JPC SYSTEMIC PATHOLOGY

INTEGUMENTARY SYSTEM

September 2016

I-M19

 

Signalment (JPC# 2507404):  Adult male Sprague-Dawley rat

HISTORY:  This rat was in the control group of a subchronic toxicity study. Gross morphological changes were limited to bilaterally enlarged pinnae.

HISTOPATHOLOGIC DESCRIPTION:  Pinna:  The pinna is thickened up to 5mm by nodules of disrupted and disorganized auricular cartilage.  In some areas, cartilage is characterized by thick, irregular islands of amphophilic cartilaginous matrix surrounding aggregates of closely approximated chondrocyte lacunae (chondromatous regeneration).  Occasionally, islands of cartilage exhibit loss of basophilic staining within the matrix (degeneration) or are fragmented with shrunken, hypereosinophilic, pyknotic chondrocytes or empty lacunae (necrosis).  Diffusely infiltrating the dermis and separating and surrounding myocytes, as well as multifocally infiltrating the perichondrium and disrupting auricular cartilage, is an inflammatory infiltrate composed of many viable neutrophils, macrophages, lymphocytes, plasma cells and few Langhans-type multinucleated giant cells, admixed with reactive fibroblasts, immature fibrous connective tissue and small caliber blood vessels (granulation tissue) progressing to more mature fibrous connective tissue.  Multifocally, the cartilage matrix is replaced by eosinophilic, homogenous material that surrounds osteocytes within lacunae, and contains extensive areas of basophilic, angular to granular mineralized matrix (osseous metaplasia).  Osteoblasts and multinucleated osteoclasts surround these metaplastic islands and trabeculae of woven bone which also contain bone marrow.  Multifocally, dermal collagen fibers are loosely arranged and separated by an eosinophilic amorphous material and lymphatics are moderately ectatic and filled with eosinophilic proteinaceous fluid (edema).  The overlying epidermis is mildly hyperplastic with mild acanthosis and intracellular edema.

MORPHOLOGIC DIAGNOSIS:  Pinna, cartilage:  Degeneration, multifocal, moderate, with cartilaginous regeneration, fibroplasia, osseous metaplasia and granulomatous dermatitis, Sprague-Dawley rat, rodent.

ETIOLOGIC DIAGNOSIS:  Idiopathic auricular chondritis

CONDITION:  Auricular chondritis

GENERAL DISCUSSION: 

PATHOGENESIS:

TYPICAL CLINICAL FINDINGS: 

TYPICAL GROSS FINDINGS: 

TYPICAL LIGHT MICROSCOPIC FINDINGS: 

ADDITIONAL DIAGNOSTIC TESTS: 

COMPARATIVE PATHOLOGY: 

REFERENCES: 

  1. Chiu T, and Lee KP. Auricular chondropathy in aging rats. Vet Pathol. 1984;21(5):500-504.
  2. Khan AJ, Lynfield Y, Baldwin H. Relapsing polychondritis: Case report and review of the literature. 1994;54(2):98‑100.
  3. Kitagaki, M, Suwa T, Yanagi M, Shiratori K. Auricular chondritis in young ear-tagged Crj:CD (SD)IGS rats. Lab Anim Sci. 2003; 37(3): 249-253.
  4. Kitagaki M. and Hirota M. Auricular chondritis caused by metal ear tagging in C57BL/6 mice. Vet Pathol. 2007; 44:458-466.
  5. Linton CG, Gordon BE, Richardson JA. Diagnostic exercise: Thickened auricular pinnae in a Sprague Dawley rat. Lab Anim Sci. 1994; 44(1):69-70.
  6. McEwen BJ, Barsoum NJ. Auricular chondritis in Wistar rats. Lab Anim Sci. 1990; 24(3):280-283.
  7. Meingassner JG. Sympathetic auricular chondritis in rats: A model of autoimmune disease. Lab Anim Sci. 1991; 25:68-78.
  8. Percy DH, Barthold SW. Rat. In: Pathology of Laboratory Rodents and Rabbits. 4th ed. Ames, IA: Blackwell Publishing; 2016:159-160.
  9. Yoshitomi K, Brown HR. The ear and pinna. In: Boorman G, Eustis S, Elwell MR, Montgomery CA, MacKenzie WF, eds. Pathology of the Fischer Rat. New York, NY:Academic Press; 1990: 227-238.


Click the slide to view.



Click on image for diagnostic series.



Back | Home | Contact Us | Links | Help |