Mammary Analogue Secretory Carcinoma of Salivary Gland

Definition

This is a recently described subtype of salivary gland carcinoma, analogous to secretory carcinoma of the breast and similar tumours arising in skin3,4. It comprises solid and microcystic areas, the microcysts being filled with vacuolated colloid-like PAS-positive material.

Epidemiology

The tumour occurs across a wide adult age range and equally in men and women.

Clinical features

It is most commonly found in the parotid gland, less often in minor salivary glands2. It is typically slow growing over many years.

Macroscopic appearances

The tumour are white/tan/grey, rubbery in consistency. They may be multinodular or cystic.

Histopathology

Tumour borders are usually circumscribed but there is often invasion of salivary gland or extra-salivary tissues. The tumour is dissected by fibrous septa. The epithelial component forms solid sheets, tubules, macrocysts and microcysts. The microcysts contain colloid-like material, which stains with PAS, resistant to diastase, and with mucicarmine, which may give an appearance resembling thyroid tissue. The tumour cells have granular eosinophilic (not basophilic) cytoplasm, vesicular nuclei with fine chromatin and a central nucleolus. Atypia is mild and the mitotic rate low. Perineural invasion has been reported2. Vascular invasion and necrosis are lacking. There is no overt squamous differentiation2.

Immunohistochemistry

Comparison with mammary secretory carcinoma and salivary gland acinic cell carcinoma is shown.

	Mammary Analogue Secretory Carcinoma	Mammary secretory carcinoma	Salivary gland acinic cell carcinoma
S-100	15/151, 5/72	4/41	4/121
Vimentin	15/151, 4/42	4/41	3/121
34bE12	6/72
Cam5.2	4/42
CK7	15/151	4/41	8/91
CK8	15/151	4/41	2/101
CK14	0/91, 0/22
CK18	15/151	4/41	9/101
CK19	15/151, 5/52	2/41	2/101
GCDFP-15	8/111, 3/5(focal staining in 3 cases)2	3/41	4/101
Mammaglobin	15/151	4/41	1/111
STAT 5a	15/151	4/41	7/111
MUC1	11/121	4/41	6/81
MUC4	9/111	4/41	0/81
EMA	9/91	4/41
p63	0/91, 0/62	0/41	0/61
SMA	0/72
Calponin	0/91, 0/72	0/41	0/61
EGFR	0/91	0/41	0/61
c-erbB-2	0/91	0/41	0/61
Oestrogen receptor	0/91	0/41	0/61
Progesterone receptor	0/91	0/41	0/61
Androgen receptor	0/91	1/41	0/61
Ki-67	5%-28%1	5%-10%1	5%-50%1

Molecular studies

There is typically a t(12;15)(p13;q25) translocation which gives rise to a chimeric tyrosine kinase . ETV6-NTRK3 fusion transcript was demonstrated in 20/21 cases1,2: this is the fusion product typical of secretory carcinoma of the breast1.

Differential diagnosis

Acinic cell tumour: the tumour is architecturally and cytologically heterogenous; there are large serous acinar cells with zymogen-like granules; they lack the ETV6-NTRK3 translocation
Cystadenocarcinoma NOS
Mucoepidermoid carcinoma
Adenoid cystic carcinoma
Low grade carcinoma, NOS

Prognosis

Behaviour is variable. There may be local recurrence, lymph node or distal metastases.

References

1 Skalova A, Vanecek T, Sima R, Laco J, Weinreb I, Perez-Ordonez B, et al. Mammary analogue secretory carcinoma of salivary glands, containing the ETV6-NTRK3 fusion gene: a hitherto undescribed salivary gland tumor entity. Am J Surg Pathol. 2010 May;34(5):599-608. (with clarification by the author of conflicts between text and tables)

2 Connor A, Perez-Ordonez B, Shago M, Skalova A, Weinreb I. Mammary analog secretory carcinoma of salivary gland origin with the ETV6 gene rearrangement by FISH: expanded morphologic and immunohistochemical spectrum of a recently described entity. Am J Surg Pathol. 2012 Jan;36(1):27-34.

3 Kazakov DV, Hantschke M, Vanecek T, Kacerovska D, Michal M. Mammary-type secretory carcinoma of the skin. Am J Surg Pathol. 2010 Aug;34(8):1226-7; author reply 8.

4 Brandt SM, Swistel AJ, Rosen PP. Secretory carcinoma in the axilla: probable origin from axillary skin appendage glands in a young girl. Am J Surg Pathol. 2009 Jun;33(6):950-3.