Radiology/Pathology Correlation

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A 40-year-old woman presents with progressive shortness of breath.

Radiology

Chest Radiograph

Describe the findings of the frontal chest radiograph.

Are effusions or adenopathy present? Answers

 

High Resolution CT

Describe the CT.

Give a diffential diagnosis. Answers


Pathology

 

 

Gross Appearance of Lung

This image shows the same disease that occurred in a different patient.

Thin-walled cystic spaces of varying size are scattered throughout the otherwise normal parenchyma. Subpleural cysts, which cause diffuse pleural bulges that suggest the diagnosis, predispose to pneumothorax.

The texture on palpation is normal, in contrast to emphysema, which is softer than normal, or fibrosis with honeycombing, which is firmer than normal.

Also, in contrast to emphysema in which the alveolar walls crumple when fixative escapes, the cyst walls remain upright.

 

 

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Histopathology

A histologic section shows slight thickening of the cyst walls (former alveolar walls) by a proliferation of cells. Adjacent alveolar walls are normal.

Find and outline 3 of these cyst walls. Click on the structure in the image to get verification.

What is the diagnosis?

What is the cell type that is proliferating?

Answers

 

 

 

 

Comments on the Radiographic Features

Most commonly, the chest radiograph in patients with lymphangioleiomyomatosis shows diffuse, bilateral, symmetric, reticular opacities. In a minority of cases, reticulation is most evident in the lower lung zones. The discrete cysts of LAM may be evident on the radiograph in approximately 50% of patients. Lung volumes are typically large. Pleural effusions (unilateral or bilateral) are seen in nearly 20% of patients, and spontaneous pneumothorax may be a presenting feature of the disease [1,2].

The characteristic HRCT findings of LAM are numerous, thin-walled cysts with normal intervening lung parenchyma. (For another example, click here. Use the "back" button in the menu bar to return.) Cysts typically range in size from a few millimeters to several centimeters. The cysts are distributed diffusely throughout the lungs, with no zonal predominance. Pleural effusions may be evident, and mild lymphadenopathy may occasionally be encountered. An identical imaging appearance may be seen in patients with tuberous sclerosis and pulmonary LAM, having been described in over 30% of tuberous sclerosis patients who have no pulmonary symptoms [3,4]. In the latter patients, cysts were less frequent than in those with symptomatic lung disease and tended to involve the mid or upper lung or peripheral zones [3]. Quantification of changes on HRCT show good correlations with FEV1(%), DLco(%), and RV/TLC(%) [5].

Comments on the Histopathologic Features

Pulmonary LAM is a disease characterized by the proliferation of smooth muscle-like cells around small airways, blood vessels, and lymphatics, and in alveolar walls resulting in cyst formation [6,7]. The proliferating cells differ from normal smooth muscle cells in their morphology and staining. Recently, these cells have been designated perivascular epithelioid cells (PEC), based on the rounded morphology of cells of early lesions around vessels [8]. Although a normal counterpart is not known, the cells have the same genetic and immunohistochemical characteristics as those in angiomyolipomas, which often accompany LAM. The PECs apparently have the ability differentiate into fat and vessels, as well as smooth muscle [8]. In cases of sporadic LAM, both the LAM cells in the lung and the cells of angiomyolipomas have been shown to have identical clonal, somatic mutations of the TSC2 gene of tuberous sclerosis, whereas the surrounding uninvolved tissue had a normal genotype [9]. This finding suggests that there may be spread (metastasis) from one lesion to another and gives a possible explanation for recurrence of the disease in lung transplants.

Factors linking sporadic LAM to tuberous sclerosis [7,9]

The characteristic symptoms and signs of airflow obstruction, cyst formation, pneumothorax, chylothorax, and hemoptysis, can be explained at least in part by the histopathology.

Final diagnosis: Lymphangioleiomyomatosis, sporadic

References

1. Müller N, Chiles C, Kullnig P. Pulmonary lymphangiomyomatosis: correlation of CT with radiographic and functional findings. Radiology 1990; 175:335-339. abstract

2. Kalassian K, Doyle R, Kao P, Ruoss S, Raffin T. Lymphangioleiomyomatosis: new insights. Am J Respir Crit Care Med 1997; 155:1183-1186.

3. Franz D, Brody A, Meyer C, Leonard J, Chuck G, Dabora S, Sethuraman G, Colby T, et al. Mutational and radiographic analysis of pulmonary disease consistent with lymphangioleiomyomatosis and micronodular pneumocyte hyperplasia in women with tuberous sclerosis. Am J Respir Crit Care Med 2001; 164:661-668. abstract

4. Moss J, Avila N, Barnes P, Litzenberger R, Bechtle J, Brooks P, Hedin C, Hunsberger S, Kristof A. Prevalence and clinical characteristics of lymphangioleiomyomatosis (LAM) in patients with tuberous sclerosis complex. Am J Respir Crit Care Med 2001; 164:669-671. abstract

5. Avila N, Kelly J, Dwyer A, Johnson D, Jones E, Moss J. Lymphangioleiomyomatosis: correlation of qualitative and quantitative thin-section CT with pulmonary function tests and assessment of dependence on pleurodesis. Radiology 2002; 223:189-197. abstract

6. Corrin B, Liebow A, Friedman P. Pulmonary lymphangiomyomatosis. A review. Am J Pathol 1975; 79:348-382.

7. Pacheco-Rodriguez G, Kristof A, Stevens L, Zhang Y, Crooks D, Moss J. Genetics and gene expression in lymphangioleiomyomatosis. Chest 2002;121:56S-61S. abstract

8. Bonetti F, Pea M, Martignoni G, Zamboni G, Manfrin E, Colombari R, Mariuzzi G. The perivascular epithelioid cell and related lesions. Review article: new unifying concept. Advances in Anatomic Pathol 1997; 4:343-358.

9. Yu J, Astrinidis A, Henske E. Chromosome 16 loss of heterozygosity in tuberous sclerosis and sporadic lymphangiomyomatosis. Am J Respir Crit Care Med 2001; 164:1537-1540. abstract

Last revised 5/15/02

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The chest radiograph shows large lung volumes with symmetric, bilateral linear and reticular (fine criss-cross lines) opacities. There is no evidence of adenopathy or effusion.

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The HRCT of the chest shows diffuse, uniform, thin-walled cystic spaces without evidence of honeycombing (cysts with thick walls), nodules, or fibrosis.

Differential Diagnosis: Lymphangioleiomyomatosis, Langerhans' cell histiocytosis (cyst walls usually thick; nodules often present) (Use the "back" button in the menu bar to return.), emphysema (cyst walls often invisible), pneumatoceles from Pneumocystis carinii pneumonia. Bronchiectasis, cystic metastases, septic pulmonary emboli and infarction, Wegener's granulomatosis, and idiopathic interstitial pneumonias give thicker-walled cysts that can usually be distinguished from the thin-walled cysts.

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Thickened alveolar wall around cyst

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Diagnosis: Lymphangioleiomyomatosis. The cell type is a smooth muscle-like cell, recently designated a perivascular epithelioid cell (PEC).

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