Hyalinising clear cell carcinoma of the salivary gland, HCCC

This is an uncommon salivary gland tumour composed exclusively of clear cells containing abundant glycogen. It has been variously considered a form of clear cell adenocarcinoma or a variant of squamous cell carcinoma.

Clinical features

90% of cases involve minor intraoral salivary glands⁴, but rarely cases in the tongue, parotid gland and larynx have been reported.

Histopathology

The clear cells are arranged in trabeculae, cords, nests and sheets surrounded by a hyalinised PAS-positive stroma. The stroma may be focally myxoid. There is no glandular or ductal architecture. Mucin stains are negative⁴. The cells cytoplasm varies from clear to palely eosinophilic. Nuclei are slightly irregular. Nucleoli may be seen but are not prominent.

Immunohistochemistry

cytokeratin	positive^1,4
AE1/AE3	1/1⁵
CK7	1/1⁵
CK20	0/1⁵
EMA	positive^1,4
CEA	focal positivity¹
S-100	negative^1,4
Calponin	negative¹
SMA	negative^1,4
Collagen I	stroma positive in 3/3²
Collagen III	stroma positive in 2/3²
Collagen IV	positive only around tumour cells, not in the interstitial stroma²
Laminin	positive only around tumour cells, not in the interstitial stroma²
Fibronectin	stroma positive in 3/3²
Tenascin	positive in stroma at advancing front of the tumour²

Ultrastructure

There is abundant cytoplasmic glycogen. Desmosomes, peripheral tonofilaments and interdigitating microvilli are seen⁴. There may be basal lamina reduplication and large deposits of long space collagen². There are no actin myofilaments to indicate myoepithelial differentiation.

Differential diagnosis

There are a number of primary salivary gland tumours which may have a clear cell appearance:

clear cell variants of myoepithelioma, benign and malignant
clear cell variant of epithelial/myoepithelial carcinoma
sebaceous adenoma and carcinoma
mucoepidermoid carcinoma
oncocytoma
acinic cell carcinoma

Prognosis

About 20% of cases have metastasised to neck lymph nodes. This is a low-grade malignancy with a recurrence rate of 17%. Pulmonary metastases may occur³ but no patient deaths have been reported.

References

Diagnostic histopathology of tumors. Edited by CDM Fletcher. 2nd edition. Churchill Livingstone. Page 283.

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

² Felix, A., J. C. Rosa, et al. (2002). "Hyalinizing clear cell carcinoma of salivary glands: a study of extracellular matrix." Oral Oncol 38(4): 364-8.

³ Wang, B., M. Brandwein, et al. (2002). "Primary salivary clear cell tumors--a diagnostic approach: a clinicopathologic and immunohistochemical study of 20 patients with clear cell carcinoma, clear cell myoepithelial carcinoma, and epithelial-myoepithelial carcinoma." Arch Pathol Lab Med 126(6): 676-85.

⁴ Milchgrub, S., D. R. Gnepp, et al. (1994). "Hyalinizing clear cell carcinoma of salivary gland." Am J Surg Pathol 18(1): 74-82.

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.