PMC8110257_01
(A, B) The common axial position and oblique lateral position of the left breast with molybdenum targeting showing breast-occupying lesions. BI-RADS was used for classification into three categories. (C) The surgical specimen was breast tissue with spinal skin and nipple (15 cm x 11 cm x 6.5 cm). The size of the spinal skin sample was 11 cm x 6.5 cm, and a nodule with a size of 8 cm x 6 cm x 5.5 cm was found under the nipple with multiple cuts. The nodules and surrounding mammary glands were clear. The nodules were gray and grayish yellow. Some areas showed cystic changes, some were solid and lobulated, and some were dark red, suggestive of necrosis.
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Imaging of space-occupying lesions in the left breast was performed using the Breast Imaging-Reporting and Data System (BI-RADS) classification into three categories (Figure 1A). On the cut surface, a nodule measuring 8 cm x 6 cm x 5.5 cm was found under the nipple and showed clear boundaries with surrounding tissue (Figure 1C).
Microphotographs showing the histopathological features of the tumor. (A) The tumor had loose and dense cell areas (H&E; 40x). The first arrow points to dense cell areas, and the second arrow points to loose cell areas. (B) PT area (H&E; 40x). (C) Fibroadenoma area around the malignant PT (H&E; 40x). (D) Residual ductal epithelium (H&E; 200x). (E) Mucinous background (H&E; 100x). (F) Vascular rich area (H&E; 100x). (G) Adipocytes (H&E; 400x). (H) Odd megakaryocytes (H&E; 200x). (I) Rosette-like cells (H&E; 100x).
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The tumor had loose and dense cell areas (Figure 2A), a cell-rich mesenchyme covered the epithelium, and the myoepithelium protruded into the sac cavity to form a leaf-like structure under low magnification (Figure 2B). Fibroadenoma areas could be seen around the cell-rich area (Figure 2C). Residual ducts were surrounded by a cell-rich area (Figure 2D). In the loose mucus area, there were many stellate cells and spindle cells (Figure 2E), and there was a characteristic thin, branching vascular pattern, resembling "chicken wire." The cells around the blood vessels were mostly round, oval, or short spindle-shaped primitive mesenchymal cells, essentially demonstrating the same shape (Figure 2F). There were more adipocytes and oddly shaped megakaryocytes in the cell-rich area (Figure 2G), and different degrees of interstitial collagenization were detected. Moreover, the cells showed obvious atypia and were arranged into rosettes (Figure 2I).
(A) A few tumor cells were AE1/3 positive (original magnification: 200x). (B) Tumor cells were diffusely positive for vimentin (original magnification: 200x). (C) Tumor cells were negative for E-cadherin and S-100 (D) (original magnification: 200x). Tumor cells were diffusely, strongly positive for p16 (E), CDK4 (F), and MDM2 (G) (original magnification: 200x). (H) Immunohistochemical staining for Ki-67 showed a labeling index of greater than 90% (original magnification: 100x). (I) The FISH test results showed that MDM2 was not amplified.
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Based on immunostaining, only a few tumor cells were positive for AE1/3 (Figure 3A) and vimentin (Figure 3B), whereas staining for cytokeratin (CK) 34betaE12, E-cadherin (Figure 3C), p63, and S-100 (Figure 3D) was negative, supporting the diagnosis of PT. Tumor mesenchymal cells were positive for vimentin (Figure 3B) and smooth muscle actin, suggesting that tumor cells were the source of mesenchymal cells. Interestingly, immunohistochemical staining was diffusely positive for p16 (Figure 3E), mouse double minute 2 (MDM2; Figure 3F), and cyclin-dependent kinase 4 (CDK4; Figure 3G). Additionally, proliferating cells were positive for the proliferative marker Ki-67, and the labeling index was more than 90% (Figure 3H). However, the fluorescence in situ hybridization (FISH) test results showed that MDM2 was not amplified (Figure 3I).