Radiology/Pathology Correlation

Unknown 10

A 58-year-old woman presented with progressive shortness of breath.

Chest Radiography

Figure 1

Frontal chest radiograph shows linear opacity primarily affecting the inferior and lateral portions of the right thorax. The linear opacities are lines perpendicular to and abutting the pleural surface, approximately 1-2 cm long. Linear opacities with this morphology represent interlobular septal thickening (also known as Kerley's B lines).

Figure 2. High-Resolution Computed Tomography (HRCT)

HRCT image through the right lower thorax shows smooth interlobular septal thickening and mild smooth bronchovascular thickening.

What is the differential diagnosis?

Answer

 


Pathology

This is an image of the cut surface of a lung from another patient with the same entity.

bronchuslobulelnwithlnwith2

Figure 3. Gross Appearance

Note the polygonal lines accentuating the interlobular septa. The lobular parenchyma shows prominence of bronchiolovascular bundles, best seen in the upper half of the image. A large bronchus at the upper right has a thickened wall. The black lymph nodes are partially replaced by white tissue.

Find the bronchus with a thickened wall. Click on the structure in the image to get verification.

Find a lobule with thickened interlobular septa and centrilobular thickening to the left and slightly below the thick-walled bronchus.

ils1ils2bvbundle

Figure 4. Histologic View of Above Lung

Find the thickened interlobular septa.

Find a thickened bronchiolovascular bundle.

 

cells1cells2airwaylymph1lymph1lymph2

Figure 5. Centrilobular Area

This image shows a partially recanalized arterial thrombus with cell clusters in two of the new lumens. Surrounding lymphatics are dilated and contain abnormal cells. The airway lies at the top. Note the fibrosis around the vessel. Elastic van Gieson stain

Find 2 cell clusters in the recanalized thrombus.

Find the airway.

Find 2 dilated lymphatics with abnormal cells.

What is the diagnosis?

Answer

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Pulmonary Lymphatic Carcinomatosis (PLC) (syn: lymphangitic carcinoma, carcinomatous lymphangitis) and Embolic Tumor (ET)

Discussion

Definitions and clinical aspects: The lung is a frequent site of metastasis for extrapulmonary and pulmonary solid malignant tumors. Patterns of metastatic spread to the lung include tumor in lymphatics and emboli to blood vessels not contiguous with extravascular tumor, as well as solitary or multiple extravascular nodules, endobronchial spread, or some combination. Embolic (ET) and lymphatic carcinomatosis (PLC), illustrated here and often lumped together clinically as PLC, may produce dyspnea, hypoxemia, and acute or subacute pulmonary hypertension and cor pulmonale [1]. In a study of ET and PLC in autopsy specimens, lesions were classified after examination of 15 sections from each case as ET, PLC, or both. Of the 89 cases studied, 17 (19%) showed ET, 41 (46%) showed PLC, and 31 (35%) showed both [2]. Symptoms were similar for all groups, but death from respiratory distress, and morphologic changes of pulmonary hypertension were more frequent in cases with ET [3].

Development: Embolic tumor destined for the lung invades veins or lymphatics at the primary site. Venous tumor spreads via the vena cava directly to the right heart and pulmonary artery. Tumor in lymphatics may spread via the thoracic duct or bronchomediastinal ducts to the subclavian veins, right heart, and pulmonary artery, but it may also spread retrograde to pulmonary lymphatics from thoracic lymphatics and lymph nodes. With primary lung tumors, vascular spread can occur via direct invasion. Tumor is rarely present in the interstitium between involved blood vessels and lymphatics, making it unlikely that direct spread occurs between the two.

Radiology: Chest radiographic manifestations of PLC include interlobular septal thickening, also referred to as Kerley's B lines, reticular opacities, nodules, pleural effusion, and lymphadenopathy. However, the chest radiograph is insensitive for the detection of PLC, and may be normal in nearly 50% of cases of proven PLC. HRCT is more sensitive than radiography for the detection and characterization of PLC. HRCT findings of PLC include [4,5]:

PLC is usually asymmetric and occasionally unilateral, but bilateral symmetric disease does occur. PLC may be diffusely distributed throughout a lung, or it may be relatively localized. The interlobular septal thickening that occurs with PLC is often smooth, in which case the differential diagnosis must include hydrostatic pulmonary edema, pulmonary hemorrhage, subacute infections (especially Pneumocystis Carinii pneumonia, alveolar proteinosis, and lipoid pneumonia). The finding of nodular, or "beaded," interlobular septal thickening is fairly characteristic of PLC, especially when asymmetric and accompanied by pleural effusion and lymphadenopathy. Both sarcoidosis and maltoma can result in nodular interlobular septal thickening, but usually the septa are rather inconspicuous in comparison to the numerous small nodules of these diseases. In contrast, thickened interlobular septa are often more prominent than small nodules in HRCT scans of patients with PLC.

Characteristically, PLC is not a fibrosing process within the lobule, so the architecture of the secondary pulmonary lobule is not disturbed. When the margins of the secondary lobule are thickened by tumor infiltration, the secondary lobule takes on a polygonal configuration, which is characteristic of PLC. Often the bronchiolovascular bundle is seen as a dot within the center of such polygons.

