PMC9083751_01
A - Mammography showing an ill-defined right breast sub-aerolar mass with eccentric lucent areas (craniocaudal view); B - Gross examination revealed a grey white tumor with multiple variably sized cysts containing friable mucoid material.
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Mammography revealed an ill-defined mass with irregular contours and eccentric lucent areas, as well as soft tissue swelling in the upper and central subareolar regions around the nipple (Figure 1A).
Photomicrographs of the tumor. A - Variable sized cysts filled with thyroid colloid like eosinophilic secretions (H&E; x200); B - Cysts lined by micropapillary fronds with high nuclear grade (H&E; x200); C - Invasive component composed of nests of tumor cells invading stroma (H&E; x400); D - Secretory material is positive for PAS (PAS; x200).
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Upon serial slicing the tumor, variably-sized cysts ranging from 1 to 2.5 cm were identified, containing thick gelatinous secretions (Figure 2A). Microscopy revealed variably sized cysts lined by flattened cuboidal epithelium to tall micropapillary fronds in some areas, with moderate nuclear grade (Figure 2B). An invasive focus consisting of nests of irregular tumor cells, infiltrating the cyst wall was identified (Figure 2C). The secretion was positive for Periodic acid Schiff (PAS) (Figure 2D).
Photomicrographs of the tumor. A - Membranous positive for HER2/neu (in tumor cells (x400) ASCO/CAP guidelines IHC score 3+; B - Positive Ki 67 expression in tumor cells (x400).
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The tumor was estrogen receptor (ER), progesterone receptor (PR) negative, and HER2/neu positive (ASCO/CAP guidelines IHC score 3+), (Figure 3A), with a Ki-67 index of 40-45% (Figure 3B).