Makindo Medical Notes

Cannonball metastases refer to large, round, well-defined pulmonary metastases, typically seen on chest radiographs or CT scans. They are named "cannonball" because of their spherical appearance, which resembles cannonballs. These lesions are most often associated with hematogenous spread of malignancies to the lungs.

Common Primary Cancers Associated with Cannonball Metastases

• Renal Cell Carcinoma (RCC): One of the most common causes of cannonball metastases, particularly when the primary tumour has gone undiagnosed for a period of time.
• Choriocarcinoma: A rare but aggressive tumour often seen in young women, choriocarcinoma can rapidly spread to the lungs, producing cannonball lesions.
• Testicular Cancer: Non-seminomatous germ cell tumours (NSGCT) often present with lung metastases in the form of cannonball lesions.
• Prostate Cancer: Though rare, prostate cancer can metastasize to the lungs in an advanced stage, occasionally manifesting as cannonball metastases.
• Breast Cancer: Another potential primary malignancy that can lead to the development of pulmonary metastases resembling cannonballs, although less common than other cancers.
• Soft Tissue Sarcomas: Sarcomas may also present with large, round pulmonary metastases.
• Colon Cancer: In rare cases, colon cancer can present with pulmonary metastases of this appearance.

Appearance

Clinical Presentation

• Asymptomatic: Many patients may be asymptomatic, especially when lesions are detected incidentally on imaging.
• Cough: A persistent cough can develop if the metastases become large enough to irritate the lungs or airways.
• Dyspnea: Shortness of breath may occur as the lesions grow or as lung function becomes impaired.
• Hemoptysis: Rare but possible if the tumour invades blood vessels within the lungs.
• Constitutional Symptoms: Fever, weight loss, and fatigue may occur due to the underlying malignancy.

Radiological Appearance

• Chest X-ray: Cannonball metastases appear as multiple, well-circumscribed, round opacities distributed throughout both lung fields. The lesions vary in size but are typically large, resembling "cannonballs."
• CT Scan: Provides more detailed images, allowing better visualization of the size, number, and distribution of the metastases. CT also helps assess any pleural involvement or lymph node metastasis.
• Pattern: Typically bilateral and spread throughout the lungs, without a specific predilection for any part of the lungs.

Differential Diagnosis

The differential diagnosis for multiple pulmonary nodules, including cannonball metastases, includes:

• Primary Lung Cancer: Although typically more irregular in shape, multiple metastases from a primary lung tumour should be considered.
• Granulomatous Disease: Tuberculosis (TB), fungal infections, and sarcoidosis may present with multiple pulmonary nodules.
• Rheumatoid Nodules: Can appear as multiple pulmonary nodules in patients with rheumatoid arthritis.
• Wegener’s Granulomatosis: Can cause multiple nodules or masses in the lungs.
• Septic Emboli: In the setting of endocarditis or infected central lines, septic emboli can cause multiple lung lesions that resemble metastases.

Diagnostic Workup

• Imaging:
  • Chest X-ray is often the first imaging modality that identifies cannonball lesions.
  • CT scan is essential for further characterization of the nodules, assessment of other thoracic structures, and evaluation of potential metastases in other regions.
• Biopsy: A biopsy of one of the nodules, if accessible, can confirm the diagnosis of metastatic disease and identify the primary tumour if it is not already known.
• Tumor Markers: Elevated tumour markers, such as beta-hCG in choriocarcinoma or AFP in testicular cancer, can help pinpoint the primary malignancy.
• Further Investigation: Staging workup to identify the primary tumour if unknown, including abdominal or pelvic imaging, and possibly PET-CT scans.

Management

• Treatment depends on the primary cancer:
  • Renal Cell Carcinoma: May be managed with targeted therapy (e.g., tyrosine kinase inhibitors, immunotherapy) or surgery.
  • Choriocarcinoma: Highly responsive to chemotherapy (e.g., methotrexate or combination regimens).
  • Testicular Cancer: Typically treated with a combination of chemotherapy (e.g., BEP regimen) and surgery if necessary.
  • Breast Cancer: Management may include a combination of chemotherapy, hormone therapy, and targeted therapies.
• Surgical Resection: In rare cases, surgical resection of the metastases may be considered, particularly if they are solitary or limited in number and the primary tumour is controlled.
• Palliative Care: For patients with advanced metastatic disease, palliative care aimed at symptom management (e.g., relieving dyspnea, managing pain) is an essential part of the treatment plan.

Prognosis

The prognosis of cannonball metastases is generally poor, as the presence of multiple large pulmonary metastases indicates advanced-stage cancer. However, the prognosis largely depends on the primary cancer type, its response to treatment, and the extent of metastatic spread. For example, testicular cancer with cannonball metastases has a better prognosis than most other cancers, given its high response rate to chemotherapy.