Pleomorphic adenoma of the lung

Definition

A biphasic lung tumour consisting of glands and myoepithelial cells in a myxoid stroma, with similarities to that seen in salivary glands. However, positivity for TTF-1 shows that the epithelial component is differentiating towards type II alveolar cells3.

Epidemiology

This is a rare tumour, which may occur in children but has most often been reported in the elderly.

Clinical features

Presentation is often with obstructive symptoms1.

Radiology

Most often central and endobronchial, some cases are peripheral and form a well circumscribed mass1,2.

Macroscopic appearances

Endobronchial cases are polypoidal. The tumour is circumscribed, rubbery to myxoid.

Histopathology

The appearances are those of a "cellular mixed tumour", consisting of epithelial and myoepithelial cells in sheets, ducts and trabeculae. There is a myxoid stroma. They differ from salivary gland tumours in lacking both a prominent glandular component and a well developed chondroid stroma. Mitoses, pleomorphism and necrosis are not features.

There may be transition for a benign biphasic tumour to adenosquamous carcinoma or spindle cell sarcoma3.

Immunohistochemistry

	ductal and myoepithelial cells	stromal cells
Cam 5.2	positive1
broad spectrum cytokeratins	positive1	1/1(AE1/AE3)3
vimentin	less strongly positive1	positive
SMA	less strongly positive1	positive, 1/13
GFAP	variably positive1	variably positive1
S-100	variably positive1	variably positive1, 1/13
TTF-1	positive
PE-10	positive

Ultrastructure

Differential diagnosis

Hamartoma: show cartilage and other mesenchymal elements.
Pulmonary blastoma: obviously malignant stroma.
Carcinosarcoma: obviously malignant stroma.

Management

Prognosis

Behaviour varies from benign to malignant1,4. Larger tumours, infiltrative margins, cytological atypia, necrosis, angio-invasion and more than 5 mitoses / 10 HPF are markers of malignancy.

References

Tumours of the Lung, Pleura, Thymus and Heart. WHO Classification of Tumours. IARC Press 2004.

1 Moran CA, Suster S, Askin FB, et al. Benign and malignant salivary gland-type mixed tumors of the lung. Clinicopathologic and immunohistochemical study of eight cases. Cancer 1994; 73:2481-90

2 Sakamoto H, Uda H, Tanaka T, et al. Pleomorphic adenoma in the periphery of the lung. Report of a case and review of the literature. Arch Pathol Lab Med 1991; 115:393-6

3 Hayes MM, van der Westhuizen NG,Forgie R Malignant mixed tumor of bronchus: a biphasic neoplasm of epithelial and myoepithelial cells. Mod Pathol 1993; 6:85-8

4 Takeuchi E, Shimizu E, Sano N, et al. A case of pleomorphic adenoma of the lung with multiple distant metastases--observations on its oncogene and tumor suppressor gene expression. Anticancer Res 1998; 18:2015 -20

5 Matsumoto M, Sonobe H, Furihata M, et al. A case of salivary gland-type mixed tumor of the lung differentiating toward type II alveolar epithelial cells in glandular components with a literature review. Virchows Arch 2002; 441:618-21

This page last revised 20.11.2008.