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Case Reports in Medicine
Volume 2012, Article ID 913517, 4 pages
Case Report

CD34 Expression in the Stromal Cells of Alveolar Adenoma

1Complex Operative Unit of Pathology, AORN Monaldi, Naples, 80131 Naples, Italy
2Complex Operative Unit of Thoracic Surgery, AORN Monaldi, Naples, Italy
3School of Medicine, Second University of Naples, Italy

Received 24 July 2012; Revised 19 September 2012; Accepted 20 September 2012

Academic Editor: Stephen P. Peters

Copyright © 2012 Nicolina De Rosa et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


The alveolar adenoma of the lung is a rare benign tumor characterized by a proliferation of both the alveolar epithelial cells and the mesenchymal septal cells. Immunohistochemically, the epithelial cells stain for cytokeratin (CK) AE1AE3, CK7, thyroid transcription factor 1 (TTF1), and surfactant apoprotein confirming the derivation by the type 2 pneumocytes. The stromal cells are negative for these markers but they show focally smooth muscle and muscle-specific actin positivity. We describe two cases that showed immunohistochemically a CD34 positivity of the mesenchymal septal cells. This aspect has been previously described in a two cases report, but not emphasized by the authors as a distinctive feature of the lesion. We consider this CD34 positivity as a marker of immaturity or stemness of the lesional septal spindle cells, that could be responsible of the different phenotypic and morphological profile of the interstitial cells, that could be, therefore, considered neoplastic and not reactive.