Respiratory epithelial adenomatoid hamartoma

B.M. Wenig

Definition

Benign nonneoplastic overgrowth of indigenous glands of the nasal cavity, paranasal sinuses and nasopharynx associated with the surface epithelium, and devoid of ectodermal neuroectoder-mal, and/or mesodermal elements.

Synonyms

Glandular hamartoma; seromucinous hamartoma.

Epidemiology

Hamartomas of the sinonasal tract and nasopharynx are uncommon. The majority of them are of pure epithelial type (respiratory epithelial adenomatoid hamartoma) {2766}, although pure mesenchymal hamartomas or mixed epithelial-mesenchymal hamartomas may also rarely occur {14,106,933,2766}. Respiratory epithelial adenomatoid hamartomas predominantly occur in adult patients with a decided male predominance; patients range in age from the 3rd to 9th decades of life, with a median age in the 6th decade {2766}.

Etiology

Respiratory epithelial adenomatoid hamartomas often arise in the setting of inflammatory polyps, raising a possible developmental induction secondary to the inflammatory process {2766}.

Localization

The majority occur in the nasal cavity, in particular the posterior nasal septum; involvement of other intranasal sites occurs less often and may be identified along the lateral nasal wall, middle mea-tus and inferior turbinate {2766}. Other sites of involvement include the nasopharynx, ethmoid sinus, and frontal sinus. Most are unilateral, but some may be bilateral.

Clinical features

Patients present with nasal obstruction, nasal stuffiness, epistaxis and/or chronic (recurrent) rhinosinusitis. The symptoms may occur over months to years.

Associated complaints include allergies. Macroscopy

Lesions are typically polypoid or exophytic with a rubbery consistency, tan-white to red-brown appearance, measuring up to 6 cm in greatest dimension {933,2766}.

Histopathology

The lesions are dominated by a glandular proliferation composed of widely-spaced, small to medium-sized glands separated by stromal tissue. In areas, the glands arise in direct continuity with the surface epithelium, which invaginate downward into the submucosa. The glands are round to oval, and composed of multilayered ciliated respiratory epithelium often with admixed muco-cytes. Glands distended with mucus can be seen. A characteristic finding is stromal hyalinization with envelopment of glands by a thick, eosinophilic basement membrane. Atrophic glandular alterations may be present in which the glands are lined by a single layer of flattened to cuboidal epithelium. Small reactive seromucinous glands can be seen. The stroma is oedematous or fibrous, and contains a mixed chronic inflammatory cell infiltrate.

Additional findings may include inflammatory sinonasal polyps, hyperplasia and/or squamous metaplasia of the surface epithelium unrelated to the adeno-matoid proliferation, osseous metaplasia, rare association with inverted type Schneiderian papilloma, and rare association with a solitary fibrous tumour {2766}.

Prognosis and predictive factors

Conservative but complete surgical excision is curative.

Respiratory Epithelial

Fig. 1.33 Respiratory epithelial adenomatoid hamartoma (REAH). A The glandular proliferation arises in direct continuity with the surface epithelium with invagination downward into the submucosa. Clusters of seromucinous glands are seen (arrow). B Pseudostratified epithelium with cilia within the adenomatoid collections of a REAH hamartoma. C Cilia along the luminal border of the cells (arrows). D Atrophic changes in which the glands are lined by a single layer of flattened to cuboidal-appearing epithelium. Note the prominent thickened stromal hyalinization enveloping the glands.

Fig. 1.33 Respiratory epithelial adenomatoid hamartoma (REAH). A The glandular proliferation arises in direct continuity with the surface epithelium with invagination downward into the submucosa. Clusters of seromucinous glands are seen (arrow). B Pseudostratified epithelium with cilia within the adenomatoid collections of a REAH hamartoma. C Cilia along the luminal border of the cells (arrows). D Atrophic changes in which the glands are lined by a single layer of flattened to cuboidal-appearing epithelium. Note the prominent thickened stromal hyalinization enveloping the glands.

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