Case 26--Continued

Section 3

Histologic Findings

This early lesion would not be visible by HRCT. It has a centrilobular location characterized by an interstitial infiltrate that widens bronchiolar and alveolar interstitium. The lesion is accompanied by increased numbers of alveolar macrophages.

Find the pulmonary artery that identifies a bronchiolovascular bundle. The respiratory bronchiole lies above it.

Outline the area of interstitial thickening.

Find 2 areas of emphysema probably related to cigarette smoking.


Nodular Shapes

Nodules may be star-shaped (stellate) or rounded. This star-shaped, subpleural nodule cannot be localized with respect to anatomic structures, but it may have arisen centrilobularly, as seen in the above picture.

Stellate Nodule

Note that the center is pinker (more fibrotic) than the edges, which are cellular. The deep blue area is an aggregate of lymphoid tissue.

Destruction of alveolar walls around the nodule produces so-called pericicatricial emphysema (emphysema around a scar).

These nodules may scar completely or cavitate.

Outline the nodule.


Round, Cavitary Nodule

This rounded, cellular nodule has a cavity. Although the nodule probably began centrilobularly, the normal landmarks have been destroyed. This nodule corresponds to the small nodule with cavitation on image 2 of the HRCT (use the "back" button in the menu bar to return).

Cavitary Nodule or Cyst

This cavitary lesion corresponds to the large cysts on the HRCT. Note that part of the wall is fibrotic and part is cellular. The adjacent alveoli are normal.

Cellular Features

At high magnification, cellular areas show Langerhans' histiocytes and variable numbers of eosinophils. The Langerhans' cell nuclei have clefts or appear lobulated. Cytoplasm is abundant, but cell borders are ill-defined. Antibodies to CD1a are used to identify the Langerhans' cells.

Find 3 eosinophils.

Find 2 Langerhans' histiocytes with clefts in the nucleus.

Find 2 Langerhans' histiocytes with lobulated nuclei.

Note that true granulomas are absent.


Differential diagnosis of multiple lung cysts on HRCT: Langerhans' cell histiocytosis, lymphangioleiomyomatosis, and pneumatoceles (commonly seen with pneumocystis pneumonia). Occasionally, cavitary infectious or inflammatory diseases, such as tuberculosis, sarcoidosis, rheumatoid arthritis with nodules, or Wegener's granulomatosis, can have a similar appearance. Cystic bronchiectasis can appear as diffuse cysts, and honeycomb lung appears as numerous cysts, usually in the periphery of the lung.

Histologic differential diagnosis: Langerhans' cell histiocytosis, respiratory bronchiolitis/desquamative interstitial pneumonia (histiocytes are CD1a negative), eosinophilic pneumonia (usually has more alveolar infiltrates), end-stage fibrotic lung (late disease)

Diagnosis: Langerhans' cell histiocytosis

Diagnostic features of Langerhans' cell histiocytosis on HRCT

Comment: HRCT images are often diagnostic of the disease.

See also Case Study 19.



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Pulmonary artery



























Interstitial thickening






























































Stellate nodule



























































Langerhans' cell with nuclear cleft
































Langerhans' cell with lobulated nucleus