PMC5831977_01
Mammogram (right mediolateral oblique view) confirming a 25 mm, well-circumscribed nodule within the substance of the breast. This lesion had been previously documented and was slowly enlarging in size over several years.
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fig1
A differential diagnosis of sebaceous cyst versus another well-circumscribed lesion was given (Figure 1).
Histopathologic findings: (a) low magnification of skin surface showing intact, thinned epidermis with narrow grenz zone of uninvolved papillary dermis and subjacent epithelial proliferation of basaloid lesional cell nests arranged in a "jigsaw pattern," H&E stain, 40x; (b) low magnification of deep edge of tumor with basaloid nests pushing into subcutaneous adipose tissue, H&E stain, 40x.
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fig2
It was not encapsulated and showed a pushing border with some of the deeper nests of cells extending into the subcutaneous adipose tissue (Figure 2).
Histopathologic findings: (a) intermediate magnification of "jigsaw pattern" with biphasic cell nests showing outer somewhat palisaded small blue cells and central basaloid cells with slightly more abundant eosinophilic cytoplasm as well as fibrous stroma, H&E stain, 200x; (b) basement membrane material investing periphery of epithelial nests, PAS stain, 200x.
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fig3
Some tumor cell nests appeared to be comprised entirely of cells with a basaloid phenotype and a suggestion of peripheral palisading, while other nests appeared somewhat morphologically biphenotypic with slightly smaller and darker peripheral myoepithelial-like cells as well as a second population of central cells with more abundant and eosinophilic cytoplasm and a tendency toward spindling or whorling (Figure 3).
High magnification immunohistochemistry of selected cutaneous basaloid tumor markers: (a) focal membranous and cytoplasmic positivity in center of tumor cell nests with sparing of outer cells, CKAE1/3, 400x; (b) diffuse and strong cytoplasmic positivity in center of tumor cell nests with comparative sparing of myoepithelial-like edges, CK5/6, 400x; (c) patchy cytoplasmic and membranous positivity in center of tumor cell nests with sparing of outer cells, CK7, 400x; (d) diffuse and strong nuclear positivity throughout tumor cell nests, p63, 400x; (e) diffuse nuclear positivity of moderate to strong intensity throughout tumor cell nests, SOX10, 400x.
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fig4
The AE1/3 and CK7 patterns of immunoreactivity were similar with staining of the center of some basaloid tumor cell nests in a mixed membranous and cytoplasmic pattern of positivity (Figure 4). The tumor cells were also noted to show diffuse nuclear immunoreactivity with p63 and SOX10 (Figure 4).
High magnification immunohistochemistry of selected breast tumor markers: (a) diffuse nuclear and cytoplasmic positivity of moderate intensity, mammaglobin, 400x; (b) diffuse and strong nuclear and focal cytoplasmic positivity throughout tumor cell groups, GATA3, 400x; (c) diffuse and moderately intense cytoplasmic positivity throughout tumor cell groups, E-cadherin, 400x.
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fig5
In addition, mammaglobin, GATA3, and E-cadherin were found to be immunoreactive in the majority of tumor cells (Figure 5).