Pathology: ET and PLC may be bilateral, unilateral, focal, or diffuse. Although tumor emboli occasionally involve large, elastic arteries (atrial myxoma, hepatocellular cancer), most involve small muscular arteries, or less frequently, veins or capillaries. Emboli may cause thrombosis and be associated with microangiopathic hemolytic anemia [6]. Arterial occlusions may be associated with small infarcts. Thrombi may recanalize and rethrombose (see Figure 5 above). Lymphatics in any location--around the bronchovascular bundle, in interlobular septa, or in the pleura--may contain tumor. Over time, interstitial fibrosis occurs around tumor in these structures. Nodular interstitial tumor and carcinomatous "pneumonia" may accompany ET and/or PLC.

Diagnosis: A pattern of PLC on HRCT is highly suggestive of the diagnosis. Without this pattern, ET may still be a possibility in patients with known tumors and in those who present with dyspnea without a diagnosis of cancer. In these patients, for whom the differential diagnosis includes thromboembolism, HRCT may show a dilated and beaded appearance of peripheral pulmonary arteries [7], ventilation/perfusion scans may show a "segmental contour" pattern, and angiograms are usually not diagnostic of thromboemboli [1]. Arterial blood aspirated from small vessels via a wedged right heart catheter may show tumor [1]. Alternatively, in ET/PLC, examination of sputum cytology, bronchial washings, or lavage fluid may reveal tumor [8]. Definitive diagnosis of ET/PLC rests on lung biopsy [1].

Molecular mechanisms of ET/PLC: Studies have shown that metastasis depends on tumor-produced enzymes that degrade extracellular fibers and matrix [9]. Whereas these mechanisms explain how tumors gain access to the blood or lymphatics and exit from the vascular spaces, they do not explain why tumor tends to remain confined to blood vessels and lymphatics in patients with ET/PLC.

Outcome: While most patients with ET/PLC die within a few months of diagnosis, long term survival up to 30 months has been reported, and radiographs may show temporary regression or stability with chemotherapy [10].

Summary of Radiographic Features

Summary of Pathologic Features of ET and PLC

Diagnosis: Pulmonary embolic and lymphatic carcinomatosis (breast cancer primary)

References: To return to reference section after viewing abstract, click here before clicking on "abstract".

1. Bassiri A, Haghighi B, Doyle R, Berry G, Rizk N. Pulmonary tumor embolism. Am J Respir Crit Care Med 1997; 155:2089-2095.

2. Soares F, Landell G, Mello de Oliveira J. Clinical aspects of tumour involvement of the pulmonary vessels. Acta Oncologica 1992; 31:519-523. Abstract

3. Soares F, Pinto A, Landell G, Mello de Oliveira J. Pulmonary tumor embolism to arterial vessels and carcinomatous lymphangitis. A comparative clinicopathological study. Arch Pathol Lab Med 1993; 117:827-831. Abstract

4. Johkoh T, Ikezoe J, Tomiyama N, Nagareda T, Kohno N, Takeuchi N, et al. CT findings in lymphangitic carcinomatosis of the lung: correlation with histologic findings and pulmonary function tests. AJR 1992; 158:1217-1222. Abstract

5. Munk P, Muller N, Miller R, Ostrow D. Pulmonary lymphangitic carcinomatosis: CT and pathologic findings. Radiology 1988; 166:705-709. Abstract

6. Rytting M, Worth L, Jaffe N. Hemolytic disorders associated with cancer. Hematol/Oncol Clin N Am 1996; 10:365-376.

7. Shepard J, Moore E, Templeton P, McLoud T. Pulmonary intravascular tumor emboli: dilated and beaded peripheral pulmonary arteries at CT. Radiology 1993:187:797-801. Abstract

8. Levy H, Horak D, Lewis M. The value of bronchial washings and bronchoalveolar lavage in the diagnosis of lymphangitic carcinomatosis. Chest 1988; 94:1028-1030. Abstract

9. Zetter B. The cellular basis of site-specific tumor metastasis. N Engl J Med 1990; 322:605-612.

10. Ikezoe J, Godwin J, Hunt K, Marglin S. Pulmonary lymphangitic carcinomatosis: chronicity of radiographic findings in long-term survivors. AJR 1995; 165:49-52. Abstract

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Last modified 1/12/03

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

The term "lymphatic" is used here rather than "lymphangitic," which connotes an inflammatory component. Inflammation is absent in this type of tumor spread.

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Differential diagnosis: The differential diagnosis of interlobular septal thickening includes hydrostatic pulmonary edema, lymphatic spread of carcinoma, pulmonary hemorrhage, alveolar proteinosis, lipoid pneumonia, subacute infections, and lymphomas of the bronchial mucosa-associated tissues (maltomas).

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Bronchus with thickened wall

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Lobule with thickened centrilobular nodule that is partly surrounded by thickened interlobular septa

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Lymph node partly replaced by white tissue

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Thickened interlobular septa

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Thickened bronchiolovascular bundle

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Cell cluster in recanalized lumen

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Airway

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Dilated lymphatic with abnormal cells

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Embolic and lymphatic tumor. Embolic tumor is defined as tumor in vessels away from a primary tumor or parenchymal metastatic focus. It may be in arteries, veins, or capillaries. Lymphatic tumor is tumor in lymphatics around bronchovascular bundles, in interlobular septa, and in the pleura. Although morphologically the two types of tumor spread may occur separately, they often occur together in some combination. Radiographic features differ in the pure forms, but clinical features are similar for both types. The perivascular fibrosis and the recanalized thrombus indicate a chronic process.

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