Small cell carcinoma of salivary gland

Small cell carcinoma of salivary gland

Epidemiology

Small cell carcinoma of the salivary gland accounts for less than 1% of salivary gland tumours2, less than 2% of salivary gland malignancies. They are found predominantly in major salivary glands, particularly the parotid gland. There is a male predominance, with a peak incidence in the fifth to seventh decades.  The lack of positivity for the Merkel cell polyomavirus in primary parotid high-grade neuroendocrine carcinoma, whether or not positive for CK20, argues that these tumours are distinct from Merkel cell carcinoma4.

Histopathology

The tumour is composed of small cell with scant cytoplasm; nuclei have fine chromatin and lack nucleoli.

This is probably a heterogeneous group of tumours with variable immunophenotypes:

 

Merkel cell type

Pulmonary type

Ductal type

nuclear morphology

plump, delicate chromatin, pale, "washed out", nuclear moulding not prominent

elongated with dense chromatin and nuclear moulding. crush artefact is common.

 

architecture

 

pseudorosettes and fibrillary cytoplasm

focal glandular and/or squamous differentiation

 

Immunohistochemistry

 

Overall

Merkel cell type

Pulmonary type

Ductal type

pan-cytokeratin

14/152 

positive

positive

positive

AE1/3

14/152

 

 

 

Cam5.2

13/152

 

 

 

EMA

14/152

 

 

 

CK7

5/152

 

 

 

CK20

3/51, 11/152

 

positive

negative

negative

synaptophysin

10/152 

positive

positive

negative

chromogranin

13/152 

positive

positive

negative

neurofilament

6/152

 

 

 

CD56

5/152

 

 

 

CD57

4/152

 

 

 

NSE

15/152

 

 

 

p53

8/152

 

CEA

4/152

 

TTF-1

3/152

negative in most of the few cases studied

S-100

0/152

 

 

 

HHF-35

0/152

 

 

 

SMA

0/152

 

 

 

vimentin

0/152

 

 

 

LCA

0/152

 

 

 

HMB-45

0/152

 

 

 

         

Differential diagnosis

Prognosis

More than half of patients develop lymph node and/or distant metastases2. Two and five year survivals are 38 to 70% and 13 to 46% respectively, which is superior to small cell carcinoma of the lung and larynx. CK20-positive (Merkel cell type) small cell carcinoma of salivary glands may have a better prognosis2.

References

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

1 Chan, J. K., S. Suster, et al. (1997). "Cytokeratin 20 immunoreactivity distinguishes Merkel cell (primary cutaneous neuroendocrine) carcinomas and salivary gland small cell carcinomas from small cell carcinomas of various sites." Am J Surg Pathol 21(2): 226-34.

2 Nagao, T., T. A. Gaffey, et al. (2004). "Small cell carcinoma of the major salivary glands: clinicopathologic study with emphasis on cytokeratin 20 immunoreactivity and clinical outcome." Am J Surg Pathol 28(6): 762-70.

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

4 Chernock RD, Duncavage EJ, Gnepp DR, El-Mofty SK, Lewis JS, Jr. Absence of Merkel cell polyomavirus in primary parotid high-grade neuroendocrine carcinomas regardless of cytokeratin 20 immunophenotype. Am J Surg Pathol. 2011 Dec;35(12):1806-11.

This page last revised 15.7.2007.