SEVPAC 2013

Case Number 12-114902

An Enlarging Pectoral Mass in a Thoroughbred Horse

Permission granted only for viewing on SEVPAC website

Stephanie M. Shrader, DVM1

Richard C. Weiss, VMD, PhD1

Fred Caldwell, DVM, DACVS2

1Department of Pathobiology2Department of Clinical Sciences Auburn University College of Veterinary Medicine

• 9-year-old, male castrated, Thoroughbred horse

• Firm mass extending from the right pectoral region to the right thoracic wall

• Kicked in this region by another horse several months prior to presentation

• Size of mass waxes and wanes • Painful on palpation• Starting to cause abduction of the scapula and

gait alteration

Signalment and History



Image courtesy of Fred Caldwell, DVM, MS,

DACVS

• Ultrasound of the mass – mixed echogenicity• rDVM submitted samples for culture:

• Acinetobacter baumannii• Alpha hemolytic Streptococcus• Raoultella planticola

• Incisional biopsy diagnosed as a possible soft tissue sarcoma

• Corynebacterium pseudotuberculosis titer was negative @1:8

Other Diagnostics Performed



1x, H&E


1x, Trichrome


20x, H&E


20x, Trichrome

Musculoaponeurotic fibromatosis (desmoid tumor), diffuse, marked, chronic

Morphologic Diagnosis


• First reported in a horse in 1983 (Ihrke et al., JAVMA, 183:10;1100-1102)

• Prior to that, reported as a rare non-metastasizing fibrous neoplasm in people

• Occurs in mid-cervical region of the neck and pectoral region

• Intralesional fluid-filled cavities associated with sterile inflammation have been described


Musculoaponeurotic fibromatosis (desmoid tumor)


• Criteria for diagnosis in people:• Hypocellular, unencapsulated, infiltrative mass• Composed of bands of mature fibrous tissue • Deep location and relationship to a musculoponeurotic

system• Diffuse growth with engulfment of muscle fibers

• Unknown etiology• Possibly secondary to trauma

• Prognosis• Variable

Musculoaponeurotic fibromatosis (desmoid tumor)

• Pool, R.R. (1990): Tumors and tumor-like lesions of joints and adjacent soft tissues. In Moulton, J.E. (ed). Tumors in Domestic Animals. 3rd ed. University of California Press, Berkley, 129-30.

• Cooper, B.J. and Valentine, B.A. (2002): Tumors of Muscle. In Meuten, D.J (ed). Tumors in Domestic Animals. 4th ed. Iowa State Press, Blackwell Publishing Company, Ames, 360-1.

• Ihrke P.J., et al, Fibromatosis in a Horse. JAVMA. 1983;183:1100-2.

• Valentine, B.A., et al., Intramuscular Desmoid Tumor (Musculoaponeurotic Fibromatosis) in Two Horses. Veterinary Pathology. 1999;36(5):468-70.

References


• Dr. Weiss• Dr. Caldwell• Histopathology

laboratory• My fellow residents

And a Special Thanks To…


SEVPAC 2013

Documents

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