A 76-year-old man has had worsening shortness of breath, cough, and weight loss for the past several months. He is a lifelong nonsmoker. Chest imaging reveals irregular pleural thickening. A surgical biopsy is planned, but the patient refuses, choosing to receive hospice care instead. He dies several weeks later. Autopsy examination is performed, and a photograph of the cut lung section is shown below. Histopathological examination of the abnormal tissue is most likely to reveal which of the following findings?

Question

A 76-year-old man has had worsening shortness of breath, cough, and weight loss for the past several months.  He is a lifelong nonsmoker.  Chest imaging reveals irregular pleural thickening.  A surgical biopsy is planned, but the patient refuses, choosing to receive hospice care instead.  He dies several weeks later.  Autopsy examination is performed, and a photograph of the cut lung section is shown below.  Histopathological examination of the abnormal tissue is most likely to reveal which of the following findings?

Quizplus · Accepted Answer

11ec160b_3b2d_5317_9249_b569e535df2a_MD0001_00 This nonsmoking patient with dyspnea, cough, and weight loss has pleural thickening on imaging; gross pathology of the lungs demonstrates an encasement of the lungs in a rind-like, calcified mass. This presentation is consistent with mesothelioma, a rare, malignant neoplasm arising from the mesothelial cells that line body cavities (eg, pleural, peritoneal, pericardial). In early mesothelioma, multiple nodules form on the parietal pleura and gradually grow to encase the lung parenchyma (which is typically uninvolved). Pleural effusions are common and frequently hemorrhagic. Mesotheliomas typically present with slowly progressive dyspnea, cough, chest pain, and weight loss. Asbestos exposure is the primary risk factor; individuals with occupational exposure (eg, mining, shipbuilding, insulation installation) are at increased risk. Histologically, mesothelioma can appear as cuboidal or flattened cells (epithelium-like) or spindle cells (stromal-like). Immunohistochemistry is an important diagnostic marker; nearly all cases of mesothelioma will stain positive for cytokeratins and many will also typically stain positive for calretinin. Electron microscopy usually shows polygonal tumor cells with numerous long, slender microvilli and abundant tonofilaments. (Choice A) Tuberculosis is characterized by caseating granulomas with giant cell formation; patients typically have hilar adenopathy and upper lobe infiltrates. Tuberculosis occurs most commonly in immunosuppressed patients or those at high exposure risk (eg, health care workers, incarcerated individuals). (Choice B) Silicosis is associated with inhaled silica (eg, mining, sand blasting); histology demonstrates nodules composed of whorled collagen fibers and dust-laden macrophages. Imaging demonstrates innumerable upper lobe-predominant nodes within the pulmonary parenchyma. (Choice C) Small cell lung cancer is characterized by small round cells; however, this malignancy typically arises in the central airways (not the pleura). Neuroendocrine markers, including chromogranin and synaptophysin, are typically positive. (Choice E) Empyema-composed of a thick, fibrinous exudate and pus-typically occurs when bacteria infect the pleural space (typically from an associated pneumonia). Patients often present with fever, chills, and (occasionally) sepsis, not months of weight loss and dyspnea. Educational objective: Mesothelioma is a neoplasm arising from mesothelial cells and is strongly associated with asbestos exposure. In early mesothelioma, multiple nodules form on the parietal pleura and gradually encase the lung parenchyma. Immunohistochemistry is important for diagnosis; nearly all mesotheliomas stain positive for cytokeratins and many also stain positive for calretinin.

A 76-Year-Old Man Has Had Worsening Shortness of Breath, Cough