Carcinoma ex pleomorphic adenoma of salivary gland, CXPA

This is a malignant epithelial tumour arising within a pleomorphic adenoma (mixed salivary gland tumour) and accounts for between 5% and 15% of all salivary gland malignancies. The risk of malignant transformation of pleomorphic adenoma is time dependent, with a risk of 1.6% for those present for less than 5 years, rising to 9.6% for those present for more than 15 years4. The malignant transformation most commonly occurs within the luminal cells, but in some cases shows dual epithelial-myoepithelial differentiation or is of pure myoepithelial differentiation.

Histopathology

Distribution of carcinoma subtypes in 70 patients with carcinoma ex pleomorphic adenoma1:

Adenocarcinoma NOS	31
Salivary duct carcinoma	24
Adenosquamous carcinoma	5
Undifferentiated carcinoma	3
Adenoid cystic carcinoma	3
Myoepithelial carcinoma	2
Epithelial-myoepithelial carcinoma	1
Sarcomatoid carcinoma	1

Immunohistochemistry

AE1/AE3	67/691, 11/115
CK7	65/691, 11/115
CK20	9/691, 0/115
EMA	59/691
CEA	52/691
Vimentin	36/691
S-100	20/691
Actin	5/691
GFAP	2/691
p53	28/691
c-erbB-2	21/691

Cyclin A may be helpful in the identification of CXPA:

	Cyclin A
	Pleomorphic adenoma	CXPA
Normal duct and acinar epithelium	0/284	0/124
Benign epithelium	11/284	5/104
Benign stroma	10/284	2/104
Malignant epithelium	N/A	12/144

Cytogenetics

CXPA commonly shows alterations of chromosome 8q21 and 12q13-15, as in the parent tumour. Loss of heterozygocisy at 12q may be a marker of potential for malignant transformation in pleomophric adenoma. Alterations of p53 and over-expression of c-erbB2 are common in CXPA3.

Prognosis

Prognostic factors include the extent of invasion beyond the capsule; in some papers 5 to 8 mm has been the critical extent. In the current WHO classification, tumour with invasion of less than 1.5 mm beyond the capsule are considered minimally invasive. Intracapsular and minimally invasive CXPA have almost no malignant potential2.

References

1 Lewis, J. E., Olsen, K. D., Sebo, T. J. Carcinoma ex pleomorphic adenoma: pathologic analysis of 73 cases. Human Pathol 2001;32:596-604.

2 Perez-Ordonez B. Selected topics in salivary gland tumour pathology. Current Diagnostic Pathology2003;9:355-365.

3 Cheuk W,Chan JK. Advances in salivary gland pathology. Histopathology 2007; 51:1-20

4 Patel RS, Hughes CW, Fredericks S, et al. Cyclin A expression and its diagnostic value in pleomorphic adenoma and carcinoma expleomorphic adenoma of the parotid gland. Histopathology 2007; 51:21-5

5 Meer S,Altini M. CK7+/CK20- immunoexpression profile is typical of salivary gland neoplasia. Histopathology 2007; 51:26-32

This page last revised 4.8.2007.