Salivary duct carcinoma: cytokeratin 14 as a marker of in-situ intraductal growth

Histological, immunohistological and molecular characteristics of intraductal precursor of carcinoma ex pleomorphic adenoma support a multistep carcinogenic process

In recent years, multistep carcinogenesis of carcinoma ex pleomorphic adenoma (CEPA) has been identified, starting with intraductal neoplasia within pre-existent pleomorphic adenoma (PA). However, as yet there is no consensus regarding clinical relevance and appropriate terminology of precursor lesions in CEPA. We therefore decided to investigate precursor lesions, especially intraductal carcinoma, in a series of 85 cases of CEPA. Intraductal carcinoma confined by benign myoepithelial cells was found in 60 cases and mostly exhibited high-grade cellular atypia, increased cellular proliferation and frequent genetic alterations (TP53, Her2-neu, androgen receptor). Intraductal carcinoma was absent only in the myoepithelial type of CEPA. In 26 cases, purely intraductal CEPA with extensive intraductal expansion was found. This suggests that there is a long period of intraductal growth before extraductal intracapsular infiltration of the PA. We identified two different histomorphological types of intraductal carcinoma, which we call 'clinging' and 'solid' types. In summary, combined histological, immunohistological and molecular data strongly support multistep carcinogenesis starting with intraductal carcinoma for all non-myoepithelial types of CEPA. The clinical significance of our finding of two histomorphological types of intraductal carcinoma (clinging and solid) is not yet clear. Intraductal carcinoma, intracapsular invasive CEPA and minor extracapsular invasive CEPA (up to about 6 mm) all show favourable prognosis and together comprise half of the cases in our study.

Salivary duct carcinomas can be classified into luminal androgen receptor-positive, HER2 and basal-like phenotypes

AIMS

The aim of this study was to devise a molecular classification for salivary duct carcinomas (SDCs) based on the similarities between SDCs and breast carcinomas and on characteristics of the microarray-based gene expression profiling-defined molecular subtypes of breast cancer.

METHODS AND RESULTS

Forty-two pure salivary duct carcinomas, 35 of which contained an in-situ component as defined by histological review and/or immunohistochemical analysis, were stained with antibodies for oestrogen receptor (ER), progesterone receptor (PR), androgen receptor (AR), human epidermal growth factor receptor 2 (HER2), epidermal growth factor receptor (EGFR) and cytokeratin (CK) 5/6. Based on these markers, tumours were classified into HER2, luminal androgen receptor-positive, basal-like, luminal and indeterminate phenotype. Analysis revealed that 16.7%, 69%, 4.8%, 9.5% and 0% were of HER2, luminal androgen receptor-positive, basal-like, indeterminate and luminal phenotype, respectively. The in-situ and invasive components displayed the same molecular subtype in all but one case.

CONCLUSION

Salivary duct carcinomas can be classified into molecular subgroups approximately equivalent to those in the breast. We also report on the existence of a subgroup of bona fide pure salivary duct carcinomas that have a 'basal-like' phenotype. Understanding the phenotypic complexity of SDCs may help to expedite the identification of novel therapeutic targets for these aggressive tumours.

Salivary duct carcinoma: new developments--morphological variants including pure in situ high grade lesions; proposed molecular classification

Salivary duct carcinoma (SDC) is an aggressive primary salivary malignancy which microscopically resembles high-grade ductal carcinoma of the breast, with both in situ and invasive patterns. It is typically found in older men, most often in the parotid. It can arise de novo or as the malignant component of carcinoma ex pleomorphic adenoma. SDC is generally a hematoxylin and eosin stain-based diagnosis, with special stains and immunohistochemistry acting mainly in a confirmatory role. Other than epithelial markers, SDC expresses androgen receptors in most cases, with true HER2 positivity seen in about 15 %. Based on these data and analogous to similar schemes in the breast, it is suggested that SDCs can be classified into three main groups: luminal androgen receptor positive, HER2+ and basal phenotype. This may form the basis for prognostic information and new therapeutic possibilities. In addition to the usual type of SDC, a few less common morphological variants have been reported: papillary, micropapillary, mucin-rich, sarcomatoid and oncocytic, as well as pure in situ cases.

