Nov 1, 2004 - A case of primary ameloblastoma of the right sinonasal tract in a 66-year-old man is reported. The tumour presented as a radiographically solid ...
Copyright C APMIS 2005
APMIS 113: 148–50, 2005 Printed in Denmark . All rights reserved
ISSN 0903-4641
Primary sinonasal ameloblastoma Case report ˜ O,1 LEIRE ETXEGARAI,1 MARI´A CORRAL,2 JOSE´ M. BASURKO,3 COSME EREN ´ PEZ1 FRANCISCO J. BILBAO1 and JOSE´ I. LO Departments of 1Anatomic Pathology, 2Otolaryngology and 3Radiology, Hospital de Basurto, Basque Country University (UPV/EHU), Bilbao, Spain
Eren˜o C, Etxegarai L, Corral M, Basurko JM, Bilbao FJ, Lo´pez JI. Primary sinonasal ameloblastoma. APMIS 2005;113:148–50. A case of primary ameloblastoma of the right sinonasal tract in a 66-year-old man is reported. The tumour presented as a radiographically solid mass filling the right nasal cavity and sinuses and without continuity with maxillary alveola. After radical surgery plus postoperative radiotherapy, the patient has pursued a non-aggressive clinical course after nine months of follow-up. The paper reviews the clinico-pathological features of this rare tumour and supports the theory of its sinonasal epithelium origin. Key words: Ameloblastoma; sinonasal tract; immunohistochemistry; differential diagnosis. Dr. Cosme Eren˜o, Department of Anatomic Pathology, Hospital de Basurto, Avda. de Montevideo 18, 48013 Bilbao, Spain. cereno/hbas.osakidetza.net
Ameloblastomas are locally aggressive tumours with high risk of recurrence, that originate in the mandible and maxilla from odontogenic epithelial rests. Roughly 20% of ameloblastomas appear as growing masses in the maxilla, and 2% of them arise in the premolar region (1). The overwhelming majority of cases affecting the sinonasal cavity are tumours that grow in the maxilla and secondarily extend through the nasal and paranasal cavities (2). There are only a few genuine primary sinonasal ameloblastomas (SNAs) reported without connection with gnatic areas (3–7). The largest series belongs to the AFIP files with 24 cases collected during a 40-year period (1956–1996) (7). We report a new case of plexiform ameloblastoma that affects the right nasal cavity, ethmoidal and maxillary sinuses in a 66-year-old man. We review the literature about this rare Received 30 July 2004. Accepted 1 November 2004.
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tumour and focus mainly on the differential diagnosis and on the proposed histogenetic theories.
CASE REPORT Clinical Data A 66-year-old man consulted the otolaryngologist because of nasal obstruction and bleeding during the last few months. A CT scan showed a dense and opaque mass located in the right nasosinusal region, affecting the nasal cavity and maxillary and ethmoidal sinuses (Fig. 1), and eroding the malar bone and the orbit. There was no relationship with maxillary alveola. A radical right maxillectomy with sentinel node study and subsequent radiotherapy was performed. The patient is well and free of disease 9 months after surgery. Pathological Findings Multiple and irregular tissue fragments containing polypoid greyish areas and bony spicula, measuring 7¿4¿5 cm altogether, were fixed in formalin and
PRIMARY SINONASAL AMELOBLASTOMA
Fig. 2. Panoramic view of a neoplasm displaying a plexiform pattern of growth hanging from the right maxillary sinus surface epithelium (hematoxilin & eosin, ¿10).
