Discussion
Diagnosis With Brief Discussion
- Diagnosis
- Pulmonary Langerhans cell histiocytosis (LCH)
- Radiologic Findings
- Initial chest radiograph shows diffuse coarse reticulonodular opacities in both lungs with upper lung predominance and relative sparing of both costophrenic angle areas.Chest CT shows wide-spreading solid and cavitary nodules and cysts with variable size and upper lung predominance in both lungs and nodules are located in centrilobular areas with relative sparing of both cardiophrenic angle areas.
- Brief Review
- LCH was formerly known by various names such as histiocytosis X, eosinophilic granuloma, Letterer-Siwe disease, and Hand-Schu¨ ller-Christian syndrome. LCH is an abnormal nonmalignant
proliferation of monoclonal Langerhans cells within one or multiple organ systems. Although the etiology of LCH is unknown, theories include viral infection, antigen exposure, and somatic mutation. Pulmonary LCH refers to LCH isolated to the respiratory system, notably the lungs. This rare disease is found almost exclusively in cigarette smokers, which supports the theory of antigen
exposure, since cigarette smoke contains thousands of known antigens. Pulmonary LCH appears to begin in the third to fourth decade of life, but a patient with mild to moderate disease may not receive a diagnosis until later. The most common clinical symptoms include dyspnea, cough, and fatigue, although patients may present with chest pain caused by a pneumothorax. For most patients, symptom stabilization occurs with smoking cessation alone.
The radiologic findings of pulmonary LCH vary depending on the stage of the disease at diagnosis. Diffuse bilateral ill-defined nodules will be seen in early stages. Because the disease has an inhalational component, the middle and upper lung zones are involved to a greater extent than the lung bases. It is thought that these nodules undergo cystic degeneration as the disease progresses, and so a reticular pattern begins to predominate on chest radiographs as the numerous cystic walls are superimposed on one another. The cysts and residual parenchyma can undergo fibrosis over time and eventually lead to changes of honeycombing. On HRCT, many cysts appear round, they can also have bizarre shapes, being bilobed, cloverleaf shaped, or branching in appearance. These unusual shapes are postulated to occur because of fusion of several cysts, perhaps because the cysts sometimes represent ecstatic and thick-walled bronchi. In some patients, cysts are the only abnormality visible on HRCT, small nodule are also present. They were usually smaller than 5mm in diameter. Larger nodules, sometimes exceeding 1cm, may also be seen, but they are less common. The margins of nodules are often irregular, particularly when there is surrounding cystic or reticular disease. Many nodules can be seen to be peribronchial or peribronchiolar and therefore centrilobular in location. The nodules are usually homogenous in appearance, but some nodules, particulary those large than 1cm in diameter, may show lucent centers, presumably corresponding to small cavities. HRCT image classically shows upper to mid lung zone predominance in size and number of nodules or cysts with sparing area of costophrenic angles. Phenotypically, LCs express surface CD1a glycoprotein and cytoplasmic S-100 protein, although the latter is not specific.
- References
- 1. Danny L. Leatherwood, Darel E. Heitkamp, Robert E. Emerson. Best Cases from the AFIP Pulmonary Langerhans Cell Histiocytosis
2. Aubry MC, Wright JL, Myers JL. The pathology of smoking-related diseases.
- Keywords
- lung, lymphoproliferative disease,