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Figure 3. Borderline/ atypical proliferative/ low malignant potential mucinous tumor, gastrointestinal type with microinvasion. Intermediate-power magnification (3A): The microinvasive area illustrated here shows complex anastamosing epithelium, irregular nests with a haphazard arrangement within stroma and focal cleft-like spaces around nests, and an associated stromal reaction. Other areas of the tumor showed classic features of mucinous borderline tumor, gastrointestinal-type (not shown). 3B: High-power magnification of a different case showing nests surrounded by clear spaces. The cells have atypical nuclei and abundant, partially mucinous cytoplasm. Submitted by Russell Vang, MD