Common Metastatic Sites of Lung Adenocarcinoma

Lung adenocarcinoma most commonly metastasizes to the lymph nodes, liver, adrenal glands, bone, brain, and pleura. 1

Primary Metastatic Sites

Lymph nodes: Metastasis to lymph nodes is common, though symptoms are typically absent unless there is very bulky adenopathy 1
Liver: Liver metastases often present with symptoms of weakness and weight loss, but liver function tests typically remain normal until advanced stages of involvement 1
Adrenal glands: These metastases are typically asymptomatic and rarely cause adrenal insufficiency; they must be distinguished from benign adrenal adenomas 1
Bone: Occurs in 6-25% of patients at presentation, with vertebral bodies being the most common site, though any bone may be involved 1, 2
Brain: The lung is the primary site of about 70% of cancers that initially present with symptomatic brain metastases 1, 3
Pleura: Often manifests as pleural effusion, which should always raise concern for malignancy 1

Patients with distant metastases often present with nonspecific systemic symptoms including anorexia, weight loss, and fatigue 1
These systemic symptoms are associated with worse prognosis even within the same cancer stage 1

Bone metastases: Present with pain, bony tenderness, and possibly elevated serum calcium or alkaline phosphatase 1
- While most bone metastases are osteolytic, sclerotic (osteoblastic) bone metastases can also occur, though they are rare 2
Brain metastases: May present with headache, nausea, vomiting, seizures, mental status changes, or may be asymptomatic 1
- Lung adenocarcinoma has a strong propensity to metastasize to the brain, causing significant morbidity and mortality 3
Liver metastases: Often accompanied by weakness and weight loss, but liver function tests typically remain normal until very advanced stages 1

Gastrointestinal tract: Though previously considered rare, autopsy studies suggest gastrointestinal metastases may occur in up to 11% of lung cancer cases, often asymptomatic 4
Soft tissues: Incidence rate approximately 0.75-9%, presenting as soft tissue masses 5
Ocular and paranasal structures: Rare metastases can occur to the eye (ocular bulbus) and maxillary sinus 6

For patients with systemic symptoms suggesting metastatic disease, biopsy of a metastatic site can efficiently establish both diagnosis and stage 1
CT imaging with IV contrast is the preferred modality for detecting metastases in the chest, abdomen, and pelvis 1
Brain MRI is recommended for suspected brain metastases, with contrast increasing specificity for detection, especially for leptomeningeal spread 1
PET/CT has higher sensitivity (92%) than bone scan (86%) for detecting bone metastases 1

The presence of metastatic disease significantly impacts prognosis and treatment planning 1
Identifying patients at high risk for specific metastatic patterns (such as brain metastases) could facilitate closer surveillance or justify preventive treatments 3
Unusual metastatic presentations should not be overlooked, as they may be more common than previously thought 4, 6