A 62-year-old woman with a 30-pack-year smoking history is evaluated.

A 62-year-old woman with a 30-pack-year smoking history is evaluated with a history of chronic shortness of breath. She has mild left-sided chest discomfort. She denies fever, chills, and night sweats and has no localizing signs on physical exam. A CT-guided needle biopsy of the lesion seen in the CXR in Fig. below is performed and reveals malignant cells.

Based on the CXR finding, the likely diagnosis is
a. Small cell carcinoma
b. Bronchoalveolar cell carcinoma
c. Adenocarcinoma of the lung
d. Liposarcoma of the chest wall

This malignancy is associated with
a. Positive sputum cytology
b. A good response to chemotherapy
c. Incidentally detected peripheral carcinomas on CXR
d. Cavitation in the majority of these carcinomas

Bilateral lower zone haziness is seen secondary to soft tissue shadows. An irregular 1.5 × 2-cm shadow is noted in the left middle lung zone peripherally abutting the left chest wall

The answers are 6-c, 7-c. An SPN in a 42-year-old smoker mandates a diagnostic workup. In this case, a CT-guided biopsy revealed malignant cells. Adenocarcinoma is commonly peripheral and represents about 30% of the total number of lung cancer cases. Its incidence is rising especially in females. Adenocarcinoma frequently presents as an incidental finding on x-ray. The other major histological types of lung cancer tend to have central localization and are as follows:

• Squamous (epidermoid) carcinoma. Eighty percent are central; when peripheral, they have a tendency for cavitation.
• Small cell (oat cell) carcinoma. Believed to originate from neuroendocrine cells of the bronchial mucosa, these are usually central with mediastinal involvement.
• Large cell undifferentiated carcinoma with mixed malignant features.
• Bronchoalveolar carcinoma. A variant of adenocarcinoma, these arise from type II pneumocytes in the alveoli. They may simulate pneumonia with focal consolidation or may present as solitary or multiple nodules.