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Case Reports
. 2024 Jun 19;86(6):684-688.
doi: 10.1292/jvms.23-0506. Epub 2024 Apr 19.

Benign mixed mammary tumor with sebaceous differentiation in a dog

Ying Ma  1 , Junchao Shi  1 , Huijun Lu  1 , Jing Zhang  1 , Zheng Liu  1 , Jianwei Wei  1 , Kui Zhao  1 , Feng Gao  1 , Wenqi He  1
Affiliations
Case Reports

Benign mixed mammary tumor with sebaceous differentiation in a dog

Ying Ma et al. J Vet Med Sci. .

Abstract

We describe here a case of canine mammary benign mixed tumor with sebaceous metaplasia in the right fifth mammary gland of an eight-year-old, intact female Poodle dog. Grossly, the mass was firm with off-white, poorly lobulated cut surfaces. Histologically, the luminal epithelial cells and myoepithelial cells proliferated with cartilage formation and focal squamous metaplasia. Moreover, a large number of nests of various sizes, which were filled with foamy cells in the center and associated with basaloid reserve-like cells in the periphery, showed sebaceous gland-like structures. Immunohistochemically, myoepithelial cells and reserve-like cells in the metaplastic sebaceous gland-like structures were CK14, α-smooth muscle actin (α-SMA) and p63 positive, suggesting a possibility that these two components may have a common cell of origin.

Keywords: benign mixed tumor; canine; mammary gland; sebaceous metaplasia.

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Conflict of interest statement

The authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Figures

Fig. 1.
Fig. 1.
Gross appearance of the mass. (A) The mass is white and irregular-shaped. Bar=5 mm. (B) The cut surface of the mass is white and poorly lobulated. Bar=5 mm.
Fig. 2.
Fig. 2.
Histologic features of canine mammary benign mixed tumor with sebaceous and squamous differentiation. (A) The tumor is well-demarcated, lobulated and encapsulated by fibrous connective tissue. H&E. Bar=1,000 μm. (B) The luminal epithelial cells (black arrow) and myoepithelial cells (red arrow) proliferate and the ductal epithelial cells (yellow arrow) have a finger-like growth pattern. H&E. Bar=100 μm. (C) The luminal epithelial cells are arranged in tubules and myoepithelial cells are surrounded by variable amounts of lightly basophilic myxoid matrix. H&E. Bar=50 μm. (D) Well differentiated chondrocytes within the cartilage lacuna in the area of cartilaginous metaplasia (black arrowheads). H&E. Bar=50 μm. (E) Sebaceous gland–like nests are surrounded by basaloid reserve-like cells (asterisk). H&E. Bar=200 μm. (F) Sebaceous gland–like structures (asterisk) and focal squamous cells (red arrowhead) closely align with the ductular structures. H&E. Bar=50 μm.
Fig. 3.
Fig. 3.
Histochemical and immunohistochemical staining. (A) Alcian blue is positive in the myxoid area (white arrow) and Periodic acid-Schiff (PAS) is negative in the sebaceous gland-like structures (black arrow). Bar=50 μm. Inset: alcian blue in the cartilaginous area is positive. Bar=50 μm. (B) Toluidine blue is positive in the myxoid area. Bar=100 μm. Inset: High magnification of the Toluidine blue-positive aera. Bar=100 μm. (C) Sebaceous components and myoepithelial cells are positive for cytokeratin 14 (CK14). Bar=50 μm. (D and E) Luminal epithelial cells are CK18- and CK19-positive. Bar=50 μm. (F) Myoepithelial cells, squamous cells and some basaloid reserve–like cells in the sebaceous components stain positively for p63. Bar=50 μm. (G) Myoepithelial cells and sebaceous reserve–like cells stain positively for α-smooth muscle actin (α-SMA). Bar=50 μm. (H) Myoepithelial cells are positive for cluster of differentiation 10 (CD10). Bar=50 μm.
See this image and copyright information in PMC

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