[Histopathologic findings for the research of acid-fast bacilli in erythema nodosum].
It was possible to prove, by means of retrospective histopathological studies of 51 glass slides of common erythema nodosum (EN) and 39 glass slides of erythema nodosum leprosum (ENL), that the histopathological features of the two groups differed in several ways. It was found that the most prominent divergent findings between these two diseases was the presence of a lepromatous granulomatous infiltrate in the ENL; the predominant location of the inflammatory infiltrate was derma-hypodermal in ENL and hypodermal in common EN; there was a preferential septa attack in common EN and lobular in ENL; foreign giant cells occurred only in common EN; the lymphocyte cell infiltration in common EN and of neutrophils in ENL and the presence of inflammatory infiltrate around nerves in ENL. Our study has proved that the search for M. leprae does not have to be made in all cases of EN as there are histological differences in the routine histopathological exam between common EN and ENL that can alert to the real need for this procedure. This search must be performed when during the routine histopathological exam of sections stained by hematoxilin-eosin the ENL histopathological characteristics delineated herein are observed.