2 Department of Radiology, Faculty of Medicine, Kyushu University, Fukuoka, Japan .... of Neuroscience, University of Florida, for reviewing our manu- script.
Neuro-radiology
Neuroradiology (1993) 35:462-465
Head and Neck Radiology
9 Springer-Veflag 1993
Intracranial adenoid cystic carcinoma mimicking meningioma: report of two cases 1".Morioka 1, I". Matsushima 1, K. Ikezaki 1, S. Nagata 1, M. Ohta 1, K. Hasuo 2, M. Fukui 1 l Department of Neurosurgery, Neurological Institute, Kyushu University, Fukuoka, Japan 2 Department of Radiology, Faculty of Medicine, Kyushu University, Fukuoka, Japan Received: 10 September 1992
Abstract. Two cases of intracranial a d e n o i d cystic carcinoma mimicking m e n i n g i o m a are reported. In one, M R I showed not only a h o m o g e n e o u s l y enhancing extra-axial t u m o u r attached to the dura m a t e r of the posterior cranial fossa, but also surrounding dural e n h a n c e m e n t , the "dural tail sign". In the second, C T d e m o n s t r a t e d a well-demarcated enhancing extra-axial turnout, indistinguishable from a sphenoid ridge m e n i n g i o m a extending into the orbit. T h e neuroradiological features of intracranial adenoid cystic carcinoma m a y thus closely resemble those of meningioma.
Key words: A d e n o i d cystic carcinoma - M e n i n g i o m a D u r a l tail sign
A d e n o i d cystic carcinomas, also k n o w n as cylindromas, arise f r o m the m a j o r salivary glands, the m i n o r salivary glands of the oral cavity, and the m u c o u s glands of the upper respiratory tract [1-4]. T h e y m a y also arise f r o m the lacrimal glands [2, 4] and occasionally f r o m the c e r u m e n glands of the external auditory canal [5]. Intracranial inv o l v e m e n t is rare, and n e u r o s u r g e o n s rarely have occasion to treat these t u m o u r s [6]. We recently e x a m i n e d two patients with a d e n o i d cyctic carcinomas w h o subsequently u n d e r w e n t intracranial operations with a p r e o p e r a t i v e diagnosis of meningioma.
Case reports Case 1
A 65-year-old man complained of headache, progressive over 2 years. A month before admission, he developed unsteadiness of gait and a floating sensation. Examination on admission revealed
Correspondence to: T. Morioka, Department of Neurosurgery, Neurological Institute Faculty of Medicine, Kyushu University 60, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812, Japan
mild truncal ataxia; the patient also had left conductive deafness due to chronic otitis media. CT showed a slightly hyperdense, well-marginated solid mass on the left of the posterior cranial fossa, with remarkable homogeneous enhancement after intravenous contrast medium (Fig. 1 a). MRI showed it to be isointense with grey matter on Tl-weighted images and hyperintense on T2 weighting. The lesion was consistent with a meningioma, showing homogeneous enhancement with intravenous gadolinium diethylene triamine pentaacetic acid (Gd-DTPA). In addition, the dura mater adjacent to the tumour enhanced extensively showing the "dural tail sign" (Fig. i b). With a presumptive diagnosis of meuingioma, a left suboccipital craniectomy was performed. The round, lobulated tumour spread widely along the dura mater around the sigmoid sinus. The initial impression was that of a meningioma. The main mass, clearly demarcated from the cerebellar hemisphere, was easily removed. However, the surrounding dura mater was thick and soft, and part of it was removed for histological examination. Since the patient was elderly, the dura mater, widely involved by the tumour, was left behind. The histological diagnosis was adenoid cystic carcinoma (Fig.2a). The thick dural tail showed dense fibrous tissue infiltrated by tumour cells (Fig. 2 b). Postoperative radiation treatment (whole brain 42 Gy, local 60 Gy) resulted in shrinkage of the residual tumour. Bone scintigraphy with 99mTc-HMDP and tumour scintigraphy with 67Ga citrate, performed postoperatively, failed to reveal a primary lesion. Three years after surgery, the patient is still alive with no neurological deficit.
Case 2
A 61-year-old man felt some tension in the left eye and noticed a tender nodule under the outer canthus 6 months before admission. Left proptosis gradually became evident, and he progressively lost left visual acuity. On admission, neurological findings included decreased left visual acuity, left papilloedema with retinal haemorrhage, left exophthalmos, limitation of ocular movements in all directions, left ptosis, and diminished corneal reflex and pupillary reaction to light on the left. CT disclosed a large mass extending both intraorbitally and intracranially (Fig. 3 a). External carotid angiography showed at to be hypervascular (Fig. 3 b). Preoperative diagnosis was a sphenoid ridge meningioma extending into the orbit. Through a left fronto-temporal craniotomy, the majority of the intraorbital and intracranial portions of the tumour was removed. Since it invaded the orbital muscles and the anterior part of the cavernous sinus, total removal was impossible.
