Basal cell adenocarcinoma of salivary gland

This is a low grade adenocarcinoma. The cytological appearances are bland, but the growth pattern indicates malignancy. About 75% of basal cell adenocarcinomas arise de novo, about 25% from pre-existing basal cell adenomas.

Clinical features

This is a rare tumour, accounting for 2.9% of all malignant salivary gland tumours2. 90% arise in the parotid gland, the remainder in the submandibular gland or rarely in the palate, minor salivary glands, nasal cavity and paranasal sinuses. Like basal cell adenomas, there is an association with dermal cylindromas.

Histopathology

The tumors are unencapsulated with infiltrative margins. The predominant patttern is of solid groups of cells surrounded by thick PAS-positive basal laminae. The basement lamina material may also form intercellular droplets. Less often, there is a tubular pattern.

There are two cell types in variable proportions. Small cells have scanty cytoplasm and hyperchromatic nuclei are found predominantly at the periphery of nests. Larger polygonal cells with eosinophilic or pale cells and pale round nuclei are found at the centre of nests. Mitotic rates are usually 2-3/10 HPF. Necrosis, perineural invasion and vascular invasion may be seen.

Immunohistochemistry

	Cam5.2	positive
	AE1/AE3	positive
	CEA	positive, especially larger pale cells
	Cytokeratin 5/6	positive
	S-100	positive, especially small peripheral cells
	SMA	positive, especially small peripheral cells
	Muscle-specific actin	positive, especially small peripheral cells
	Vimentin	positive
	EMA	variable
	Ber-EP4	variable
	GFAP	negative or focally positive

Ultrastructure

Desmosomes are present. The larger cells show more glycogen and fewer filaments. At the periphery of nests, there are elongated cells with pinocytotic vesicles and myofilaments.

Differential diagnosis

Basal cell adenoma: lacks an invasive growth pattern
Solid variant of adenoid cystic carcinoma
Pleomorphic adenoma
Basal cell carcinoma of the skin infiltrating parotid gland
basaloid squamous cell carcinoma

Prognosis

These are low-grade malignancies with a low mortality but low recurrences in about one third of patients. Cervical lymph node metastases may occur. Those tumours arising in minor salivary glands may be more aggressive.

References

1Perez-Ordonez B. Selected topics in salivary gland tumour pathology. Current Diagnostic Pathology 2003;9:355-365.

2Eliis GL, Auclair PL. Malignant epithelial tumours in: Tumors of the Salivary Glands. Armed Forces Institute of Pathology, Washington DC. Atlas of Tumor Pathology, 3rd Edition, 1996;15-373.

This page last revised 8.2.2004.