A 72-year-old woman comes to the office due to a persistent cough over the last 2 months that is occasionally associated with scant, white sputum. She has also lost 4.5 kg (10 lb) since the onset of her symptoms. The patient is an ex-smoker with a 25-pack-year history. She was diagnosed with mild chronic obstructive pulmonary disease several years ago, and she uses albuterol as needed for episodes of wheezing and shortness of breath. Physical examination shows scattered wheezes bilaterally. Chest CT scan reveals a mass in the right lung. Light microscopy of the mass is shown below: Which of the following is the most likely diagnosis?

Question

A 72-year-old woman comes to the office due to a persistent cough over the last 2 months that is occasionally associated with scant, white sputum.  She has also lost 4.5 kg (10 lb) since the onset of her symptoms.  The patient is an ex-smoker with a 25-pack-year history.  She was diagnosed with mild chronic obstructive pulmonary disease several years ago, and she uses albuterol as needed for episodes of wheezing and shortness of breath.  Physical examination shows scattered wheezes bilaterally.  Chest CT scan reveals a mass in the right lung.  Light microscopy of the mass is shown below:  Which of the following is the most likely diagnosis?

Quizplus · Accepted Answer

11ec160b_3a14_ddd9_9249_9f3d8daaa3b7_MD0001_00 This patient's histologic findings are consistent with adenocarcinoma of the lung, the most common type of primary lung cancer in the United States. It is also the most common type seen in nonsmokers, although like most forms of lung cancer, the risk is increased with prolonged smoking history. Adenocarcinoma arises from the alveolar epithelium and is characterized by invasive cells with abundant cytoplasm and eccentrically placed nuclei that form irregular glandular elements; mucin production is common. Clinical manifestations are similar to other types of lung cancer and include cough, dyspnea, hemoptysis, and unexplained weight loss. Mucinous forms can produce copious amounts of watery sputum (bronchorrhea). Imaging shows a discrete mass or pneumonia-like consolidation, typically located on the periphery of the lung. (Choice B) Mesothelioma is a rare malignancy associated with asbestos exposure; it arises from mesothelial cells and is located in the pleura (not the lung parenchyma, as in this patient). Histopathology demonstrates cuboidal or spindle cells that stain positive for cytokeratin. (Choice C) Pulmonary tuberculosis typically presents with a cavitary lesion in the upper lungs, often associated with hilar adenopathy. Histology demonstrates caseating granulomas with multinucleated giant cells. (Choice D) Small cell lung cancer is an aggressive malignancy strongly associated with smoking; it often arises in the major bronchi. Histopathology demonstrates small, blue cells with scant cytoplasm, indistinct nucleoli, and granular chromatin (salt and pepper pattern). (Choice E) Squamous cell lung cancer is associated with smoking and typically arises centrally within a bronchial lumen. Histopathology demonstrates invasive squamous cells with intercellular bridges and keratin pearls. Educational objective: Adenocarcinoma, the most common pulmonary malignancy, is characterized histopathologically by invasive glandular cells with abundant cytoplasm and eccentrically placed nuclei; mucin production is common. Imaging typically demonstrates a discrete mass or pneumonia-like consolidation at the periphery of the lung.

A 72-Year-Old Woman Comes to the Office Due to a Persistent