JSFiddle - React, Tailwind, and code Playground

HTML

<table>
    <tr>
        <TD class=xl76 style="BORDER-TOP: windowtext 0.5pt solid; HEIGHT: 15pt; BORDER-RIGHT: windowtext 0.5pt solid; WIDTH: 883pt; BORDER-BOTTOM: windowtext 0.5pt solid; BORDER-LEFT: windowtext 0.5pt solid; BACKGROUND-COLOR: transparent" height=20 width=1177
        colSpan=25>
            <FONT face=Calibri><STRONG>INDICADORES DO MÊS DE ABRIL DE 2016</STRONG></FONT>
        </TD>
    </tr>
</table>

JavaScript

var keepStyles = (function() {
    function getStyles(el) {
        var attr = el.getAttribute('style');
        return attr.split(';').map(function(chunk) {
            var rule = chunk.split(':').map(function(part) {
                return part.trim().toLowerCase();
            });
            return {
                type: rule[0],
                value: rule[1]
            };
        });
    }

    function setStyles(el,styles) {
        var string = styles.reduce(function(str, obj) {
            return str + [obj.type, obj.value].join(':') + ';';
        }, '');
        el.setAttribute('style', string);
    }
    return function(toKeep, el) {
        var current = getStyles(el);
        var keep = current.filter(function(obj) {
            return toKeep.indexOf(obj.type) != -1;
        });
        setStyles(el, keep);
    }
})();

keepStyles(['border-top'], document.querySelector('td'));