JPC SYSTEMIC PATHOLOGY
Signalment (JPC #2417289): One week-old holstein calf
HISTORY: This calf was clinically normal and sacrificed for the collection of cardiac tissue for experimental purposes.
HISTOPATHOLOGIC DESCRIPTION: Heart: Subjacent to the endocardium, extending into the myocardium, and within one of the papillary muscles are two expansile, unencapsulated, well demarcated masses up to 0.75 cm x 1.5 cm that separate, surround, isolate and replace individual cardiomyocytes and Purkinje fibers. The masses are composed of multiple variably sized acini and tubules that measure up to 2.5 mm diameter and are lined by one to multiple layers of squamous to cuboidal epithelium with scant amount of eosinophilic cytoplasm, round to oval nuclei with no mitoses or atypia. Between the tubules, there are multifocal small nests of similar epithelial cells and abundant collagenous connective tissue. The interstitial tissue subjacent to the endocardium is mildly separated by clear space (edema).
MORPHOLOGIC DIAGNOSIS: Heart, myocardium: Epithelial inclusions, multifocal, holstein, bovine.
CONDITION: Myocardial epithelial inclusions
- Bovine myocardial epithelial inclusions are congenital masses that do not proliferate, metastasize, or undergo malignant transformation
- Incidental finding that usually occurs in the left ventricular free wall, less common in the interventricular septum
- Closely resemble benign adenomatoid tumors of humans which are of mesothelial origin
- Can be considered a choristoma; may be endodermal in origin from the foregut misplaced during organogenesis
- Unknown – may be a benign neoplasm or embryologic rest
TYPICAL CLINICAL FINDINGS:
TYPICAL GROSS FINDINGS:
- Single to multiple, well-circumscribed firm, plaque-like mass in the left ventricular wall and, less commonly, the interventricular septum
- Affected area is discolored or spongy
TYPICAL LIGHT MICROSCOPIC FINDINGS:
- Lesions composed of squamous to cuboidal epithelial cells that form tubular, ductular, and acinar structures; lumina may be empty or contain amorphous protein globules
- Epithelial cells occasionally form small scattered nests
- Abundant collagen separates and surrounds the tubular and acinar structures
- Brush border of elongated, thin microvilli
- Well-formed desmosomes associated with tonofibrils
ADDITIONAL DIAGNOSTIC TESTS:
- Immunohistochemistry: Cytokeratin positive
- In recent research, these lesions were positive for cytokeratins, vimentin, CD-30, calretinin, and WT-1 (Wilms’ tumor 1 suppressor gene) and negative for Factor VIII-related antigen and CEA; this immunohistochemical profile is consistent with mesothelial differentiation
- Entrapped mesothelium (during embryogenesis)
- Humans: One case report of a similar lesion in the ventricle of a patient undergoing bypass surgery; diagnosed as adenomatoid tumor. Adenomatoid tumors in man primarily occur in the urogenital tracts and are of mesothelial origin
- Rats: Usually affects older rats; proliferative; usually in the atrial free wall, but may extend into the interatrial and left atrial free walls; appear to be true neoplasms rather than ectopic rests of tissue
- Swine: Single report in fetal pigs with lesions in the ventricular wall and sinoatrial node; solid and vesicular patterns lined by columnar epithelium
- Alison RH, Elwell MR, Jokinen MP, Dittrich KL, Boorman GA. Morphology and classification of 96 primary cardiac neoplasms in Fischer 344 rats. Vet Pathol. 1987;24:488-494.
- Baker DC, Schmidt SP, Langheinrich KA, Cannon L, Smart RA. Bovine myocardial epithelial inclusions. Vet Pathol. 1992;30:82-88.
- Novilla MN, Sandusky GE, Hoover DM, Ray SE, Wightman KA. A retrospective survey of endocardial proliferative lesions in rats. Vet Pathol; 1991;28:156-165.
- Robinson WF, Robinson NA. The cardiovascular system. In: Maxie MG, ed Jubb, Kennedy, and Palmer’s Pathology of Domestic Animals. Vol 3. 6th ed. Philadelphia, PA: Elsevier; 2016:22.
- Tursi M, Martinetti M, Gili S, et al. Myocardial adenomatoid tumor in eight cattle: evidence for mesothelial origin of bovine myocardial epithelial inclusions. Vet Pathol. 2009; 46:897-903.