Fig.1. Upper: Coronal CT image showing extensive replacement of the nasosinusal cavities and the integrity of the alveolar area. Lower: Macroscopic view of the surgical specimen with a tumour mass partially filling the sinuses and sparing the hard palate. submitted to the Laboratory of Anatomic Pathology. Additionally, the maxillectomy specimen measured 6.5¿3.5¿3 cm and showed a tumour mass of similar characteristics to the one described above growing in the nasal wall (Fig. 1). Serial cut sections of the maxillectomy specimen did not reveal tumour mass in continuity with maxillary alveola. Microscopically, the neoplasm was composed of a complex network of anastomosing epithelial cords within a hyaline fibrous stroma and arising from the surface epithelium of the maxillary sinus (Fig. 2). A thorough study of bone slices revealed focal pushing cortical erosion and integrity of maxillary alveola. Proliferating epithelial cords and nests contained a loose proliferation of stellated cells and showed a striking palisading arrangement in the peripheral rim (Fig. 3). The cells showed hyperchromatic and elongated nuclei and subnuclear vacuolization (reverse polarization). Mitoses were scarce. Cysts and squamous differentiation were not seen along the neoplasm, but basaloid areas were present. Lymph node metastases were not evidenced, but surgical margins were focally affected. The immunohistochemical profile of cytokeratins revealed striking positivity with keratin 19 in prolif-
Fig. 3. Histological detail of some typical tumour nests showing prominent peripheral palisading with inverse polarization (inset) and stellated central cells in a loose arrangement (hematoxilin & eosin, ¿250). erating cells. Additionally, stellated cells in the centre of cords were positive with keratin 13. Conversely, keratins 7 and 8 were negative.
DISCUSSION SNAs are exceedingly rare tumours, the histogenesis of which remains unclear. The most plausible theory is that they originate in presumed odontogenic remnants located in the sinonasal mucosa, but nothing has been demonstrated so far. To date, the largest published series of SNAs compiles only 24 cases during a 40-year period (7). Additionally, a handful of 149
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single cases have been reported in the international literature (3–6). Contrary to most gnatic ameloblastomas, which appear in patients 35 to 45 years old (1), the majority of SNAs arise in older people, particularly around the sixth decade of life (mean 59.8 years) (6, 7). The AFIP series (7) also shows that these tumours may affect either the nasal fossa (9/24) or paranasal sinuses (6/24) indistinctly, or both anatomic sites at the same time (9/24)(7). SNAs present a typical histology, with most cases showing a predominant plexiform growth pattern (6, 7). As in the case reported in this paper, a tumour origin from the metaplastic or native surface epithelium of the sinonasal tract can be microscopically demonstrated in a few other cases, thus supporting the primary sinonasal derivation of at least some SNAs (7). In this sense, the peculiar immunoprofile for keratins, with positive staining with keratin 13 only in stellated central cells, together with a strong and diffuse positivity with keratin 19, indicates its ameloblastic origin (8, 9). The differential diagnosis may remain a challenge in small biopsies if tissue fragments obtained for diagnosis are superficial and the typical histology of the tumour is not well represented in them. For instance, basaloid neoplasms may be a possible diagnosis if only basaloid areas are sampled. However, typically basaloid nuclear features and dense eosinophilic stroma are never present in SNAs. When affecting upper sinuses or nasal fossa, craniopharyngiomas may also be considered as a possible diagnosis. In this case, radiological and clinical manifestations, together with a different immunohistochemical profile (10), may be of help. Finally, some squamous cell carcinomas that arise in the upper aerodigestive tract may eventually display acantolysis and peripheral nest palisading, thus mimicking the characteristic arrangement of SNAs. However, a detailed view of the tumour nests will show the absence of both the reverse polarization of peripheral cells and the band-like dense subepithelial collagen deposition (11). The preferred treatment of SNAs is radical surgery, with or without radiotherapy to prevent recurrences. To the best of our knowledge, there are no reported cases with distant metastases or deaths caused by the tumour. To summarize, primary SNAs are very rare 150
neoplasms with a distinct immunohistochemical profile that must be distinguished from gnatic ameloblastomas, mainly on the basis of radiological and histological findings. Although very few cases have been reported so far, the largest published series of this tumour indicates that it usually pursues a benign clinical course after surgery.
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