An analysis of PLAG1 and HMGA2 rearrangements in salivary duct carcinoma and examination of the role of precursor lesions

AIMS

Salivary duct carcinoma (SDC) often arises in pleomorphic adenoma (PA). Putative precursors, including low-grade cribriform cystadenocarcinoma (LGCCC) and ductal carcinoma in-situ (DCIS), are more controversial. Rearrangement of PLAG1 or HMGA2 is seen in 50-70% of PAs, but this has not been investigated in SDC. Using a large collection of SDCs from a single institution, we aimed to study these genes by fluorescence in-situ hybridization (FISH), and to correlate the presence of precursor lesions/intraductal proliferations with gene alterations.

METHODS AND RESULTS

Forty-four SDCs were stained for smooth muscle actin, CK14, and p63, and examined with PLAG1 and HMGA2 FISH. Eight cases were SDC ex-PA; ten had a hyalinized nodule (HN), which is suspicious for PA; six arose in association with LGCCC; and twenty were 'de-novo' SDCs. Ten cases had PLAG1 rearrangement/amplification (22.7%) and eight had HMGA2 (18.2%) rearrangement/amplification. The positive cases were four SDC ex-PAs, eight SDCs with an HN, and five 'de-novo' SDCs. Twenty-three SDC ex-PAs were present in total (52.3%). All six SDC ex-LGCCCs were FISH-negative. Myoepithelial staining surrounded all LGCCCs, and demonstrated DCIS in 17 cases. Eleven DCIS lesions were in SDC ex-PAs or FISH-positive 'de-novo' SDCs. These cases represent 'cancerization' of ducts. Only six FISH-negative 'de-novo' SDCs showed DCIS.

CONCLUSIONS

A large proportion of SDCs arise in PAs (with or without residual evidence of a PA). A small proportion of SDCs arise in LGCCCs. Cases showing DCIS often represent cancerization.

Common Malignant Salivary Gland Epithelial Tumors

Malignant salivary gland epithelial tumors are histologically diverse with at least 24 recognized distinct entities. In general, malignant tumors account for 15% to 30% of parotid tumors, 40% to 45% of submandibular tumors, 70% to 90% of sublingual tumors, and 50% of minor salivary tumors. Common malignancies include mucoepidermoid carcinoma, adenoid cystic carcinoma, acinic cell carcinoma, salivary duct carcinoma, carcinoma ex pleomorphic adenoma, polymorphous lowgrade adenocarcinoma, and myoepithelial carcinoma. Each tumor type has its own unique histologic variants and prognostic pathologic features, and only mucoepidermoid carcinomas have a formalized grading system. The molecular pathogenesis of certain tumors, such as mucoepidermoid carcinoma and adenoid cystic carcinoma, has recently begun to be elucidated.

Intraductal carcinoma of salivary gland (so-called low-grade cribriform cystadenocarcinoma) arising in an intraparotid lymph node

