Lymphangitic carcinomatosis, or lymphangitis carcinomatosa, is the term given to tumor spread through the lymphatics of the lung and is most commonly seen secondary to adenocarcinoma.
The demographics will reflect that of the underlying malignancy (see below).
Clinical presentation is variable. Some patients experience dyspnea and abnormal pulmonary function tests early in the course of the disease, well before any radiographic abnormalities are evident, whereas others remain asymptomatic until much later .
Lymphangitic carcinomatosis is most commonly seen secondary to adenocarcinomas such as :
- breast cancer: most common
- lung cancer ( adenocarcinoma in situ)
- colon cancer
- stomach cancer
- prostate cancer
- cervical cancer
- thyroid cancer
A helpful mnemonic for lymphangitic carcinomatosis is sometimes used for its common causes.
Spread into the lymphatics in most cases (except in bronchogenic adenocarcinoma) usually occurs following haematogenous seeding of the lungs, with subsequent lymphatic involvement . It may also occur by retrograde spread into the lymphatics from the mediastinal and hilar lymph nodes.
Both the peripheral lymphatics coursing in the interlobular septa and beneath the pleura, and the central lymphatics coursing in the bronchovascular interstitium are involved .
Histologically tumor is seen both within lymphatics and in the adjacent interstitium, with associated edema and desmoplasia .
Radiographic appearances can most easily be divided into those due to the involvement of the peripheral (interlobular septa) and central lymphatic system. Involvement may be diffusely of both, or predominantly of one compartment or the other . Distribution of changes is variable, but most are asymmetric and patchy . It is usually bilateral but may be unilateral, especially in cases of lung and breast cancer.
Unfortunately up to a quarter of patients with subsequently established lymphangitic carcinomatosis have normal chest x-rays . When abnormal, the most common finding is a reticulonodular pattern, with thickening of the interlobular septa which may resemble septal (Kerley B) lines.
CT, especially HRCT, is excellent at demonstrating both peripheral and central changes.
Typically the appearance is that of interlobular septal thickening, most often nodular and irregular, although smooth thickening may also sometimes be seen . This results in a prominent definition of the secondary pulmonary lobules, manifesting as tessellating polygons.
There could also be an alveolar filling pattern blending into more reticulation .
Thickening of the bronchovascular interstitium is usually irregular and nodular, with changes seen extending towards the hilum .
The combination may give a characteristic "dot in box" appearance.
Additional HRCT findings include :
- subpleural nodules, and thickening of the interlobar fissures
- pleural effusion(s): pleural carcinomatosis
- hilar and mediastinal nodal enlargement (40-50%)
- relatively little destruction of overall lung architecture
A helpful sign is that the overall lung and lobular architecture is preserved . In most cases, lymphangitic carcinomatosis progresses rapidly and patients deteriorate (see treatment and prognosis below), however in some cases changes may remain stable over considerable time . As such a 'stable' appearance when compared to previous imaging does not necessarily exclude the diagnosis.
- increased avidity within the nodular interlobular septal thickening
- PET-CT has a sensitivity of 86% and specificity of 100%
Treatment and prognosis
Treatment is determined by the histology of the primary tumor, but in general, relies on systemic chemotherapy.
Prognosis of patients with lymphangitic carcinomatosis is poor, with approximately half of patients succumbing to their illness within a year of diagnosis . Occasionally, long-term survival is encountered .
Considerations include a differential for that of thickened interlobular septa, with common entities comprising of :