Seromucinous hamartomas: a clinicopathological study of a sinonasal glandular lesion lacking myoepithelial cells

To describe seven cases of sinonasal seromucinous hamartoma. The clinicopathological and immunohistochemical features of seven seromucinous hamartomas were analysed. There were four men and three women. Six lesions involved the posterior nasal septum and one the lateral wall. Size ranged from 6 to 40 mm. Four patients had no recurrences. One patient had local recurrences 24 and 60 months after diagnosis. The masses were covered by respiratory epithelium. Their stroma was oedematous to fibrous and contained invaginated respiratory epithelium forming glands and cysts, cysts with cuboidal to flat epithelium, and small serous glands, ducts and tubules with lobular and irregular haphazard patterns. One case had numerous glands surrounded by hyalinized basement membrane with features of respiratory epithelial adenomatoid hamartoma (REAH). One case had focal REAH-like changes. Both respiratory and serous components were positive for cytokeratin (CK) 7 and CK19. The serous component lacked myoepithelial cells when stained for CK14, p63, calponin and muscle-specific antigen in five cases. Seromucinous hamartomas show a broader histopathological appearance than previously reported. The serous proliferation in these lesions lacks myoepithelial cells. The presence of occasional REAH-like features and common location in the posterior nasal septum suggest a spectrum from pure seromucinous hamartoma to REAH.