Basal cell carcinoma of salivary gland

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

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.

©SMUHT/PW Bishop