Immunohistochemical Detection of CD34, E-cadherin, Claudin-1, Glucose Transporter 1, Laminin, and Protein Gene Product 9.5 in 28 Canine and 8 Feline Meningiomas

The variation in histologic pattern of meningiomas can make their diagnosis challenging. The immunohistochemical profile of 28 canine and 8 feline meningiomas was examined. Tumor types included anaplastic (6 dogs), angiomatoid (1 cat), fibroblastic (3 dogs, 1 cat), meningothelial (1 dog), microcystic (2 dogs), myxoid (3 dogs), psammomatous (4 cats), and transitional (13 dogs, 2 cats). The authors compared the expression of novel markers (CD34, E-cadherin, claudin-1, glucose transporter 1 [GLUT-1], laminin, and protein gene product [PGP] 9.5) with published markers (cytokeratins, glial fibrillary acidic protein [GFAP], progesterone receptor, S100, and vimentin). Neoplastic cells were immunohistochemically positive for vimentin in 100% of the meningiomas; CD34, 94%; GLUT-1, 86%; E-cadherin, 81%; S100, 75%; laminin, 72%; claudin-1, 60%; PGP 9.5, 55%; progesterone receptor, 44%; pancytokeratins, 39%; cytokeratins 8/18, 17%, and GFAP in 9%. Ki67 index did not correlate well with mitotic index. Based on these results and those in the human literature, immunohistochemistry for vimentin, CD34, and E-cadherin is proposed to support a diagnosis of meningioma. Immunohistochemistry for claudin-1, albeit of only moderate to low sensitivity in canine and feline meningiomas, may help to distinguish meningioma from some mesenchymal neoplasms involving the brain and associated structures, such as schwannomas, which in humans express claudin-1 poorly or not at all. Further studies with CD34, E-cadherin, and claudin-1 in canine and feline tumors that may mimic meningiomas are needed to determine the adequacy of this approach.