¹Department of Pathology, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA

Correspondence: Dr SA Yousem, MD, Department of Pathology – A610, UPMC – Presbyterian, 200 Lothrop Street, Pittsburgh, PA 15213-2582, USA. E-mail: yousemsa@upmc.edu

Received 5 October 2004; Revised 18 November 2004; Accepted 19 November 2004; Published online 17 December 2004.

Abstract

Six cases of an unusual variant of primary pulmonary adenocarcinoma resembling colorectal and sinonasal adenocarcinoma are presented. Pulmonary intestinal-type adenocarcinoma occurs in elderly Caucasians and is associated with a histology characteristic of colorectal/enteric adenocarcinoma: a garland-like architecture with a 'gland in gland' periphery, central 'dirty' necrosis, and elongated stratified columnar cells, lacking significant goblet or signet ring differentiation. While a resemblance to intestinal adenocarcinoma by light microscopy is present, immunohistochemical studies comparing these carcinomas with metastatic colorectal adenocarcinoma clearly show a respiratory phenotype with the neoplastic cells expressing thyroid transcription factor-1 and cytokeratin 7 to the exclusion of cytokeratin 20, and failing to express CDX-2. Stains for a variety of epithelial mucins (MUC1, MUC2, MUC5AC) also support this observation. The differential diagnosis with other pulmonary adenocarcinomas, especially those with mucinous differentiation, is discussed.