VILLIN, CYTOKERATIN-7, AND CYTOKERATIN-20 EXPRESSION IN PULMONARY ADENOCARCINOMA WITH ULTRASTRUCTURAL EVIDENCE OF MICROVILLI WITH ROOTLETS

Villin (V) is a glycoprotein of microvilli associated with rootlet for mation. Most colonic adenocarcinomas have a V positive (+), cytokerati n (CK) 20 (+), CK7-negative (-) immunophenotype; most lung adenocarcin omas have a CK20(-), CK7(+) immunophenotype. The reports of villin imm unoreactivity in lung adenocarcinoma range from 6% to 68% in studies u sing various fixations and varied anti-villin antibodies. Some lung ad enocarcinomas have microvilli with rootlets leading to possible diagno stic confusion with metastatic colonic adenocarcinoma to lung. Nine pr imary lung adenocarcinomas with rootlets on ultrastructure (including four bronchioloalveolar carcinomas [BAC]), four metastatic lung adenoc arcinomas with rootlets, nine metastatic colon adenocarcinomas to lung , and 10 randomly selected lung adenocarcinomas without rootlets (incl uding five BAG), were immunostained with monoclonal antibodies to vill in (1D2C3), CK7 (OV-TL12/30), and CK20 (Ks20.8) using a streptavidin p eroxidase technique with heat-induced epitope retrieval. All primary l ung adenocarcinomas with rootlets were CK7(+) CK20(-), and six of nine (67%) were V(+). Cytoplasmic villin positivity occurred in a diffuse- five of nine (56%), focal-two of nine (22%), or brush border pattern-t wo of nine (22%). Two of four metastatic lung adenocarcinomas with roo tlets were V(+). One metastatic lung adenocarcinoma had a CK7(+), CK20 (+), V(-) phenotype. GU metastatic colonic adenocarcinomas were V(+), CK20(+), CK7(-), and 1 of 10 (10%) lung adenocarcinomas without rootle ts was V(+), and all 10 were CK20(+), and CK7(+). In summary, villin p ositivity is more common in lung adenocarcinoma with rootlets (67%) th an those without rootlets (10%). All primary lung adenocarcinomas were CK7(+), CK20(-). The combination of villin, CK 7, and CK 20 is helpfu l in differentiating metastatic colon adenocarcinoma from lung adenoca rcinoma with rootlets. Copyright (C) 1998 by W.B. Saunders Company.