NONSPECIFIC FLUORESCENT WHITENER STAINS IN THE RAPID RECOGNITION OF PULMONARY DIROFILARIASIS - A REPORT OF 20 CASES

Background - Solitary lung nodules in humans caused by the dog parasit e Dirofilaria immitis are steadily increasing in number. The organisms can be easily missed in haematoxylin and eosin stained tissue when th ey are degenerated and pale staining, Methods - The value of Tinopal C BS-X (TCBS-X) and Calcofluor white (CFW), two rapid, inexpensive, simp le nonspecific fluorescent whitening stains, were assessed in the iden tification of these worms. Deparaffinised rehydrated tissue slides pre pared from the pulmonary nodules were stained for one minute in 1% w/v aqueous solutions of TCBS-X or CFW, counterstained, coverslipped, and viewed with a fluorescent microscope. Results - The stains demonstrat ed the intact worm and worm fragments in 20 cases of pulmonary dirofil ariasis collected from hospitals in Houston. The filariae and fragment s of filariae stained bright green while the background tissue stained red, delineating the internal structures of the worm. Conclusions - D irofilariasis should be included in the differential diagnosis of subp leural masses, and non-specific fluorescent whitening stains can help in the rapid recognition of the fragmented organism in cytological or surgical material.