[1902] Intrapulmonary Mesothelioma Simulating Interstitial Lung Disease: A Distinctive Variant of Mesothelioma. Report of 5 Cases and Review of the Literature

Brandon T Larsen, Julianne RH Klein, Helena Hornychova, Rathna Nuti, Seshadri Thirumala, Kevin O Leslie, Thomas V Colby, Henry D Tazelaar. Mayo Clinic, Rochester, MN; University of Manitoba, Winnipeg, MB, Canada; Charles University Prague, Hradec Kralove, Czech Republic; Texas Tech University Health Science Center, Lubbock, TX; AmeriPath, Lubbock, TX; Mayo Clinic, Scottsdale, AZ

Background: Mesothelioma is an uncommon thoracic malignancy that typically encases lungs and mediastinal structures in a thick rind, while relatively sparing lung parenchyma. We describe an unusual presentation of mesothelioma characterized by diffuse intrapulmonary growth, without significant pleural involvement, clinically simulating interstitial lung disease.
Design: We identified 5 patients (median age 56 yrs, all men) with intrapulmonary mesothelioma in our pathology consultation practices from 2010-2012. Clinical history, imaging, and pathology materials were reviewed.
Results: Clinical symptoms included chronic shortness of breath with or without cough (4 cases) and acute shortness of breath with bilateral pneumothorax (1). Chest imaging showed diffuse ground glass opacities in all cases, as well as reticular abnormalities (2), small pleural effusions (2), and scattered small nodular densities (1). Pleural plaques, thickening, or masses were not seen. A presumptive clinicoradiologic diagnosis of interstitial lung disease was made in all cases, and wedge biopsies were performed. Histologic evaluation revealed plump epithelioid or bland spindled cells with various growth patterns, including areas of alveolar filling by tumor cells mimicking desquamative interstitial pneumonia (DIP), nodular hyalinized fibrosis mimicking pneumoconiosis, lepidic growth mimicking reactive pneumocytes or adenocarcinoma in situ, and tubulopapillary and micropapillary patterns mimicking invasive adenocarcinoma. Initial diagnoses by referring pathologists included DIP (1), hypersensitivity pneumonitis (1), reactive changes (1), and mesothelioma (2). Consultative review revealed focal microscopic pleural involvement in 4 cases. Additional immunohistochemistry showed at least 3 positive mesothelial markers and at least 3 negative adenocarcinoma markers in all cases, consistent with mesothelioma. Median survival with and without chemotherapy was 28 months (3) and 3.5 weeks (2), respectively.
Conclusions: “Diffuse parenchymal pulmonary mesothelioma” is a rare and distinctive presentation that clinically mimics interstitial lung disease. Recognition of this occurrence is essential to avoid misdiagnosis.
Category: Pulmonary

Tuesday, March 5, 2013 1:00 PM

Proffered Papers: Section D, Tuesday Afternoon

 

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