JPC SYSTEMIC PATHOLOGY

CARDIOVASCULAR SYSTEM

February 2025

C-M12

 

SIGNALMENT (JPC # 4033739): 2.5-year-old female spayed domestic short hair cat (Felis catus)

 

HISTORY: The animal was presented with a 6 week history of pica (licking coal) with a more recent history of reduced appetite and lethargy culminating to progressive deterioration of body condition. She was tachypneic and lethargic. An echocardiogram showed thickening of the left ventricular wall and interventricular septum, mild pericardial effusion, and moderate pleural effusion. 45ml of blood-tinged fluid was drained from the thorax. The fluid had a high protein count and clotted protein within the syringes. The respiratory rate improved but shortly after respiratory and cardiac arrest ensued.

 

HISTOPATHOLOGIC DESCRIPTION: Heart, cross section at the level of the ventricles: Multifocally, predominantly within the outer half of the myocardium of the left and right ventricles, 75% of small to medium sized vessels are transmurally expanded by a proliferation of concentrically to haphazardly arranged plump spindle cells that compress and occasionally occlude the vessel lumina, and frequently form small slit-like spaces that contain erythrocytes and occasional fibrin thrombi. Occasionally, these proliferative lesions are whorled with irregularly anastomosed vascular spaces, reminiscent of glomeruloid structures. The spindle cells have indistinct cell borders, a small to moderate amount of pale eosinophilic cytoplasm, and a single, irregularly ovoid nucleus with finely stippled chromatin and one to two indistinct nucleoli. Multifocally, cardiomyocytes are swollen with sarcoplasmic vacuolation (degeneration), shrunken and hypereosinophilic with loss of cross striations, fragmentation, and nuclear pyknosis or karyorrhexis (necrosis), or lost and replaced by fibrous connective tissue (fibrosis). Diffusely, cardiomyocytes are separated by increased clear space (edema) and multifocal mild hemorrhage. The epicardium is expanded by multifocal mild aggregates of lymphocytes, plasma cells, and fewer macrophages. 

 

MORPHOLOGIC DIAGNOSIS: Heart, arterioles: Atypical endothelial and pericyte proliferation (angioendotheliomatosis), chronic, diffuse, severe, with cardiomyocyte degeneration, necrosis, and myocardial fibrosis.

 

CONDITION: Feline systemic reactive angioendotheliomatosis

 

GENERAL DISCUSSION: 

• A rare, non-neoplastic proliferative disorder, primarily in cats, resulting in multifocal intravascular endothelial and pericyte proliferation of blood vessels throughout the body 
• Heart is the most commonly and severely affected organ; other commonly affected organs include kidneys, spleen, lymph nodes, gastrointestinal tract, brain, eyes, and pancreas
•  “Malignant angioendotheliomatosis,” an unrelated condition, is actually an intravascular lymphoma characterized by neoplastic lymphocytes proliferating within the lumens of blood vessels (not further discussed here) 

 

PATHOGENESIS:

• Unknown
• May be linked to infection with Bartonella spp. or to thrombotic thrombocytopenic purpura 

 

TYPICAL CLINICAL FINDINGS:

• Dependent on the site(s) involved; signs consistent with cardiac insufficiency and pulmonary edema are most common 
• +/- petechiae and ecchymoses 

 

TYPICAL GROSS FINDINGS: 

• Thoracic and/or pericardial effusion 
• Pulmonary edema 
• Cardiomegaly, splenomegaly 

 

TYPICAL LIGHT MICROSCOPIC FINDINGS:

• Intravascular endothelial and pericyte proliferation that partially or completely occludes vessels within multiple organs 
• Whorled, glomeruloid proliferations 
• +/- fibrin thrombi

 

DIFFERENTIAL DIAGNOSIS:

 

COMPARATIVE PATHOLOGY:

• Cattle: There is a single report in a steer with intraluminal proliferations of endothelial cells and pericytes, primarily in the heart, but also the liver, lung, lymph nodes, kidney, adrenal gland, and brain; this animal was persistently infected with bovine viral diarrhea virus (BVDV) and the intravascular proliferations were occasionally immunoreactive for BVDV
• Humans: Limited to the skin linked to Bartonella and termed bacillary angiomatosis

 

REFERENCES:

1. Marr J, Miranda IC, Miller AD, et al. A review of proliferative vascular disorders of the central nervous system of animals. Vet Pathol. 2021;58(5):864-880. 
2. Robinson WF, Robinson NA. Cardiovascular system. In: Maxie MG, ed. Jubb, Kennedy, and Palmer’s Pathology of Domestic Animals, Vol 3, 6th ed. St. Louis, MO: Elsevier; 2016:99.

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