Myocardial Adenomatoid Tumor in Eight Cattle: Evidence for Mesothelial Origin of Bovine Myocardial Epithelial Inclusions

Abstract

The adenomatoid tumor is an uncommon benign lesion, thus far described only in humans. Adenomatoid tumors typically arise in the genital tract, exceptionally in the heart, and usually represent an incidental finding. Microscopically, they are constituted by epithelioid cells that form tubular structures and anastomosing channels within a fibrous stroma. Mesothelial origin of these lesions is suggested by their immunohistochemical characteristics. In cattle, previously reported myocardial epithelial inclusions are morphologically similar in that the cells are immunoreactive for both cytokeratins and vimentin, and bear surface microvilli. Myocardial lesions found incidentally at slaughter in 8 cattle histologically resembled the so-called bovine myocardial epithelial inclusions and had morphologic and immunohistochemical features consistent with human adenomatoid tumor. All lesions were in the left ventricular myocardium, adjacent to the epicardium, and composed of epithelioid cells that formed cords and tubules, and were immunoreactive for pan-cytokeratins, cytokeratin 5/6, vimentin, calretinin, Wilms' tumor 1 suppressor gene, and CD30 antigen. By electron microscopy, numerous long slender microvilli were associated with desmosomes and tonofibrils. The immunohistochemical and ultrastructural features were considered consistent with mesothelial origin. These lesions, corresponding to the previously described myocardial epithelial inclusions in cattle, might be considered embryologic rests and could represent the bovine counterpart of the human adenomatoid tumor.

Sudden death of a crossbred calf associated with a myocardial adenomatoid tumour

“…The mass identified in this calf appeared on routine histopathology to be the same as those described as adenomatoid tumours in a series of cattle from Italy, identified as incidental lesions in animals at slaughter. The immunohistochemical staining results in the present case were consistent with a tumour of bimorphic mesothelial origin, as previously described.…”

“…von Willebrand’s factor and desmin stains were negative, although the internal controls of the vascular elements in the mass and adjacent myocardium stained appropriately. Based on these staining characteristics, a tumour of mesothelial cell origin was considered most likely and a search of the literature identified a publication from Italy where masses described as adenomatoid tumours had been found rarely in cattle hearts at slaughter . Therefore, immunostaining for additional markers of mesothelial cells was attempted, based in part on those used in the published study, but some immunoreagents were not available and others, including calretinin and CK5/6, have not been validated for use in cattle and internal controls were not positive.…”

A Comparative Review of Canine and Human Rhabdomyosarcoma With Emphasis on Classification and Pathogenesis

“…These have been termed myocardial epithelial inclusions or myocardial adenomatoid tumors. 12,135,152 They are hamartomas composed of pericardial mesothelial inclusions. Poorly differentiated sarcomas are occasionally reported in the literature.…”

Cardiac Angioleiomyoma in 44 Cattle in Japan (1982–2009)

“…A wider range of primary cardiac tumors has been reported in cattle than in any other animal. Examples include rhabdomyoma, 20,21,29 rhabdomyosarcoma, 19,24,29,34 peripheral nerve sheath tumors (neurofibroma, schwannoma, neurinoma, neurofibroma), 11,18,20,22 –24,26,29,31 hemangioma, 22,29,37 hemangiosarcoma, 6,29 fibroma, 18 fibrosarcoma, 18,29,33 angiolipoma, 8 leiomyoma, 29,33 leiomyosarcoma, 29 adenomatoid tumor, 35 hamartoma, 29 mesothelioma, 29,32 and myxoma. 3,20…”