The spread of breast cancer: importance of the intrathoracic lymphatic route and its relevance to treatment

Abstract

Summary. Detailed necropsies were performed on 26 individuals who had died of disseminated breast carcinoma, to assess the frequency of spread to the lungs, pleura and pericardium, and to determine the likely routes of spread to these sites. Tumour was present in the lung parenchyma in 67% of the lungs examined, in the visceral pleura in 75%o and the parietal pleura in 5Oo0. Although even small deposits of pleural tumour were invariably visible to naked-eye examination, lung parenchymal involvement was almost invariably microscopic, despite its frequently extensive distribution. This finding draws attention to the difficulties of clinical staging with respect to lung metastases. Tumour in lymphatics predominated over that in blood vessels in both lung and pleura and this, together with the widespread mediastinal lymphnode infiltration found, suggests that the lymphatic system forms the dominant route of spread of breast carcinoma to the thorax. The possible role of mediastinal lymphatics in the dissemination of breast cancer to bone and liver is also discussed. Our findings suggest that the fields of adjuvant irradiation after primary surgery should include the mediastinal lymphatic network.IT IS COMMONLY BELIEVED that the spread of breast cancer beyond the regional lymph nodes is haematogenous. However, the distinct clinical pattern of laterality of pleural effusions in breast cancer suggests a non-haematogenous mechanism of dissemination. When a pleural effusion develops for the first time in patients with unilateral breast cancer, it is usually on the same side as the primary breast lesion (Stoll & Ellis, 1953; Porter, 1965). This pattern of spread would be better explained by a regional mechanism of dissemination, because haematogenous tumour spread should involve both sides of the thorax synchronously and with equal frequency.Our previous necropsy experience had shown that disease within lymphatics was common at sites remote from the breast, especially in lung and pleura. We were also aware that visceral pleural disease was invariably macroscopic, whilst lung parenchymal disease was almost invariably microscopic. These observations prompted us to investigate the incidence of pulmonary and pleural metastases in breast cancer, to determine the extent of involvement of various mediastinal lymphnode groups, and to compare the frequency of intralymphatic and intravascular (blood) tumour. In this way further information on the mechanism of spread of breast cancer to the thorax might be obtained.

A study of immunohistochemical differential expression in pulmonary and mammary carcinomas

“…16,17 Autopsy studies on breast cancers reported metastasis to the lung in 57-77% of cases. 14,15,18,19 A variety of thoracic metastasis patterns of breast cancers are recognized, 20 including pleural metastasis, mediastinal tumor, lymphangitic carcinoma, multiple pulmonary nodules, solitary pulmonary nodule, endobronchial metastasis, and pulmonary tumor emboli. 20 Among these metastatic patterns, a solitary lung metastatic nodule would likely mimic a primary lung cancer, and, therefore, may cause a significant diagnostic challenge.…”

Breast lymphatic drainage via the pulmonary lymphatic system

“…Given that breast cancer is one of the known extrathoracic malignancies that metastasise to mediastinal nodes [3][4][5], this finding of a direct communication of breast lymphatic drainage with the intrapulmonary lymphatic system provides a potential mechanism for this pattern of spread. This case highlights how the combination of functional and anatomical information provided by SPECT/CT in lymphoscintigraphy continues to improve our understanding of potential paths of cancer spread.…”

Clinical Application of Multidetector Row Computed Tomography in Patient With Breast Cancer

“…An autopsy series of women who died of disseminated breast cancer revealed metastatic involvement of intrathoracic LNs in 71% of cases. 25 The second most common site of distant metastasis is bone, and bone metastasis is detected in 31% of all patients with metastasis. 26 Radiologically, skeletal metastases could be either lytic or sclerotic lesions or a combination of both (Fig.…”