"Tail" signs associated with pulmonary lesions: critical reappraisal

Recent experience at The University of Texas M. D. Anderson Hospital has cast doubt on the specificity of the pleuropulmonary "tail" signs and on their ability to differentiate malignant from benign pulmonary lesions. To critically reappraise their usefulness, a three part study was undertaken: (1) a prospective collection of data on 45 consecutive patients whose chest radiographs demonstrated a tail sign; (2) a retrospective review of radiographs of 121 patients with bronchioloalveolar carcinoma, in which tail signs are reportedly frequent; and (3) a retrospective review of radiographs of 72 patients with proven tuberculous lesions. Pleuropulmonary tail signs were considered of three types: a thin line (tail sign); one or more thickened lines ("rabbit ears" sign), or a tapered line ("participating tail" sign) extending from a lesion to the pleural. The results demonstrate that these signs are nonspecific features of peripherally located pulmonary lesions and, if used to differentiate a malignant from a nonmalignant lesion, may lead to serious diagnostic errors. On the other hand, a transition from one type of sign to another is useful in evaluating activity. A tail sign may call attention to an otherwise obscure lesion.