Lung Carcinoma Masquerading as Desquamative Interstitial Pneumonia (DIP): Report of 7 Cases and Review of Literature
Kirtee Raparia, James Ketterer, Mercedes L Dalurzo, Yu-Hui Chang, Thomas V Colby, Kevin O Leslie. Northwestern University Feinberg School of Medicine, Chicago, IL; Italian Hospital of Buenos Aires, Buenos Aires, Argentina; Mayo Clinic, Scottsdale, AZ
Background: Malignant tumors in the lung (both primary and metastatic) may rarely be associated with marked discohesion of tumor cells, with extension into the alveolar spaces in a pattern reminiscent of “desquamative interstitial pneumonia” (DIP). A peculiar aspect of this growth pattern is the relatively bland appearance of the tumor cells, in many cases simulating histiocytes, potentially a pitfall in the diagnosis.
Design: We searched the Charles Carrington Memorial consultation files in the Mayo Clinic Arizona Pathology Department for instances of malignant tumors in lung simulating DIP, from 1992 to 2011. We identified 7 cases involving the transbronchial biopsies, needle core samples and resected lung specimens. Clinical, histopathological and immunohistochemical analysis of these 7 patients was performed, including detailed morphometric analysis of the individual tumor cells using calibrated measurement tools on digital images. We compared the results to a control group of 4 patients with DIP-reactions in smoking-related disease.
Results: 5 males and 2 females, 48 to 86 years in age (mean: 67.8 years) comprised the study group. The radiologic findings included lobar consolidation, ground glass opacities, and rarely nodule formation. Microscopically, the lung parenchyma was dominated by prominent individual tumor cells within the alveolar spaces. 4 had primary lung carcinoma (adenocarcinoma), while 3 had metastasis from other sites. Immunostains were performed on 6 out of 7 cases to make the diagnosis. Nuclear diameter, cytoplasmic size and nuclear/cytoplasmic (N/C) ratios in patient and control groups were compared using the Wilcoxon Rank-sum test. No significant difference in the diameters of nuclear and cytoplasm between cases and control groups (p=0.3447 and p=0.7055, respectively) was seen, and only a marginal significant difference in N/C ratios (p=0.0890) was seen. A more complex analysis, Generalized Estimating Equation analysis, showed a significant difference in N/C ratio between the two groups (p=0.0278).
Conclusions: A “DIP-growth pattern” of malignant tumors in lung is presented. Although the N/C ratio difference approached statistical difference, the key to diagnosis is the individual cytology of the tumor cells. Immunohistochemical studies (keratin or other markers) are essential to make an accurate diagnosis in these tumors.
Tuesday, March 5, 2013 1:00 PM
Poster Session IV # 294, Tuesday Afternoon