Respiratory epithelial adenomatoid hamartoma of the anterior nasal septum a rare localisation of an unusual tumour in a child: a case report
© licensee BioMed Central Ltd. 2009
Received: 9 June 2009
Accepted: 25 August 2009
Published: 16 September 2009
Hamartomas are non-neoplastic lesions constituted by a mixture of tissues indigenous to the region. Respiratory epithelial adenomatoid hamartomas are characterised by glandular proliferation lined by ciliated airway epithelium. Their localisation in the nasal cavity is rare and most frequent cases described so far were associated with the posterior nasal septum.
A 9-year-old Caucasian boy presented with long-standing nasal obstruction. A large right nasal mass was evident on physical and CT examinations. It was surgically removed from the anterior nasal septum under general anaesthesia. Histologically, the diagnosis of REAH was established. The tumour lined by stratified squamous and ciliated respiratory epithelium was characterised by prominent glandular proliferation. By immunohistochemistry, the tumour was positive for cytokeratins, smooth muscle actin, vimentin, laminin, collagen type IV, CD8, and CD68. No S-100 immunoreactivity was observed. The patient has been asymptomatic for 12 months with completely healed lining of the nose.
Respiratory epithelial adenomatoid hamartoma, although rare, must be taken into consideration in differential diagnosis of nasal exophytic lesions.
Glandular lesions of the sinonasal tract are uncommon and may cause a diagnostic dilemma. If common salivary gland tumours are excluded, most of the other glandular lesions include respiratory epithelial adenomatoid hamartomas (REAHs), inverted schneiderian papillomas and sinonasal adenocarcinomas (SNACs) of the intestinal (ITAC) and nonintestinal (non-ITAC) types . Hamartomas are benign, non-neoplastic lesions constituted by a mixture of tissues which are indigenous to the region. They result from inborn errors of tissue development . REAHs are characterised by glandular proliferation lined by ciliated epithelium originating from the airway epithelium . Their localisation in the nasal cavity is unusual [3, 4], with more common occurrence in males . Association with nasal polyps supports the hypothesis that inflammation could be one of the inducing factors . In the nasal cavity, REAHs are mostly associated with the posterior nasal septum , although lesion arising from the lateral nasal wall has also been reported . The involvement of the maxillary sinus is extremely rare , although occasional occurrence of REAHs in areas surrounding nasal cavity, such as the ethmoid sinus, frontal sinus and nasopharynx has been described . Apart from REAHs, folliculo-sebaceous cystic hamartomas, localised in the skin of the vestibule or around the nose , and sinonasal fibro-osseous hamartomas, originating from the bones of the nose and paranasal sinuses  have been reported in the sinonasal tract. Complete surgical resection of a REAH is the treatment of choice .
The reported localisation of the tumour is unusual and REAHs have rarely been described in children [2, 3]. The awareness of possible occurrence of this lesion in the discussed site is important for differential diagnosis. Inverted schneiderian papilloma and adenocarcinoma should always be considered in the sinonasal tract [4, 6]. Despite characteristic histological features that distinguish these tumours, the differential diagnosis can be challenging in cases of small or fragmented endoscopic biopsies . Appreciable allelic loss within REAH, observed in previous studies, supports the hypothesis that the lesion might be a benign neoplasm rather than a developmental malformation .
Ki-67 staining has been found restricted to the basal/myoepithelial layer, demonstrating a low proliferation index . In our case there was also no visible mitotic activity. REAHs reported by Ozolek et al.  were positive for cytokeratin but negative for smooth muscle actin, S-100 protein, calponin, CK20, and CDX-2. They postulated that because of absence of myoepithelial markers, the cells surrounding secretory acini should be considered basal and not myoepithelial cells. In the lesion presented in this case, we observed myoepithelial cells expressing smooth muscle actin. Our REAH contained cells immunostained for vimentin in the stroma and also in the lining epithelia. Vimentin content is typical for connective tissue cells but it has also been found in normal respiratory epithelium . However, it seems most likely that occasional intraepithelial vimentin-positive cells observed in our tumour represented migratory cells. The tumour was accompanied by chronic inflammation, which is in accordance with previous reports . Positive reaction for CD8 disclosed numerous T lymphocytes, typically observed in chronic inflammation of the nasal mucosa . We have also found numerous CD68-immunoreactive macrophages, presumably belonging to the population of antigen presenting cells . Distribution of collagen type IV and laminin revealed by immunostaining in the tumour did not deviate from the pattern observed in normal nasal mucosa .
Respiratory epithelial adenomatoid hamartoma, although rare, must be taken into consideration in differential diagnosis of nasal exophytic lesions. Hamartoma of the anterior nasal septum can be effectively removed with indications and extent of the resection like in benign tumours.
CT: computed tomography; HE: hematoxylin and eosin; ITAC: intestinal type adenocarcinoma; non-ITAC: non-intestinal type adenocarcinoma; REAH: respiratory epithelial adenomatoid hamartomas; SNAC: sinonasal adenocarcinoma.
Written informed consent was obtained from the patient's parents for publication of this case report and accompanying images. A copy of the written consent is available from the journal's Editor-in-Chief.
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