Pathologic changes after interstitial laser therapy of infiltrating breastcarcinoma

Background: Interstitial laser therapy (ILT) is a technique of destroying t umor cells via thermal energy. Prior studies have shown that the procedure is safe and efficacious in laboratory animals and that complete cell death, as assessed by tetrazollium staining, is achieved in the laser treated are a. Design: Forty women with localized, mammographically detectable, Tl breast cancers consented to be treated with ILT and then have the treated area sub sequently excised. The delay period ranged from 5 to 42 days. Prior to ILT, the diagnosis of breast carcinoma was established by stereotactic needle c ore biopsy. Results: All 40 cases showed a characteristic gross appearance, which consi sted of a series of concentric rings surrounding a cavity corresponding to the laser needle tip. The tissue immediately adjacent to the cavity appeare d coagulated and showed the same "wind-swept" nuclei seen with cautery arti fact. Surrounding this was a white-tan ring that histologically showed reco gnizable tumor. No necrosis, increased apoptosis or inflammatory infiltrate was noted in this area on hematoxylin-eosin sections. Immunostains for cyt okeratin were negative in the recognizable tumor cells despite intense stai ning in the epithelial cells outside the laser treated area. A ring of red tan tissue which histologic ally consisted of necrotic tumor was seen next and this, in turn, was surrounded by a rim of vascular proliferation and fa t necrosis. The breast tissue outside the zone of fat necrosis appeared to be unaffected by the laser therapy. Conclusions: ILT appears to be an effective way to treat small localized br east cancer. It is important for the pathologist to recognize the chances s een after ILT, especially the zone containing pseudoviable tumor. Cytokerat in may be a marker to identify these likely non-viable but recognizable tum or cells. The extent of the laser affected area is defined by vascular prol iferation and fat necrosis. (C) 2001 Excerpta Medica, Inc. All rights reser ved.