Neuroectodermal marker proteins in normal myxoid tissue and cartilage

M Egerbacher, DVM PhD, P. Boeck, MD PhD

Institute of Histology and Embryology, University of Veterinary Medicine Vienna, Veterinaerplatz 1, A-1210 Vienna, Austria

AIM Myxoid connective tissue is well known in diagnostic pathology: it constitutes or contributes to benign and malignant tumors and stroma of tumors may show myxoid transformation. We observed areas of myxoid tissue also in normal connective tissue, e.g. in the human larynx, epiglottic cartilage of carnivores, cat lingual papillae, papillae of the ruminant omasum, and in digital pads of horses. METHODS Immunostaining was performed on sections from formalin fixed (4%) paraffin-embedded specimens. Unlabeled primary antibodies were detected with DakoEnVision® secondary Ab system and subsequent peroxidase reaction. RESULTS Myxoid areas were characterized by abundant alcianophilic, hyaluronidase sensitive matrix, indicating hyaluronan as its major constituent. Myxoid tissue often showed close spatial relationship to unilocular fat and/ or cartilage (fibrous, elastic, hyaline). Vascular supply was inconspicuous. Myxoid cells were ramified, stellate or spindle-shaped, and stained for vimentin like fibrocytes. Myxoid cells also expressed S-100 protein, GFAP, and occasionally NSE, which are generally accepted markers for neuroectodermal cells. Moreover, also fat cells (S-100) and chondrocytes (S-100, GFAP, NSE) expressed neuroectodermal marker proteins. CONCLUSIONS Simultaneous expression of vimentin and neuroectodermal marker proteins not necessarily indicates pathological changes or neuroectodermal origin of the respective cells; this should be considered when using the markers for diagnostic purpose. Location in the body and function of the tissue specimens studied suggest that mechanical stress on normal connective tissue cells elicits expression of neuroectodermal marker proteins.

KEY WORDS: connective tissue.

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Paper presented at the International Symposium on Predictive Oncology and Intervention Strategies; Paris, France; February 9 - 12, 2002; in the section on Diagnostic Markers.