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Case Reports
. 2017 Jul;30(3):245-250.
doi: 10.1293/tox.2016-0080. Epub 2017 Apr 27.

A spontaneous myoepithelial carcinoma in the mammary gland of an aged female ICR (CD-1) mouse

Tsuyoshi Ito  1 , Toshinori Yoshida  2 , Katsumi Soma  1 , Yoshitaka Katoh  1 , Yuko Shimada  1 , Aya Ohnuma-Koyama  1 , Naofumi Takahashi  1 , Yoshimasa Okazaki  1 , Atsushi Shiga  1 , Maki Kuwahara  1 , Takanori Harada  1
Affiliations
Case Reports

A spontaneous myoepithelial carcinoma in the mammary gland of an aged female ICR (CD-1) mouse

Tsuyoshi Ito et al. J Toxicol Pathol. 2017 Jul.

Abstract

We report a female Crlj:CD1(ICR) mouse with a spontaneous mammary gland tumor composed of biphasic tumor cells, i.e., epithelioid and spindle-shaped myoepithelial cells. Macroscopically, a subcutaneous mass, approximately 3 cm in diameter was found in the lumbodorsal region. Histopathologically, the epithelioid cells proliferated in an alveolar or nest-like growth pattern, occasionally forming glandular-like structures. On the other hand, the spindle-shaped cells proliferated in a sarcomatous pattern. Normal mammary gland was observed in the vicinity of the tumor. Both types of tumor cells showed immunoreactivity for cytokeratin (wide spectrum screening), vimentin, S100, and p63. In addition, the epithelioid cells and spindle-shaped cells were immunopositive for glial fibrillary acidic protein and smooth muscle actin, respectively. Moderate atypia, high proliferative activity, massive necrosis, and partial infiltration to the surrounding tissues were also observed. We made a diagnosis of myoepithelial carcinoma, which is extremely rare in ICR mice.

Keywords: ICR mouse; mammary gland tumors; myoepithelial carcinoma; myoepithelial cells; spontaneous tumor.

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Figures

Fig. 1.
Fig. 1.
Histopathological findings of the subcutaneous tumor in the lumbodorsal region. (A) Biphasic proliferation of epithelioid cells in an alveolar or nest-like growth pattern and spindle-shaped cells in a sarcomatous growth pattern. The epithelioid cells had relatively abundant eosinophilic cytoplasm with round to ovoid nuclei, while spindle-shaped cells had ill-defined eosinophilic cytoplasm with spindle-shaped nuclei. (B) Glandular-like structures composed of epithelioid cells. (C) Multinucleated cells (arrows) were sometimes observed and were mixed in with the spindle-shaped cell-proliferating area. H&E. Bar = 50 μm (A), 20 μm (B, C).
Fig. 2.
Fig. 2.
Immunohistochemical findings of epithelioid cells and spindle-shaped cells of the tumor. The epithelioid cells and spindle-shaped cells were positive (A) and positive in a limited population (B) for cytokeratin (wide spectrum screening), respectively. The epithelioid cells and spindle-shaped cells were positive in a limited population (C) and positive (D) for vimentin, respectively. The glandular-like structures composed by the epithelioid cells (inset in C) and multinucleated cells among the spindle-shaped cells (arrows in D) were also positive for vimentin. Although in a limited population, the epithelioid cells and spindle-shaped cells were positive (E) and weakly positive (F) for p63, respectively. GFAP was positive in only epithelioid cells (G). Bar = 20 μm (A–F), 50 μm (G).
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