October 2016



Slide A
Signalment (JPC 2799364): Age and breed unspecified cat


HISTOPATHOLOGIC DESCRIPTION: Subcutis (per contributor): Infiltrating the subcutis and compressing the panniculus carnosus is a 1.0 x 0.8 cm, unencapsulated,  multilobulated, moderately cellular neoplasm composed of spindle cells arranged in long interlacing streams and bundles separated by fibromyxomatous matrix.  Neoplastic cells have indistinct borders, a small amount of eosinophilic fibrillar cytoplasm, with an oval to elongate nucleus, finely stippled chromatin and1-3 prominent magenta nucleoli.  There is moderate anisokaryosis with multifocal single cell necrosis. The mitotic count, averages 1 per 400x HPF.  There are multifocally peripheral are perivascular aggregates of macrophages, often-containing blue-gray clumped intracytoplasmic granular material (vaccine material) admixed with aggregates of lymphocytes, and fewer plasma cells and neutrophils.  There is rare degeneration and atrophy of subjacent myocytes.

MORPHOLOGIC DIAGNOSIS: Subcutis (per contributor):  Vaccine-associated fibrosarcoma, breed unspecified, feline.

CAUSE: Post-vaccination reaction – Rabies or FeLV

SYNONYMS:  Feline injection site sarcoma, Postvaccinal fibrosarcomas

Slide B
Signalment (JPC 2800486): A domestic longhair cat


HISTOPATHOLOGIC DESCRIPTION: Subcutis(per contributor): Within the subcutis there is an 8 x 10 mm nodule with a central pseudocyst containing anastomosing trabeculae composed of eosinophilic lamellated amorphous polymerized fibrin admixed with necrotic debris and areas of drop-out (lytic necrosis).  The pseudocyst is rimmed by granulation tissue composed of loosely arranged reactive fibroblasts and small caliber blood vessels lined by reactive endothelial cells that are frequently arranged perpendicular to the surrounding fibrous connective tissue. The pseudocyst is further surrounded by abundant fibrosis, high numbers of large epithelioid macrophages filled with amphophilic granular material (vaccine material), moderate numbers of eosinophils, and nodular perivascular aggregates of lymphocytes.  Rarely, there are foreign body and Langhans type multinucleated giant cells. 

MORPHOLOGIC DIAGNOSIS:  Subcutis: Panniculitis, granulomatous , focally extensive, marked, with central pseudocyst, granulation tissue, and intrahistiocytic vaccine material, domestic longhair, feline.

CONDITION: Post-injection panniculitis; Vaccine-associated granuloma











  1. Bartholomew PM, Kreeger JM, Morton D. Injection-site malignant fibrous histiocytomas in a pegvisomant carcinogenicity study in SD Rats. Toxicol Pathol. 2014; 42(7):1082-1091.
  2. Bell CM, Schwarz T, Dubielzig RR. Diagnostic features of feline restrictive orbital myofibroblastic sarcoma. Vet Pathol. 2011; 48:742-750.
  3. Dore’ M. Cyclooxygenase-2 expression in animal cancers. Vet Pathol. 2011; 48(1):254- 265.
  4. Gross TL, Ihrke PJ, Walder EJ. Other mesenchymal tumors. In: Gross TL, ed. Skin Diseases of the Dog and Cat, 2nd ed. Ames, Iowa: Blackwell Science; 2005:797-801.
  5. Gumber S, Wakamatsu N. Vaccine-associated fibrosarcoma with keloidal differentiation in a cat. J Vet Diagn Invest. 2011; 23(5):1061-1064.
  6. Hendrick MJ, Mahaffey EA, Moore FM, Vos JH, Walder EJ. Histological classification of mesenchymal tumors of skin and soft tissues of domestic animals. In: Schulman FY, ed. World Health Organization, International Histological Classification of Tumors of Domestic Animals, 2nd ed., vol. 2, American Registry of Pathology, Washington, DC, 1998: 17, 38-39.
  7. Labelle AL, Labelle P. Canine ocular neoplasia: a review. Vet Ophthalmol. 2013;16:3-14.
  8. Labelle P. The eye. In: Zachary JF, ed. Pathologic Basis of Veterinary Disease. 6th ed. St. Louis, MO: Mosby Elsevier; 2016: 1306.
  9. Madewell BR, Griffey SM, McEntee MC, Leppert VJ, Munn RJ. Feline vaccine-associated fibrosarcoma: an ultrastructural study of 20 tumors (1996-1999). Vet Pathol. 38: 2001: 196-202.
  10. Maudlin EA, Peters-Kennedy J. Integumentary system. In: Maxie MG, ed. Jubb, Kennedy, and Palmer’s Pathology of Domestic Animals. Vol 1. 6th ed. Philadelphia, PA: Elsevier Saunders; 2016: 560, 725.
  11. McPherson L, et al. Intraocular sarcomas in two rabbits. J Vet Diagn Invest. 2009; 21(4):547-551.
  12. Munday JS, Stedman NL, Richey LJ. Histology and immunohistochemistry of seven ferret vaccination-site fibrosarcomas. Vet Pathol. 2003; 40(3):288-293.
  13. Raskin RE. Skin and subcutaneous tissues. In: Raskin RE, Meyer DJ, ed. Canine and Feline Cytology. 3rd ed. St. Louis, MO: Elsevier; 2016:67.
  14. Riedl M, Truyen U, Reese S, Hartmann K. Prevalence of antibodies to canine parvovirus and reaction to vaccination in client-owned, healthy dogs. Vet Rec. 2015; 177(23):597.
  15. Roccabianca P, et al. Cutaneous lymphoma at Injection sites: pathological, immunophenotypical, and molecular characterization in 17 cats. Vet Pathol. 2016; 53(4): 823-832.
  16. Shaw SC, Kent MS, et al. Temporal changes in characteristics of injection-site sarcomas in cats: 392 cases (1990-2006). J Am Vet Med Assoc. 2009; 234: 376-380.
  17. Srivastav A, Kass PH, McGill LD, Farver TB, Kent MS. Comparative vaccine-specific and other injectable-specific risks of injection-site sarcomas in cats. J Am Vet Med Assoc. 2012; 241(5):595-602.
  18. Thomasy SM, et al. Restrictive orbital myofibroblastic sarcoma in a cat--cross-sectional imaging (MRI & CT) appearance, treatment, and outcome. Vet Ophthalmol. 2013; 16 Suppl:123-129.
  19. Wilcock BP, Njaa BL. Special senses. In: Maxie MG, ed. Jubb, Kennedy, and Palmer’s Pathology of Domestic Animals. Vol 1. 6th ed. Philadelphia, PA: Elsevier Saunders; 2016: 486.
  20. Zeiss CJ, et al. Feline intraocular tumors may arise from transformation of lens epithelium. Vet Pathol 2003;40(4):355-362.

Click the slide to view.

Click on image for diagnostic series.

Back | Home | Contact Us | Links | Help |