Polymorphous low-grade adenocarcinoma of the salivary gland, PLGA

This is a low-grade malignancy characterised by bland cytology and various architectural patterns.

Epidemiology

This tumour constitutes 19.6% of malignant salivary gland tumours1.

Clinical features

Patients are usually middle-aged to elderly, more often women. Minor salivary glands of the palate, buccal mucosa, upper lip. retromolar region, floor of mouth, posterior tongue or nasal cavity may be involved. Involvement of major salivary glands is uncommon, but PLGA may occur as the carcinomatous component of carcinoma ex-pleomorphic adenoma.

Histopathology

The tumour is well circumscribed at low power, but the margins show foci of infiltration. There are various architectural patters:

The tumour cells are embedded within a myxoid or mucohyaline stroma. Perineural infiltrations is the rule and perivascular infiltration common: cells often surround these structures in a targetoid arrangement. Psammoma bodies may be present.

The cells are bland and are variable small cuboidal, round, polygonal or spindle. Chromatin is fine and nucleoli are not prominent. The mitotic rate is about 1/10HPF. Atypical mitoses are not seen.

 

Immunohistochemistry

cytokeratin

positive

AE1/AE3

21/212

CK7

21/212

CK20

0/212

EMA

positive

S-100

positive

bcl-2

positive

vimentin

positive

CD117

may be positive1

actin

variably focal/weak

CEA

focal or negative1

GFAP

usually negative, at most only focal1

Calponin

negative1

   

Differential diagnosis

Prognosis

There may be progression to high grade carcinoma after several recurrences.

References

Diagnostic histopathology of tumors. Edited by CDM Fletcher. 2nd edition. Churchill Livingstone. Page 275.

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

2 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.