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Fig. 1. a Coronal CT showing a solid enhancing mass on the left of the posterior cranial fossa, with surrounding oedema b Axial contrast-enhanced Tl-weighted MRI demonstrating a high signal, extra-axial lobulated mass; a dural "tail" (arrows) is seen along the petrous bone Fig. 2. a Photomicrograph showing typical cribriform tumour ceil arrangement. Haematoxylin and eosin (MS:E), • 27O b A portion of the dural "tail" showing dense fibrous tissue, infiltrated by tumour cells. H&E, • 270
Fig. 3. a CT showing a homogeneously enhancing tumour extending both intraorbitally and intracranially b External carotid angiogram showing a vascular mass arising from the sphenoid ridge
The tumour was histologically identified as an adenoid cystic carcinoma (Fig.4), probably originating from the lacrimal gland. No other tumour was found in any part of the body. Five months after surgery, recurrent tumour was found in the left orbit, the left middle fossa and in the ethmoid sinuses on both sides. The patient underwent left enucleation followed by partial removal of the recurrent tumour through anterior and lateral orbital approaches. In spite of radiation (50 Gy) and immunotherapy, the patient died of multiple systemic metastases 18 months after the first operation.
Discussion M o s t r e p o r t e d i n t r a c r a n i a l a d e n o i d cystic c a r c i n o m a s w e r e l o c a t e d at t h e b a s e of t h e skull, h a v i n g e x t e n d e d int r a c r a n i a l l y d i r e c t l y o r p e r i n e u r a l l y f r o m p r i m a r y lesions in n e i g h b o u r i n g structures, such as t h e l a c r i m a l gland, saliv a r y g l a n d , p a r a n a s a l sinus, or n a s o p h a r y n x [2, 6-8]. T h e f r e q u e n c y o f i n t r a c r a n i a l i n v a s i o n is r e p o r t e d as 4 - 2 2 % [1, 3, 9, 10]. Gonzfilez and Zttlch [11] r e p o r t e d i n t r a c r a n i a l
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Fig. 4. Photomicrograph showing tumour cells arranged in a cribriform pattern among the fibrous tissue. H&E, x 81
adenoid cystic carcinomas in the chiasmal and Gasserian ganglion regions. They suggested that the tumours in the chiasmal region originate from the nasal fossae or paranasal sinuses and invade the skull via the cribriform plate, whereas those in the Gasserian ganglion region arise from the glandular epithelia of the Eustachian tube. However, microscopically, the tumours usually infiltrated the perineural and perivascular spaces [3, 12, 13]. Therefore, spread along the nerve sheath and/or haematogeneous intracranial metastasis must be considered [7, 14]. Orbital adenoid cystic carcinoma is well known, with 166 cases in the literature up to 1986 [9]. They usually originate from the lacrimal gland and lie laterally in the orbit [2,15]. The tumour in case 2 probably arose in the lacrimal gland and extended intracranially, which resulted in a distribution very similar to that of a sphenoid ridge meningioma with intraorbital extension. The origin of the tumour in case 1 is unknown, but is thought to be from the Eustachian tube or mastoid air cells. CT findings in intracranial adenoid cystic carcinomas have been described in only a few cases [6, 7, 14]. Most were well-demarcated, hyperdense, extra-axial masses which usually enhanced homogeneously with contrast medium. There are no findings specific for adenoid cystic carcinoma and it has previously been noted that they are indistinguishable from those of meningioma [7]. The CT findings in our cases were also similar to those of meningiomas, and in case 2 angiography also demonstrated a hypervascular mass supplied by the external carotid arteries, resembling a meningioma. To our knowledge, there are no reports of MRI findings. In our case the tumour was isointense with grey matter on Tl-weighted images and hyperintense on T2 weighting, enhancing homogeneously with Gd-DTPA. Linear meningeal thickening and enhancement adjacent to the peripherally-located mass appeared to represent a dural "tail", very similar to that seen in meningiomas. Reports on the significance of the "dural tail sign" on contrast-enhanced MRI are conflicting. It was thought at
first to be highly specific for meningioma [16, 17]. Recently, however, a number of other causes have been described [18-20], as in our case 1. It is not clear whether the "tail" represents meningioma cell infiltration or reactive changes to the presence of the meningioma [16, 17]. Tokumaru et al. [16] suggested that the "tail" did not necessarily represent neoplastic invasion; however, localized nests of meningioma cells have been identified in the dura mater adjacent to meningiomas, in the area corresponding to the dural enhancement [17, 21]. In our case the "tail" was confirmed to represent extensive invasion of the dura mater by adenoid cystic carcinoma. Although there are noteworthy radiological similarities between adenoid cystic carcinoma and meningioma, the postoperative course of these turnouts is very different. The typical biological behaviour of adenoid cystic carcinoma is slow, aggressive, local growth leading to eventual death from local disease and/or metastases [1, 3, 6, 12, 13]. When adenoid cystic carcinoma appears at all possible during surgery, an effort should be made to remove all the tumour, including the invaded dura mater, as completely as possible. Once the histological diagnosis of adenoid cystic carcinoma is obtained, chemo- and/or radiotherapy should be added [6, 12]; this tumour is radiosensitive, but not radiocurable [6, 10, 12, 22]. In our case 1, postoperative radiotherapy was administered, and the turnout shrank substantially; symptomatic relief was also obtained. The tumour in case 2 recurred and metastasized systemically, in spite of radio- and immunotherapy; response of adenoid cystic carcinoma to radiation therapy may vary.
Acknowledgement. We thank Dr. A.N.Kalehua, Department of Neuroscience, University of Florida, for reviewing our manuscript.
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