal. MRI of the abdomen and pelvis demonstrated a residual lobulated soft tissue mass, about 3 cm in diameter, lying anterior and to the right of the tip of the coccyx. A second smaller lesion was also visible between the right internal and external iliac arteries (Figure 1
). CT scanning of the thorax and abdomen demonstrated multiple liver cysts, but no evidence of lung or liver metastases. Isotope bone scanning revealed no evidence of skeletal metastases.
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Figure 1. MRI abdomen and pelvis. SagittalT2 short tau inversion recovery (STIR) sequence showing a 3 cm lobulated soft tissue mass lying anterior to the tip of the coccyx, and a second small rounded soft tissue mass superiorly in the pelvis.
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The residual mass was completely excised. Intraoperatively, it was seen near the tip of the coccyx but separate from it. Additionally, a 1 cm solid lesion with cystic elements was found above the right common iliac artery. This was thought to be a right iliac lymph node and was also completely removed. The histology of the specimens again confirmed a myxopapillary ependymoma (Figure 2). The majority of the tumour cells were positive for glial fibrillary acidic protein (GFAP) and S-100, but epithelial and other neural and neuroendocrine markers were negative. The resection margins were free of tumour cells and the smaller lesion was confirmed to be a nodal metastasis.
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Figure 2. Histology of the excised mass showing plump bipolar spindle cells and epithelial-looking cells arranged in loose fascicles with extensive myxoid degeneration forming pseudoacinar structures.
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She made a good post-operative recovery. No adjuvant therapy was offered, as there was no evidence of either macroscopic or microscopic disease. Re-staging CT scanning of the thorax, abdomen and pelvis at 3 months showed no residual or metastatic disease.
6 months following surgery she developed persistent right iliac fossa pain. CT scanning of the abdomen and pelvis now demonstrated a soft tissue mass 4.5 cm x 4 cm x 3.5 cm in the right pelvis and also the presence of an enlarged right internal iliac lymph node (1.5 cm), suggestive of recurrent disease. The right pelvic mass and iliac lymph node were completely excised. Histological examination of the pelvic mass revealed reactive tissue only. Histological examination of the right iliac lymph node confirmed metastatic myxopapillary ependymoma. Surgery was followed with adjuvant radiotherapy to the right pelvis (45 G in 25 daily fractions over 5 weeks). She has made a good recovery and is now being closely followed up in clinic.
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Discussion
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Primary extraspinal ependymomas are rare and usually occur in the subcutaneous sacrococcygeal or presacral regions. Mallory reported the first case in 1902 [5]. Since then there have been approximately 75 reported cases of extraspinal ependymomas, with the subcutaneous variety accounting for about 50 cases (Table 1) [2–10]. Most of the published cases of sacrococcygeal ependymomas have occurred in children and young adults, although there have been reported cases ranging from 2 months to 67 years of age [2–10]. The male to female ratio of affected individuals is roughly equal [2, 6].
Subcutaneous sacrococcygeal ependymomas are thought to arise from the coccygeal medullary vestige, an ependymal lined cavity forming the remnant of the caudal portion of the neural tube [11]. This theory is supported by Bale who found post-coccygeal ependymal vestiges in 10 of 15 random necropsies in infants [12]. Presacral ependymomas are thought to arise either from the extradural remnants of the filum terminale or as an extension from the intradural filum terminale [2, 3]. The frequent finding of sacral bone destruction and sacral nerve dysfunction in patients with presacral ependymomas supports this theory [4]. A germ cell origin has also been proposed which may explain the rare occurrence of ependymomas in the ovary and the mediastinum [2].
Most subcutaneous sacrococcygeal ependymomas are of the myxopapillary variety [7]. The other histological types, according to the World Health Organization (WHO) classification, are papillary and subependymal [2]. Characteristically, subcutaneous sacrococcygeal ependymomas grow slowly and often reach a relatively large size prior to presentation. The majority of patients are asymptomatic. Consequently, these tumours are frequently misdiagnosed clinically as a pilonidal cyst or sinus [6, 8]. This was a feature in our case.
Ependymomas confined to the central nervous system rarely metastasise outside of the cerebrospinal fluid (CSF) pathway. Conversely, up to 20% of subcutaneous sacrococcygeal ependymomas have been reported to develop distant metastases [2, 6, 8]. This has often been attributed to the easier access of these tumours to lymphatic and vascular vessels. Pulmonary, pleural, osseous, inguinal nodal and subcutaneous metastases have been documented [2–10]. Our patient was found to have a synchronous right iliac lymph nodal metastasis, which is an unusual finding. Currently, no reliable clinical or histological feature exists to help predict the development of metastases. Distant metastases can occur 10–20 years after initial presentation [6]. Consequently, patients need to be under regular follow-up for many years.
Immunohistochemical staining helps to make the diagnosis. Typically, there are positive reactions to glial fibrillary acidic protein (GFAP), S-100 and vimentin [2]. This was seen in our case; the tissue reacted positively to GFAP and S-100.
The treatment of subcutaneous sacrococcygeal ependymomas remains controversial because of their rarity. The favoured treatment is surgical excision. Complete excision appears to be essential to prevent local recurrence. Surgical removal of the coccyx may also be required if the tumour is attached to this bone [2]. Some authors have suggested routine coccygectomy as part of the primary surgical treatment, because of an apparent reduction in the recurrence rate. Aktu
et al carried out a review of all reported cases of sacrococcygeal extraspinal ependymomas [9]. They found that local recurrence did not occur if the coccyx was removed (four patients, mean follow-up period of 3 years). Conversely, if the coccyx was not excised, local recurrence occurred in 71% of patients (5 out of 7 patients). It appears that the likely benefit for coccygectomy is in the group of patients with presacral ependymomas, with involvement of the coccyx. In our case, as the mass was found separate to the coccyx, coccygectomy was therefore not performed.
Lymphadenectomy is also recommended in patients who present concurrently with inguinal lymph nodal metastases [8]. The role of lymphadenectomy in patients with iliac lymph nodal metastases is unknown as it is very rare. Although our patient had complete excision of the ependymoma and removal of the affected iliac lymph node, she developed local recurrence within 6 months of surgery suggesting a possible role for regional lymph node dissection.
Intracranial ependymomas are radiosensitive; radiotherapy is an important local therapy [8]. However, radiotherapy has not been found useful as primary treatment for subcutaneous sacrococcygeal ependymomas. In those with incompletely excised tumour or in the presence of metastases, adjuvant radiotherapy is recommended [2, 8]. There is no evidence that these tumours respond to chemotherapy [2, 8].
Although extremely rare, it is important to consider subcutaneous sacrococcygeal ependymomas in the differential diagnosis of a sacrococcygeal mass. In the absence of metastatic disease, complete excision of the tumour with regional lymph node dissection will usually result in a prolonged disease-free survival. Once metastases develop, the disease tends to be slowly, but unremittingly, progressive.
Received for publication May 5, 2004.
Revision received May 13, 2005.
Accepted for publication May 19, 2005.
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References
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Abstract
Introduction
