Heterotopic gastrointestinal mucosa in the oral cavity of adults Fabiana Martins, MDS, a Karen Renata Hiraki, PhD, b Maria Ângela Mimura, PhD, a Basílio de Almeida Milani, DDS, c Marina Gallottini, PhD, a Marília Trierveiler Martins, PhD, a and Suzana Orsini Machado de Sousa, PhD a University of São Paulo, São Paulo; and University of Uberlândia, Minas Gerais, Brazil Heterotopic gastrointestinal mucosa (HGM) is a rare entity observed in the head and neck region and occurs more frequently in male infants and children. The floor of the mouth and anterior aspects of the tongue are the most commonly affected sites. Histologically, HGM resembles gastric, intestinal or colonic mucosa with areas of squamous epithelium, which can be cystic or solid. In the current report, 2 cases of HGM affecting the oral mucosa in patients over 35 years of age are presented, and one of these cases presented 2 nodules in different locations. Both cases represented solid lesions instead of the more common cystic presentation showing gastric glandular-type tissue that was lined with pseudostratified columnar epithelium containing crypts and fundic glands. Immunohistochemical analysis revealed positive expression of cytokeratins 7, 8 and 18 and smooth muscle actin (SMA). In both cases, the final diagnosis was HGM, and conservative surgical excision was performed. (Oral Surg Oral Med Oral Pathol Oral Radiol 2013;115:e51-e54) Choristomas consist of histologically normal tissue situated in an abnormal location. 1 Heterotopic gastro- intestinal mucosa (HGM) is rarely observed in the head and neck region and occurs more frequently in male infants and children. The floor of the mouth and the anterior aspects of the tongue are the most commonly affected sites within the oral cavity, although HGM has been reported at other sites, such as the hypopharynx, anterior neck, larynx, submandibular gland and lip. 2-4 Histologically, HGM resembles gastric, intestinal or colonic mucosa that is lined by squamous, ciliated, or columnar epithelium, which can be cystic or solid. The cystic lesions are more frequently reported and have been termed heterotopic gastrointestinal cysts or duplication cysts. In both types of heterotopic mucosa, secretory glands composed of parietal and chief cells, crypts and bundles of smooth muscle can also be observed focally or even diffusely. 3,5 Although the pathobiology of HGM remains poorly characterized, some theories have been proposed to explain the presence of HGM in locations other than the gastro- intestinal tract, such as the oral cavity. The most widely accepted theory is that HGM is the result of the entrapment of islands of endodermal tissue that lined the primitive stomodeum during the fusion of embry- onic processes. 6 The clinical differential diagnosis for HGM is vari- able and usually depends on the age of the patient and the site of the lesion. Thus, dermoid and thyroglossal duct cysts, hemangiomas, lymphangiomas, lipomas, salivary gland neoplasms and diseases such as ranula may be included in the differential diagnosis. 3 Complete conservative surgical resection is the treat- ment of choice and generally prevents recurrences. 7 At present, fewer than 45 cases have been reported in the literature, and of these, approximately 33 were oral lesions. 4,5 Most patients are diagnosed during child- hood as a result of difficulties in feeding, swallowing, breathing, and speech. 7 Here, we present 2 cases of oral HGM diagnosed in patients over 35 years of age. Morphological and immunohistochemical aspects of these cases are discussed. CASE REPORT 1 A 58-year-old African Brazilian woman presented with 2 firm and painless nodules located on the mid portion of the tongue and the left side of the floor of the mouth (Figure 1A and B). According to the patient, she had similar lesions excised during childhood, but she was not aware of a previous diagnosis. Her major complaint was that of a poor fitting prosthesis. The lesion on the tongue was ulcerated and measured approximately 1.0 cm in diameter. The second lesion presented a red and white appearance and measured 2.0 cm in diameter. Incisional biopsies of both lesions were performed. With the diagnosis of gastrointestinal choristoma, both lesions were excised. Histological examination of both lesions showed mucosal tissue lined in part by stratified squamous epithelium and gastric-like epithelium, which exhibited One of these cases was presented recently (July 2012) at the IAOP. The abstract was published in Oral Surgery, Oral Medicine, Oral Pathology and Oral Radiology in October. a Department of Oral Pathology and Oral Diagnosis, School of Dentistry, University of São Paulo. b Department of Microbiology, University of Uberlândia. c Department of Oral Surgery, School of Dentistry, University of São Paulo. Received for publication Sep 2, 2012; returned for revision Dec 16, 2012; accepted for publication Dec 21, 2012. Ó 2013 Elsevier Inc. All rights reserved. 2212-4403/$ - see front matter http://dx.doi.org/10.1016/j.oooo.2012.12.010 e51 Vol. 115 No. 6 June 2013