Squamous Morules (Microcarcinoids) in Gastroesophageal Polyps; a Mimicker of Invasive Carcinoma

Colorectal lesions termed squamous morules or microcarcinoids display predominantly squamous and variable endocrine differentiation and are often found in colorectal adenomas with high grade dysplasia thus mimicking invasion. Herein, we describe histopathologic, immunohistochemical classification and clinical correlation of analogous lesions in the esophagus and stomach. We identified five cases (3 men, 2 women) from November 2004-March 2013 of gastric and gastroesophageal polyps with squamous morules. Four of the patients were white. The median age was 70 years (range 59-85 years). Two patients presented with gastrointestinal bleeding, one was undergoing routine screening, and two were followed up for Barrett esophagus (BE) and a history of gastric polyps respectively. Three lesions were gastric, one gastroesophageal (GE), and one patient had both GE and proximal gastric lesions. Four patients had multiple polyps; one had a 2.5 cm polypoid GE lesion. The median size of the polyps was 1.5 cm. All of the gastric squamous morules arose in hyperplastic polyps (HP) (one patient had separate fundic gland polyps). Two HPs showed high grade dysplasia, 1 low grade dysplasia, and 1 erosions and reactive changes. One of the GE lesions was associated with polypoid papillary high grade dysplasia arising in BE, this patient had follow up biopsy 1 month later showing BE with features indefinite for dysplasia. He died in 2009 (5 years) of unknown cause. The remaining patients are alive. The areas of squamous morule formation ranged in size from 1-3 mm. They were multifocal showing a lobular growth pattern connecting directly to the epithelium. Four of the lesions demonstrated pseudolumina. Immunohistochemical analysis was done on all cases. Sixty percent showed nuclear beta catenin, and all demonstrated a low KI67 index (< 2%). Endocrine markers (synaptophysin, chromogranin) were expressed in all of the lesions, and P63 showed focal labeling in two lesions. In summary, the histopathological features and immunohistochemical labeling of GE squamous morules/ microcarcinoids are similar to those previously described in the colorectum. GE lesions can be associated with reactive processes and more frequently in a background of dysplasia. Underrecognition of upper gastrointestinal squamous morules provides potential for over diagnosis of invasive carcinoma. Familiarity with the histopathologic pattern and immunoprofile can aid in avoiding this pitfall.