JPC SYSTEMIC PATHOLOGY

INTEGUMENT SYSTEM

November 2016

I-V09

 

Signalment (JPC #1851282):  8-week-old male New Zealand white rabbit

HISTORY:  This rabbit developed a single large nodular cutaneous mass on the top of the head that grew rapidly over a 3-week period.

HISTOPATHOLOGIC DESCRIPTION:  Haired skin:  Markedly expanding the dermis, abutting the overlying epidermis, separating and replacing adnexa, and extending to cut borders, is a densely cellular proliferation of interlacing streams and bundles of spindle cells separated by a moderate collagenous matrix.  Spindle cells have indistinct cell borders, a moderate amount of pale, eosinophilic, fibrillar to microvacuolated cytoplasm that infrequently contain 4‑10um diameter, round, eosinophilic intracytoplasmic viral inclusion bodies.  Nuclei are round to oval, vesiculate with finely stippled chromatin and contain 1 to 3 variably distinct nucleoli.  The mitotic rate averages 1/HPF, and there is moderate anisokaryosis.  Scattered throughout the spindle cell proliferation and more pronounced at the periphery are aggregates of moderate numbers of lymphocytes, plasma cells, heterophils, and macrophages.  The epidermal and follicular epithelium is moderately hyperplastic with multifocal areas of ballooning degeneration, and epithelial cells rarely contain 4 to10um eosinophilic intracytoplasmic viral inclusion bodies.  There is a focal intracorneal pustule. 

MORPHOLOGIC DIAGNOSIS:  Haired skin:  Atypical mesenchymal proliferation, dermal, diffuse, marked, with chronic-active dermatitis, epidermal hyperplasia, epithelial ballooning degeneration, and epithelial and mesenchymal eosinophilic intracytoplasmic inclusion bodies, New Zealand White rabbit (Oryctolagus cuniculus), lagomorph.

ETIOLOGIC DIAGNOSIS: Leporipoxviral fibroma

CAUSE:  Rabbit (Shope) fibroma virus

CONDITION:  Rabbit fibromatosis

SYNONYMS:  Shope fibroma

SLIDE B
SIGNALMENT(JPC #1850942):  Gray squirrel

HISTORY:  This squirrel had cutaneous tumor-like lesions involving the ears, lips, face, footpads, genital orifices, and perianal region.

HISTOPATHOLOGIC DESCRIPTION:  Haired skin:  Markedly expanding the dermis and extending to the epidermis and cut borders is a multilobulated, densely cellular proliferation of spindle cells arranged in streams and bundles and separated by a moderate collagenous matrix.  Spindle cells have indistinct cell borders, a moderate amount of eosinophilic fibrillar cytoplasm, and often contain a 5-10um, round, intracytoplasmic, brightly eosinophilic viral inclusion body.  Nuclei are irregularly round to oval, have moderately stippled chromatin, and indistinct nucleoli.  The mitotic rate averages 1/10 HPF.  There are few scattered multinucleated viral syncitial cells, with up to 10 nuclei, which occasionally have intracytoplasmic viral inclusions.  There is a prominent band of lymphocytes surrounding lobules of spindle cells and, more diffusely throughout the dermis, lymphocytes are admixed with plasma cells, macrophages, and neutrophils.  There is marked epithelial ballooning degeneration and epithelial cells frequently contain 10um diameter eosinophilic intracytoplasmic viral inclusion bodies.  There is diffuse mild parakeratotic hyperkeratosis and multifocal intracorneal pustules.

MORPHOLOGIC DIAGNOSIS:  Haired skin:  Atypical mesenchymal proliferation, dermal, multifocal to coalescing, with chronic-active dermatitis, epidermal hyperplasia, epithelial ballooning degeneration, and epithelial and mesenchymal eosinophilic intracytoplasmic viral inclusion bodies, Eastern gray squirrel (Sciurus carolinensis), rodent.

ETIOLOGIC DIAGNOSIS:  Leporipoxviral fibroma

CAUSE:  Squirrel fibroma virus

CONDITION:  Squirrel fibromatosis

GENERAL DISCUSSION: 

Rabbit fibroma virus

Squirrel fibroma virus

PATHOGENESIS:

Rabbit fibroma virus

Squirrel fibroma virus

TYPICAL GROSS FINDINGS: 

Rabbit fibroma virus

Squirrel fibroma virus

TYPICAL LIGHT MICROSCOPIC FINDINGS:

Rabbit fibroma virus

Squirrel fibroma virus

ULTRASTRUCTURAL FINDINGS: 

DIFFERENTIAL DIAGNOSIS:

Rabbit fibroma virus

Viral diseases that cause similar gross lesions in rabbits:

Squirrel fibroma virus

COMPARATIVE PATHOLOGY:

Fibromas caused by viruses in other species:

Leporipoxviruses:

References:

  1. Bangari DS, Miller MA, Stevenson GW, Thacker HL, Sharma A, Mittal SK. Cutaneous and systemic poxviral disease in red (Tamiasciurus hudsonicus) and gray (Sciurus carolinensis) squirrels. Vet Pathol. 2009;46(4):667-72.
  2. Barthold SW, Griffey SM, Percy DH. Pathology of Laboratory Rodents and Rabbits. 4th ed.  Ames, IA; 2016: 263-264.
  3. Bomhard W, Goldschmidt MH, Shofer FS, Perl L, Rosenthal KL, Mauldin EA. Cutaneous neoplasms in pet rabbits: A retrospective study. Vet Pathol. 2007;44:579-588.
  4. Himsworth CG, Musil KM, Bryan L, Hill JE. Poxvirus infection in an American red squirrel (Tamiasciurus hudsonicus) from northwestern Canada. J Wild Dis. 2009;45(4):1143-9.
  5. Mauldin EA, Peters-Kennedy J. Integumentary system.  In: Maxie MG, ed. Jubb, Kennedy, and Palmer’s Pathology of Domestic Animals. Vol 1. 6th ed. New York, NY: Elsevier Limited; 2015:616.
  6. Miller WH, Griffin CE, Campbell KL. Muller & Kirk’s Small Animal Dermatology, 7th St. Louis, MO: Elsevier Limited; 2013: 867. 
  7. Quesenberry KE, Carpenter JW. Ferrets, Rabbits, and Rodents Clinical Medicine and Surgery, 3rd  St. Louis, MO: Elsevier Limited; 2012: 240.
  8. Rivas AE, Righton AL, Bugman AM, Kihn AE, Coleman DA, Singh K, Whittington JK. Pathology in practice: Cutaneous and disseminated infection with squirrel fibroma virus (SFV).  J Am Vet Med Assoc.  2014;245(4): 389-391.
  9. Suckow MA, Stevens KA, Wilson RP. The laboratory rabbit, guinea pig, hamster, and other rodents, 1st  Waltham, MA: Academic Press; 2012: 373-376.
  10. Terrell SP, Forrester DJ, Mederer H, Regan TW. An epizootic of fibromatosis in gray squirrels (Sciurus carolinensis) in Florida. J Wild Dis. 2002;38(2):305-312.
  11. Williams ES, Barker IK. Infectious Diseases of Wild Mammals. 3rd ed. Ames, IA:Iowa State University Press; 2001:182-190.


Click the slide to view.



Click on image for diagnostic series.



Back | Home | Contact Us | Links | Help |