case_images: PMC9358339_01
case_images: (a) Mammography showed a tumor shadow with a clear boundary in the outer upper quadrant
  of the left breast. (b) Breast sonography showed a lobulated hypoechoic tumor with a
  rough boundary. (c) MRI showed a 29-mm neoplastic lesion in the outer upper quadrant of
  the left breast.
case_images: 10.1177_2050313X221116667-fig1.jpg
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case_images: fig1-2050313X221116667
case_images: Regarding imaging findings, mammography showed a tumor shadow with a clear boundary in outer upper quadrant of the left breast (Figure 1(a)); breast sonography showed a lobulated hypoechoic tumor with a rough boundary (Figure 1(b)); and magnetic resonance imaging showed a 29-mm neoplastic lesion in the outer upper quadrant of the left breast (Figure 1(c)).
case_images: A 43 mm x 41 mm x 33 mm gray tumor with a clear boundary could be seen in the outer
  upper quadrant of the gross specimen of total left mastectomy. Multi-nodule and
  lobulated structures could also be seen in this specimen.
case_images: 10.1177_2050313X221116667-fig2.jpg
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case_images: On the cut surface, a multi-nodule-to-lobular structure could be seen (Figure 2).
case_images: HE-stained images of the surgical specimen. (a) In the low-magnification field of view,
  a high cell density and diffuse proliferation were seen in the tumor. (b) In the
  medium-magnification field of view, the arrangement of tumor cells along the fibrous
  membrane was very obvious. (c) In the high-magnification field of view, the tumor cells
  were mainly spindle-shaped to polygonal cells with a high N/C ratio, and striated
  myoblasts were also found.
case_images: 10.1177_2050313X221116667-fig3.jpg
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case_images: fig3-2050313X221116667
case_images: Histologically, it was a tumor with a high cell density, and diffuse proliferation was obvious (Figure 3(a)). It was also conspicuous that the cells were arranged along the fibrotic septum (Figure 3(b)). The tumor cells were mainly spindle-shaped and polygonal with a high N/C ratio and mixed with striated myoblast-like cells with acidophilic cytoplasm (Figure 3(c)).
case_images: Immunostained images of MyoD1 (a), myogenin (b), desmin (c), and SMA (d).
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case_images: The tumor was positive for MyoD1, myogenin, and desmin (Figure 4(a)-(c)) and partly alpha-smooth muscle actin (alpha-SMA) positive (Figure 4(d)).
case_images: HE-stained images of the first surgical specimen. In the low-magnification field of
  view, stroma hyperplasia with foliate construction covered with atypical glandular
  epithelium with infarct (a) and polygonal metaplasia (b) were found. (c) In the
  medium-magnification field of view, the arrangement of tumor cells along the fibrous
  membrane was also found. (d) In the high-magnification field of view, the tumor cells
  were mainly spindle-shaped to polygonal cells with a high N/C ratio, and a mixture of
  acidophilic cytoplasm and striated myoblast-like cells with striated myoblasts was also
  found.
case_images: 10.1177_2050313X221116667-fig5.jpg
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case_images: fig5-2050313X221116667
case_images: Interstitial hyperplasia was seen with a leaf-like structure covered by a glandular epithelium with poor atypia and flat epithelial metaplasia epithelium (Figure 5(a) and (b)). In the area with a high cell density, diffuse proliferative images and cells arranged along the fibrotic septum could also be seen (Figure 5(c)). Similarly, the tumor cells were mainly spindle-shaped to polygonal with a high N/C ratio and mixed with acidic cytoplasm and striated myoblast-like cells (Figure 5(d)).