Carcinoma of the Salivary Glands

Secretory carcinoma is not just a breast cancer 

In the same year as the ETV6-NTRK3 fusion was reported in secretory carcinoma of the breast, Hirokawa and coworkers (2002) published a report proposing that acinic cell carcinoma of the salivary glands was the same entity as secretory carcinoma of the breast. Eight years later Alena Skálová  and coworkers (2010) confirmed this proposal. They examined  archives of FFPE preserved tumors that had histological characteristics of  secretory carcinoma of the breast as originally proposed by Hirokawa (2002).

Multiple institutions contributed 30 cases of salivary gland tumors with secretory features. The original diagnoses included

Of the 30 samples, 16 were reclassified as MASC.

Histological Features

All 16 tumors reclassified as MASC had morphology similar to that  shown in Figure 1

IHC images showing MASC morphology.

Figure 1 from Skálová 2010

The role of Trk signaling in lobular growth as it relates to the TEL-TrkC product of the ETV6-NTRK3 gene fusion is discussed elsewhere. If one browses H&E images from the history of MASC, unusual nuclei  with single nucleoli are an obvious recurring feature.

H&E images showing unusual nuclei with single nucleoli as an obvious recurring feature.

Figure 2 from Skálová 2010

Acrocentric chromosomes and the nucleoli are discussed on a sister site. These single, centrally located nucleoli seem to be a common feature of secretory carcinomas, not just MASC. True to the name, secreted material is also a common feature of salivary gland secretory carcinoma.

H&E images showing secreted material as a common feature of salivary gland secretory carcinoma.

Figure 3 from Skálová A 2010

The colloidal material is reminiscent of thyroid gland colloid. The periodic Schiff assay with diastase digestion (PAS-D)is discussed elsewhere.

Immunohisochemistry Features

Immunohistochemistry(IHC) uses antibodies to view the same structures stained with hematoxylin and eosin.  Hematoxylin is often used to stain nuclei. A chemical reaction catalyzed by an enzyme conjugated to an antibody system produces a  brown pigmentwhere antibodies are bound to tissue macromolecules.

Mucin-4

The mucin 4 protein consists of two subunits coded for by the same MUC4 gene. Mucin 4 is expressed in tissues such as thyroid, breast, and salivary glands as well as cancers that arise form these tissues. Mucin 4 may be anti-adhesive.  Mucin-4 may bind to and induce phosphorylation of the beast cancer associated receptor tyrosine kinase ERBB2, formally Her-2.

IHC image staining with Mucin-4 (Fig A). Fig. B show domains of Mucin-4 along with a cartoon showing structural imagination at the membrane site (Fig. C).

Figure 4.  Mucin-4 A From Skalova 2010 B. Domains of Mucin-4 C. Mucin-4 is a membrane bound protein with a heavily glycosylated extracellular domain

GCDFP-15

Some of the functions of gross cystic disease fluid protein 15 (GCDFP-15) can be discerned by its many aliases:

  • prolactin-inducible protein
  • extra-parotid glycoprotein (EP-GP)
  • gp17 seminal actin-binding protein (SABP).

Inside the cell Naderi and  Vanneste (2014) found that PIP/GCDGP-15 is necessary for tubulin polymerization, interacts with actin related protein 2/3, and promotes  breast cancer progression. Outside the cell, PIP can cleave fibronectin.  Fibronectin fragments can trigger cell signaling.

PIP/GCDGP-15 expression in normal tissue (Panel A), in MASC (Panel B) and its role in breast cancer (Panel C).

Figure 5 GCDPF-15/PIP expression in A. normal tissue from proteinatlas.com B expression in MASC from Skalova (2010)   C. role in breast cancer progression Naderi and Vanneste (2014)

Connecting biomarkers…  Debily and coworkers (2009)  identified  STAT5 through in silico promoter analyses of the genes co-modulated with GCDPF-15/PIP as a down stream transcription factor.

Stat5a

Signal transducer and activator of transcription 5A (Stat5a) and the Stat family of transcription are known as cellular mediators of response to cytokines and growth factors.  Phosphorylation leads to dimerization and nuclear import.

Phosphorylation of Stat5 leads to dimerization and nuclear import.

Figure 6  Stat5  Left The active Stat dimer undergoes nuclear import.  Right Nuclear Stat5a  from Skalova 2010

In their discussion, Skálová and coworkers mentioned the importance of Stat5a in mammary gland differentiation and growth.

