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Case report |
1 Sezione Scientifica di Diagnostica per immagini, Radioterapia e Medicina Nucleare, 2 Dipartimento di Chirurgia Generale ed Endoscopica and 3 Università degli Studi "Federico II" di Napoli, Dipartimento di Scienze Biomorfologiche e Funzionali, Istituto di Anatomia Patologica
Correspondence: Dr Salvatore Cappabianca, Viale Farnese, 36, 80131-Napoli, Italy
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Abstract |
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Introduction |
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Ependymomas outside the confines of the cranium and spinal cord are rare. Direct extension into the soft tissues of the sacrococcygeal area may occur from a primary ependymoma of the spinal cord, cauda equina or filum terminale [5]. Alternatively they may occur as a primary pre-sacral, pelvic or abdominal tumour, or as a primary tumour of the skin and subcutaneous tissue of the sacrococcygeal area without any demonstrable connection with the spinal cord [6–9].
On the other hand, extraspinal ependymomas present in two characteristic locations: in the soft tissue posterior to the sacrum or in the pelvis, and in the retro-rectal space anterior to the sacrum [6].
The Authors report a case of a myxopapillary ependymoma in the ischioanal fossa, demonstrated by MRI. To our knowledge, our case is the first lesion reported at this site.
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Case report |
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There were no abnormalities on neurological examination.
The patient underwent an MR examination with a 1.0 T superconductive scanner (Magnetom SP 42 E; Siemens, Erlangen, Germany); spin-echo T1 weighted images in all orthogonal planes (repetition time (TR)=450, echo time (TE)=10) before and after intravenous administration of gadolinium (0.1 mmol kg-1 of Gd-DTPA – Magnevist, Schering) and axial spin-echo DP-T2 weighted sequences (TR=2000, TE=13/80) were obtained. A soft-tissue mass located in the right ischioanal fossa, closely related to the anal canal wall, was demonstrated; it was sharply defined, of hypo-isointense signal intensity on T1 weighted images, and with inhomogeneous moderate increased signal on T2 weighted images (Figures 1 and 2
). After intravenous administration of gadolinium, the lesion showed highly inhomogeneous enhancement, characterized by a low signal intensity peripheral rim, with central focal nodules of marked enhancement. No enhancing strands extending across the mass were demonstrable (Figure 3). There were no other abnormalities.
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Surgical removal of the mass was performed; no connection was found between the mass and the filum terminale. Pathology with immunohistochemical staining revealed a papillary group of cubic to cylindrical cells immersed in a loose metachromatic myxoid stroma, with psammomatous calcifications. The neoplastic cells were arranged in papillary groups in an epithelial-like fashion with respect to some spindle cells in the core of the papillary group.
The diagnosis of myxopapillary ependymoma was made.
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Discussion |
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The appellation "myxopapillary" is based on the tendency of this ependymoma to produce mucin and form papillae by virtue of its arborizing vasculature, replacing the architecture of the normal filum terminale [9]. Myxopapillary ependymoma, a low grade glioma, is characterized by distinctively abundant supporting fibrous connective stroma, with foci of mucinous degeneration and mucin secretation by tumour cells [3, 4].
Ependymomas are rare outside the central nervous system and may be found in four general situations: metastatic extension from a primary central nervous system neoplasm; direct extension into the soft tissue of the sacrococcygeal area from primary ependymoma of the spinal cord, filum terminale or cauda equina [5]; primary tumour of the skin and subcutaneous tissue without any demonstrable connection with the spinal cord [2, 8, 9]; primary presacral, pelvic or abdominal tumour [6].
Our case fell into the latter category of primary pelvic myxopapillary ependymoma.
Ectopic ependymomas have also been reported in the mediastinum, uterosacral ligament, ovary and lung [11–14].
The origin of extraspinal ependymomas has been attributed to the coccygeal medullary vestige, an ependymal cell-lined cavity, that is a remnant of the caudal portion of the neural tube, which is located beneath the skin of the post-natal pit, over the tip of the coccyx [8, 15]. These vestiges are a common finding in infants and childhood (median age 17 years) and may evolve with malignant degeneration, but usually involute or regress [8, 16]. Nevertheless, ependymal cells may be found within the coccygeal ligament as well as in heterotopic positions, and it is therefore not surprising that ependymomas may rarely occur in extraspinal locations and particularly in the soft tissue posteriorly to the sacrum or in the pelvis in the retro-rectal space [6].
Myxopapillary ependymomas clinically appear to be slowly progressive tumours [3, 9, 16]. The clinical presentation depends on the location: patients, whose tumour is pelvic, present predominantly with a palpable mass at pelvic and/or rectal examination, often associated with bowel and bladder dysfunction and in many cases, with symptoms of sacral nerve root involvement, as loss of the ankle jerk and/or decreased rectal sphincter tone [6].
Prognosis appears not to be related to mitotic activity, cytological features, extensive mucinous change and hyalinization [3]. Systemic metastases of myxopapillary ependymomas, especially in extraspinal locations, have been documented [3, 5, 6, 16–18]. Helwig and Stern, in their series of 32 subcutaneous sacrococcygeal myxopapillary ependymomas, reported an incidence of 17%, the majority of which occurred in the lung and inguinal lymph nodes [6, 8, 16, 18, 19]. Other reported sites are the vertex of the skull and vertebral bodies [16, 20].
The imaging features of ependymoma developing outside the central nervous system have not been extensively reported; however, the features on CT and MRI are similar to those of ependymomas in the spinal canal [2, 21].
Contrast enhanced CT demonstrates a mass of soft tissue density which enhances after intravenous contrast administration [2]. T1 weighted on MRI sequences demonstrate low-intermediate homogeneous signal intensity within the mass; which post intravenous gadolinium administration, shows focal nodules of enhancement peripherally with strands of enhancement extending across the mass, or intense homogeneous enhancement. T2 weighted images on MRI show high signal, slightly lower than adipose tissue, within well circumscribed mass. The mass frequently has a peripheral rim of low signal due to the local deposition of hemosiderin. Focal necrosis, cystic degeneration and/or haemorrhage may result in an inhomogeneous lesion with mixed signal intensity [2, 21].
The differential diagnosis of a pelvic myxopapillary ependymoma includes inflammatory diseases (perirectal abscesses; internal fistulas), congenital tumours (chordomas; teratomas; dermoids), other neurogenic (neurofibroma) and osseous neoplasms or miscellaneous lesions as well as anterior meningoceles and metastatic tumours.
To our knowledge, this case is the first reported one of myxopapillary ependymoma of the ischioanal fossa in an adult patient.
Received for publication March 9, 2002. Revision received October 24, 2002. Accepted for publication January 10, 2003.
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