Teaching Case

A 53-year-old woman presented with symptoms of dyspnoea and non-productive cough, persistent for 7 weeks and not improving despite antibiotic therapy. She has been smoking for at least 35 years. Laboratory findings were normal. Initially Chest X-ray was performed.

Chest X-ray showed symmetric upper lung zone predominant reticulonodular opacities with multiple ill-defined nodules of 1-10 mm in diameter (Figure 1).
Further evaluation with CT confirmed this pattern and showed that some of these nodules presented with a central cavitation. These solid nodules showed stellate borders and were distributed in a peribronchiolar pattern. Furthermore, some small (< 10 mm) thick and thin walled irregular cysts were seen in the upper lobes (Figure 2). There were no signs of lung fibrosis and no lymphadenopathy or pleural fluid was present. A lung biopsy was performed and pathologic examination revealed eosinophilic granulomas in the context of pulmonary Langerhans cell histiocytosis.

Pulmonary Langerhans cell histiocytosis (PLCH) is an uncommon smoking-related granulomatous interstitial lung disease which is an isolated form of the multisystem disease of Langerhans cell histiocytosis.

Most common presenting symptoms are non-productive cough and dyspnoea.

On imaging, the elementary lesion is that of a bronchiolocentric evolving granuloma in the walls of the airways which is seen on HRCT as a peribronchiolar nodule. These solid nodules are usually smaller than 10 mm, have irregular borders and predominantly involving the middle and upper lung zones with relative sparing of the costophrenic angles [1].
Cavitation results from bronchiolar dilatation resulting from inflammation and fibrosis of the bronchiolar wall [2]. In its later stages, these cavitated nodules are replaced by thick walled cysts and finally by thin walled cysts. These cysts are also usually less than 10 mm in diameter and they can appear round or show more bizarre shapes.

PLCH can be strongly suggested in cases of a nodular pattern in presence of cavitated nodules and small cysts.
But in early stage of disease, when nodules are the only HRCT abnormality, differential diagnosis is extensive. Differentiation should be especially made with sarcoidosis, silicosis, tuberculosis and lung metastasis. Nodules in PLCH have a peribronchial and peribronchiolar distribution whereas perilymphatic nodules are typically seen in sarcoidosis, silicosis and lymphangitic carcinomatosis. A tree-in-bud pattern raises the possibility of endobronchial spread of tuberculosis.
When there are also cavitated nodules differentiation should be further made with Wegener granulomatosis, septic emboli and lung metastasis. Nodules in Wegener granulomatosis are usually larger, more delineated, have a more random distribution and cavitate in up to 50% of cases. In addition, presence of concomitant ground glass and consolidation favour the diagnosis of Wegener granulomatosis. Nodules seen in septic emboli show also stellate borders but they are more seen in the periphery of the lung bases. Metastatic nodular cavitation may occur in the squamous, sarcomatous or transitional cell carcinomas. They are better delineated and have a random vascular distribution [2, 3].
In the late chronic stadium of PLCH when lung cysts are the only abnormality differentiation should be made with centrilobular emphysema, desquamative interstitial pneumonia (DIP), Lymphangioleiomyomatosis (LAM) and Lymphocytic interstitial pneumonitis (LIP). In centrilobular emphysema focal areas of lung destruction lack visible walls. Concomitant patchy ground-glass opacity favours diagnosis of DIP. In women with LAM cyst have a round shape and no lung zone is spared. Cysts in patients with LIP have a lower lobe predominance [1].