Mammaglobin

Mammaglobin is a secretory protein with a molecular weight of 10.5 kDa that is overexpressed in breast carcinomas. The eosinophilic secreted material, in addition to being positive for PAS-D and mucin-4, is also positive for mammaglobin.

IHC image of Mammaglobin overexpressed in breast carcinomas. Right side panel is zoomed image of left panel.

Figure 7.  mammaglobin  from Skálová 2010.  Left  the original magnification  Right, a close up of the region in the box showing staining of secreted material

 

Foreshadowing of discovery the ETV6-NTRK3 fusion in secretory carcinomas of the skin, the authors mentioned mammaglobin expression in sweat gland tumors.

IHC in summary

Skálová and coworkers examined many more antigens than the ones they pictured in their 2010 report. The others were documented in Figure 1 of this landmark publication. Three different types of tumors were compared in Table 1

  1. newly recognized salivary gland mammary analog of secretory carcinoma (of the breast)
  2. secretory carcinoma of the breast
  3. acinic cell carcinoma of the salivary glands that over the years has been reclassified as MASC or just secretory carcinoma of the salivary glands
Table showing various IHC markers and their expression in various patient cases.

Table 1, modified, from Skálová   2010, Table 1

S100B can be categorized as a secreted protein as well as a binding partner of the tumor suppressor protein p53.

Vimentin and the listed cytokeratins are intermediate filament markers of cell lineage. Of note is that myoepithelial intermediate filament markers CK5/6 and CK14 were not detected.

GCDFP-15 /PIP and mammaglobin are secreted and may act in a autocrine or paracrine mode.

Note that epithelial membrane antigen (EMA) is another name for mucin 1.

Typical cancer driving growth factor binding tyrosine kinases are not detected in any of the three tumors. Myoepithelial markers are also not detected.

Molecular Features

Skálová and coworkers used rtPCR to amplify TEL-TrkC transcripts as well as an ETV6 break apart FISH assay to demonstrate  ETV6 gene disruption rearrangement. While some of the samples were not analyzable (NA) or not tested (NT), the obvious conclusion was that the authors had discovered a new type of salivary gland tumor. Other molecular controls not presented in Figure 5 of this  web page were presented in the original publication. In panel 5C yellow dots indicate intact ETV6 genes. Red and green dots indicate separation of the 5′ and 3′ ends of the ETV6 gene.

Fig. A, shows rtPCR to amplification of TEL-TrkC transcripts with ETV6 break apart FISH assay to demonstrate  ETV6 gene disruption rearrangement.

Figure 8 Molecular features of salivary gland secretory carcinoma A. PCR results targeting the junction of the Tel-TrkC transcript B. Sequencing results confirming the junction C. Break apart FISH results for the ETV6 gene The table is derived from Table 3 of the publication

In the years since this publication, MASC molecular diagnostics have become more sophisticated.

Important Information

Most of this discussion has focused on identifying a secretory carcinoma first noted in the breast in salivary glands. Being able to differentiate between salivary acinic cell carcinoma and secretory carcinoma expands treatment options. Secretory carcinomas are driven by constitutively active TrkC, acinic cell carcinomas are not. The former can be treated with a Trk inhibitor that is summarized in an easy to understand entrectinib video at the bottom of this page.

References

Debily MA, Marhomy SE, Boulanger V, Eveno E, Mariage-Samson R, Camarca A, Auffray C, Piatier-Tonneau D, Imbeaud S (2009). A functional and regulatory network associated with PIP expression in human breast cancer. PLoS ONE. 4 (3): e4696. PubMed

Hirokawa M, Sugihara K, Sai T, Monobe Y, Kudo H, Sano N, Sano T.(2002) Secretory carcinoma of the breast: a tumour analogous to salivary gland acinic cell carcinoma. Histopathology. 40. 223–229.  PubMed

Naderi A, Vanneste M (2014)Prolactin-Induced Protein Is Required for Cell Cycle Progression in Breast Cancer Neoplasia. 16(4): 329–342 PubMed

Skálová A, Vanecek T, Sima R, Laco J, Weinreb I, Perez-Ordonez B, Starek I, Geierova M, Simpson RH, Passador-Santos F, Ryska A, Leivo I, Kinkor Z, Michal M.(2010) Mammary analogue secretory carcinoma of salivary glands, containing the ETV6-NTRK3 fusion gene: a hitherto undescribed salivary gland tumor entity. Am J Surg Pathol. 34(5):599-608 PubMed