Differential Diagnosis of Metastatic Lesions in the Lung

Abstract

Focal lung lesions may consist of tumor-like conditions,primary benign tumors, primary malignant tumors or tumor metastases. Tumor-like conditions that may mimic primary lung cancer or metastatic cancer in the lung not only radiologically but also histologically are reactive lesions like plasma cell granuloma, sugar tumor, sclerosing hemangioma, and hamartomas (1). A single focal lesion in the lung is more likely to be primary than secondary lung cancer (2). However, a solitary lung metastasis may be seen in patients with primary tumors of the breast, uterus, testis, colon, kidney and urinary bladder, and in malignant melanoma (2). The carcinomas with the highest propensity to produce metastatic lung disease are those arising in the lung, the breast, the gastrointestinal tract, and the genitourinary system (2). Discrete hematogenous metastatic lung nodules may be found in malignant melanomas, bone sarcomas, trophoblastic tumors and renal cell and thyroid carcinoma (2). Diffuse interstitial and lymphangitic infiltration is found in tumors of the liver, pancreas, stomach, and breast (2). Cytological or histological diagnosis can be obtained by bronchoscopy, bronchial brushing, mediastinoscopy, percutaneous needle aspiration, and percutaneous trephine lung biopsy (2). In the following paragraphs principles and practice of pathological diagnosis of metastatic tumors will be discussed and relevant examples will be given.