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.
This is a rare tumour, which may occur in children but has most often been reported in the elderly.
Presentation is often with obstructive symptoms1.
Most often central and endobronchial, some cases are peripheral and form a well circumscribed mass1,2.
Endobronchial cases are polypoidal. The tumour is circumscribed, rubbery to myxoid.
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.
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ductal and myoepithelial cells |
stromal cells |
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positive1 |
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positive1 |
1/13 |
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less strongly positive1 |
positive |
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less strongly positive1 |
positive, 1/13 |
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variably positive1 |
variably positive1 |
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variably positive1 |
variably positive1, 1/13 |
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positive |
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positive |
|
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Hamartoma: show cartilage and other mesenchymal elements.
Pulmonary blastoma: obviously malignant stroma.
Carcinosarcoma: obviously malignant stroma.
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.
Tumours of the Lung, Pleura, Thymus and Heart. WHO Classification of Tumours. IARC Press 2004.
This page last revised 20.11.2008.
©SMUHT/PW Bishop