Dr. Pepe’s Diploma Casebook: CASE 130 – SOLVED

Findings: PA radiograph depicts an ill-defined opacity in the RUL (A, arrow). Lateral view shows a well-defined ovoid opacity (B, arrow), interpreted as loculated fluid in the major fissure.

The patient returned four months later with pain in the chest and back. Bone scan discovered numerous metastases (C, red arrows). Enhanced axial CT demonstrated an irregular mass in the RUL (D, arrow). Needle biopsy confirmed the diagnosis of carcinoma.

Final diagnosis: carcinoma of the lung simulating loculated fluid in the major fissure

In the previous Diploma, I presented carcinoma cases missed because they were partially hidden. In today’s presentation I will discuss another cause: failure of recognition, which can be due to malignancy simulating a benign condition or malignancy associated with benign manifestations.

Among the various appearances that lead to failure of recognition I have chosen the ones I am most familiar with. They include:

* carcinoma simulating loculated fluid in the fissure,
* carcinoma presenting as a thin-walled cavity,
* malignancy associated with bullous disease, and
* carcinoma presenting as acute pulmonary infarction.

Carcinoma simulating loculated pleural fluid in a fissure is uncommon. Over the years I have collected several cases, one of which I am showing below (Fig. 1). As lung carcinomas usually respect the fissures, my humble opinion is that this appearance is due to the tumor bulging the fissure without invading it.

Fig. 1. 70-year-old man with chest pain. PA chest film shows a rounded opacity at the right lung base (A, arrow). Because of the appearance in the lateral view, it was initially interpreted as loculated fluid in the major fissure (B, arrow). Unenhanced axial CT taken a few days later shows a solid mass in the RML (insert, arrow). Surgical diagnosis: carcinoma
 

Carcinoma presenting as a single thin-walled cavity occasionally occurs. This appearance is usually confused with a benign condition and the diagnosis is delayed. It may be associated with a pre-existing cavity (Fig. 2) or develop as an insufflated malignancy by a check-valve mechanism (Fig. 3).

Fig. 2. 72-year-old man with a stable thin-walled cavity in the LLL (A, arrow). A year later the cavity has increased in size, still with a thin wall (B, arrow). Control study the next year depicts decreased size and thickening of the posterior wall (C, arrow). PET-CT shows uptake in the posterior wall (D, arrow). Malignancy was suspected. The patient refused surgery and percutaneous biopsy, and it was decided to do a follow-up study.

Three months later enhanced axial CT shows that the cystic cavity has disappeared and in its place, a solid mass has developed (E and F, arrows) with increased overall uptake on PET-CT (G, arrow). At surgery, an adenocarcinoma was found.

Fig. 3. 63-year-old woman with acute chest pain and dyspnea. PA radiograph shows an obvious pneumothorax with a cavity in the RUL (A, arrow). After chest tube placement, the pneumothorax has resolved and a thin-walled cavity is visible in the right upper lobe (B, arrow). It was interpreted as a congenital cyst, and follow-up radiographs were requested

PA radiograph two months later shows a large thick-walled cavity in the RUL (C, arrow). Axial CT confirmed the thick-walled mass and involvement of the whole RUL. The most revealing finding is a narrowing of the proximal RUL bronchus (D, circle), with a thick rim of tissue around it, highly suspicious of a central mass. PET-CT confirmed high uptake at the proximal RUL bronchus, as well as the periphery of the cavity (E, arrows). Bronchoscopy confirmed adenocarcinoma. Diagnosis: central carcinoma with probable check-valve cavity and seeding within the cavity.

Patients with bullous disease are at a higher risk than the general population of developing lung carcinoma (Fig. 4). They are also prone to infection, which should not be confused with malignancy. Rapid progression and improvement of the changes favors the diagnosis of an infectious condition (Fig. 5).

Fig. 4. 45-year-old man with apical bullae (A), presenting with hemoptysis and an RUL opacity (B, arrow). 

Axial CT shows a large opacity (C, arrow) occupying the bullous area in the RUL (D, arrow).
Adenocarcinoma was proven at surgery.

Fig. 5. 66-year-old man with bullous disease (A) who presented with cough and fever. PA radiograph shows RUL opacification and loss of volume (B, circle). Three weeks after treatment the changes have improved (C, circle). 

Initial CT images show opacities (D and E, arrows) that cannot be differentiated from neoplasia. Final diagnosis: infected bullae. Compare with Fig. 4.

Sometimes, the benign manifestations accompanying lung malignancy overshadow the carcinoma. This is the case of pulmonary embolism, which is a common companion of lung malignancy. The neoplasm is usually found when CT is done to study the embolism (Figs. 6 and 7).

Fig. 6. 55-year-old man consulting for acute chest pain. PA film shows two Hampton humps in the right lower lung (A, white arrows). The left hilum is abnormal (A, red arrow). Enhanced coronal CT confirms the infarcts (B, white arrows), as well as a pulmonary mass (B, red arrow) and lymphadenopathy in the aorto-pulmonary window (B, yellow arrow). Findings were overlooked in a radiograph taken seven months earlier (C, yellow and red arrows). Proven bronchogenic carcinoma.
 

Fig. 7. 58-year-old woman with acute chest pain. Chest radiographs (A and B) show a Hampton hump at the right costophrenic angle (A, white arrow). A mass in the lower right hilum was overlooked (A, red arrow). 

Enhanced sagittal CT confirms the infarct (C, arrow). Axial shows the RLL mass (D, arrow) which enhanced after contrast injection (E, arrow). Final diagnosis: adenocarcinoma of the lung

Very rarely, lung carcinoma may undergo a spontaneous decrease in size, which results in the erroneous diagnosis of benign disease. I have seen two such cases during my professional life (Fig. 8). The cause is unknown and may be related to the patient’s immunologic state.

Fig. 8. 72-year-old man with hemoptysis. Lateral film shows an ovoid opacity in the LUL (A, arrow).
Nine weeks later the opacity has decreased in size (B, arrow). A new radiograph (not shown) depicted a new increase in size. Axial CT at that time confirmed a mass in the LUL (insert, arrow). Carcinoma proven at surgery. 

Follow Dr. Pepe’s advice:

1. Failure of recognition occurs when a carcinoma simulates benign disease.

2. Beware of thin-walled cavities and neoplasms occurring in bullous diseases.

3. Pulmonary embolism may herald the presence of an unsuspected carcinoma