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Figure 2. Borderline/ atypical proliferative/ low malignant potential mucinous tumor, gastrointestinal type with intraepithelial carcinoma (2A; high-power magnification): The columnar cells show an increased nuclear-to-cytoplasmic ratio with some degree of loss of cytoplasmic mucin. The nuclei are enlarged, round to oval, and show variation in size and shape. The nuclei contain prominent nucleoli and irregularly distributed chromatin. Severe nuclear atypia, shown here, is the criterion recommended by the workshop for a diagnosis of intraepithelial carcinoma, regardless of architecture. The problematic lesion in Fig. 2B (low-power magnification) is from another case and is subject to more than one interpretation. It shows a complex intracystic proliferation with labyrinthine epithelium that might be considered as intraepithelial carcinoma by some gynecologic pathologists; however, architectural complexity would not be considered by the workshop as sufficient for a diagnosis of intraepithelial carcinoma if the nuclear atypia is not severe (high-power magnification not shown). On the other hand, lesions within stroma (rather than intracystic) and having this degree of complexity may represent the confluent/expansile type of invasive mucinous carcinoma if the size measures greater than that allowed for microinvasion. Submitted by Russell Vang, MD