Pneumocytic adenomyoepithelioma

Definition

A rare type of adenomyoepithelioma combining a dual population of pneumocytes and myoepithelial cells.

Macroscopic appearances

The tumour forms a well demarcated mass with a solid tan-white whorled cut surface.

Histopathology

The epithelial and myoepithelial components form double-layered glands. The epithelial layer is mildly pleomorphic. There may be solid epithelial nests. The glands are often filled with dense eosinophilic colloid-like material. There is an outer layer of cuboidal to attenuated cells. A minority of the tumour is composed of spindle cells.

Immunohistochemistry

	inner glandular cells	outer glandular cells	spindle cells
EMA	positive		negative
Cam5.2	positive	weakly positive	negative
CK7	positive	positive	positive
CK20	negative		negative
SP-A	positive		negative
TTF-1	positive	weakly positive	negative
high MW cytokeratin	negative		positive
S-100	negative	positive	positive
SMA	negative	positive	positive
p63	negative	positive	positive
calponin	negative	positive	positive
caldesmon
NSE	negative	negative	negative
Synaptophysin	negative	negative	negative
Chromogranin	negative	negative	negative
Desmin			negative
Thyroglobulin	negative	negative	negative
Ki-67	<5% of nuclei		<5% of nuclei

Ultrastructure

The epithelial cells are type II pneumocytes with lamellar bodies and short stubby microvilli. The spindle cells contain microfilaments with focal densities.

Differential diagnosis

Adenoma: lacks myoepithelial differentiation
Sclerosing haemangioma: lacks myoepithelial differentiation
Neuroendocrine tumours: are positive for neuroendocrine markers
Salivary gland type tumours

Management

Surgical excision is adequate.

Prognosis

These appear to be benign tumours.

References

1 Chang T, Husain AN, Colby T, et al. Pneumocytic adenomyoepithelioma: a distinctive lung tumor with epithelial, myoepithelial, and pneumocytic differentiation. Am J Surg Pathol 2007; 31:562-8

This page last revised 30.4.2007.