JPC SYSTEMIC PATHOLOGY
REPRODUCTIVE SYSTEM
January 2019
R-N14 (NP)

Signalment (JPC# 2830560):  A 12-year-old spayed female greyhound

HISTORY:  This dog had a mass in the mammary gland area.

HISTOPATHOLOGIC DESCRIPTION:  Mammary gland:  Expanding and effacing the mammary gland is a 1 x 2 cm, unencapsulated, infiltrative, multilobulated neoplasm with multifocal areas of necrosis, hemorrhage, mineralization, and acicular (cholesterol) clefts.  The neoplasm incorporates and compresses adjacent ducts and elevates the overlying epidermis.  Lobules are separated by variably thick bands of collagen and are composed of polygonal to fusiform cells arranged in islands and solidly cellular areas supported by fine fibrovascular stroma.  Neoplastic cells have variably distinct cell borders and abundant eosinophilic vacuolated cytoplasm.  Larger vacuoles (up to 50 um in diameter) peripheralize the nucleus.  Nuclei are vesiculate with one prominent magenta nucleolus.  Mitoses average 5 per 10 HPF.  There is moderate anisokaryosis and anisocytosis.  Focally, cyst-like spaces are lined by attenuated to cuboidal neoplastic cells and contain homogenous eosinophilic material and cellular debris.  Multifocally, there is scattered single cell necrosis, mineral, and small foci of cartilaginous metaplasia with neoplastic cells in lacunae.  In the surrounding tissue, there are low numbers of lymphocytes and plasma cells.  There is mild epidermal orthokeratotic hyperkeratosis.

MORPHOLOGIC DIAGNOSIS:  Mammary gland:  Malignant myoepithelioma, greyhound, canine.

SYNONYM:  Spindle cell carcinoma

GENERAL DISCUSION:

PATHOGENESIS:

TYPICAL CLINICAL FINDINGS:

TYPICAL GROSS FINDINGS:

TYPICAL LIGHT MICROSCOPIC FINDINGS:

Malignant myoepithelioma:

Myoepithelioma:

Spindle cells in short bundles surrounded by myxoid matrix

Similar basic features as malignant counterpart but minimal anisocytosis and anisokaryosis and low mitotic index

ADDITIONAL DIAGNOSTIC TESTS:

DIFFERENTIAL DIAGNOSIS: 

Benign mammary tumors:

Malignant mammary tumors:

COMPARATIVE PATHOLOGY:

REFERENCES:

  1. Barthold SW, Griffey SM, Percy DH. Pathology of Laboratory Rodents and Rabbits. 4th ed. Ames, IA: Blackwell Publishing; 2016:3, 114.
  2. Destexhe E, Lespagnard L, Degeyter M, Heymann R, Coignoul F. Immunohistochemical identification of myoepithelial, epithelial, and connective tissue cells in canine mammary tumors. Vet Pathol. 1993;30:146-154.
  3. Dore M, Lanthier I, Sirois J. Cyclooxygenase-2 expression in canine mammary tumors. Vet Pathol. 2003;40:207-212.
  4. Gama A, Alves A, Gartner F, Schmitt F. p63: A novel myoepithelial cell marker in canine mammary tissues. Vet Pathol. 2003;40:412-420.
  5. Goldschmidt M, Pena L, Rasotto R, Zappulli. Classification and grading of canine mammary tumors. Vet Pathol. 2011;48(1):117-131.
  6. Grandi F, Colodel M, Rocha R, Sequeira J. Sebaceous metaplasia in a canine mammary gland non-infiltrative carcinoma with myoepithelial component. J VET Diagn Invest. 2011;23:1230.
  7. Heller DA, Clifford CA, Goldschmidt MH, et al. Cyclooxygenase-2 expression is associated with histologic tumor type in canine mammary carcinoma. Vet Pathol. 2005;42:776-780.
  8. Meuten DJ. Tumors in Domestic Animals, 5th ed. Ames, IA: John Wiley & Sons, Inc.; 2017:752.
  9. Ramalho LNZ, Ribeiro-Silva A, Cassali GD, Zucoloto S. The expression of p63 and cytokeratin 5 in mixed tumors of the canine mammary gland provides new insights into the histogenesis of these neoplasms. Vet Pathol. 2006;43:424-429.
  10. Rasotto R, Goldschmidt MH, Castagnaro M, Carnier P, Caliari D and Zappulli V. The dog as a natural animal model for study of the mammary myoepithelial basal cell lineage and its role in mammary carcinogenesis. J Comp Path. 2014;151:166-180.
  11. Schlafer DH, Foster RA. Female genital system. In: Maxie MG, ed. Jubb, Kennedy, Palmer’s Pathology of Domestic Animals. Vol 3. Philadelphia, PA: Elsevier Saunders; 2016:460-464.
  12. Sorenmo K. Canine mammary tumors. In: Kitchell BE, ed. Vet Clin Small Anim. Philadelphia, PA: Elsevier; 2003;33:573-596.
  13. Yang X, Hori T, Fukuds A, et al. Malignant myoepithelioma with a squamous epithelial component in the mammary gland of a cynomolgus monkey. Tox Path. 2003; 31:549-553.


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