Since the first description of an entirely intraductal epithelial proliferation of salivary gland by Chen in 1983 as an "intraductal carcinoma", there have been several dozen reported cases with the same and various additional names including "low-grade salivary duct carcinoma", "low-grade cribriform cystadenocarcinoma" and "carcinoma in situ" of salivary gland. These refer to a combination of nests and cysts of varying size formed by a cellular proliferation resembling atypical ductal hyperplasia or ductal carcinoma in situ of the breast. The lesions are generally entirely intraductal with low, intermediate or high-grade dysplasia. Occasional benign tumors of salivary gland, particularly Warthin tumor and rare salivary carcinomas may arise within an intraparotid lymph node. In addition, intraparotid lymph nodes are a routine location for metastatic disease. A case of a 59-year-old female with a parotid mass is described, which grossly had the appearance of a Warthin tumor. Microscopically, it was an entirely intranodal proliferation of cells with diffuse AE1/AE3 and S100 positivity. The nests and cysts were completely surrounded by a rim of non-neoplastic myoepithelial cells, which were positive for CK14, p63, SMA, MSA and calponin. The tumor cells were negative for these markers. The cells were only focally positive for AR and BRST-2. They showed negligible MIB-1 staining. This report describes, for the first time, an entirely intranodal location for a low-grade intraductal carcinoma (so-called low-grade cribriform cystadenocarcinoma).

Intraductal carcinoma is the precursor of carcinoma ex pleomorphic adenoma and is often associated with dysfunctional p53

AIMS

Although intraductal carcinoma has been demonstrated in intracapsular carcinoma ex pleomorphic adenoma (CEPA), the morphological and genetic stages of transformation of pleomorphic adenoma (PA) to CEPA are not fully understood. The aim of this study was to investigate the morphology of intracapsular CEPA.

METHODS AND RESULTS

The largest series of intracapsular CEPA studied was subject to immunohistochemical double-staining to detect p53 protein and cellular proliferation in different types of cell combined with mutational analysis of the p53 gene in laser-microdissected material. Intraductal carcinoma with high-grade cellular atypia and frequent accumulation of p53 protein was found in 15/19 cases. Purely intraductal carcinoma was found in eight cases. Mutation of p53 was found in 7/19 cases, of which it was found in intraductal carcinoma in 5/15 cases.

CONCLUSIONS

The frequent demonstration of intraductal carcinoma indicates that this preinvasive lesion is likely to be a constant feature in the malignant transformation of PA to CEPA. It appears to be a feature of CEPA developing from both primary and recurrent PA. The combined immunohistochemical and genetic data show that 14/19 cases of CEPA and 11/15 cases with intraductal carcinoma showed genetic or morphological evidence of dysfunctional p53, indicating that this is an early event in malignant transformation.

Low-grade Intraductal Carcinoma of Salivary Gland

Low-grade intraductal carcinomas (LG-IDCs) of salivary gland are rare neoplasms that resemble atypical ductal hyperplasia or LG-IDCs of the breast. They have been referred to as "low-grade salivary duct carcinomas" or "low-grade cribriform cystadenocarcinomas." Herein, we describe 3 additional cases of LG-IDCs, 2 were pure intraductal carcinomas, although 1 demonstrated increasing cytologic atypia and progression to an invasive adenosquamous carcinoma. The latter had been present for 7 years before demonstrating clinical and pathologic progression to a widely invasive malignancy. The intraductal component in all cases exhibited a remarkable degree of apocrine differentiation. The tumor cells were positive for AE1:AE3, Cam 5.2, high molecular weight keratin, CK7, CK19, BRST-2, and androgen receptors (ARs). S-100 was positive in 2 cases and negative in 1 case. The intraductal neoplastic cells were surrounded by myoepithelial cells positive for CK14, actins, calponin, high molecular weight keratin, and p63. All the tumors were negative for CK20, estrogen and progesterone receptors, Her2Neu, and p53. Extensive apocrine differentiation, expression of ARs, CK7, and CK19, and progression to a widely invasive carcinoma after a long clinical latency have not been reported in LG-IDCs previously. These tumors share some histopathologic features with salivary duct carcinoma including apocrine differentiation, and expression of ARs and BRST-2. The terms "low-grade salivary duct carcinomas" and "low-grade cribriform cystadenocarcinomas" should be abandoned in favor of LG-IDC of salivary gland, which better reflects their predominantly noninvasive, intraductal nature.

Preinvasive intraductal neoplasia in salivary adenocarcinoma, not otherwise specified

Preinvasive intraductal neoplasia of the salivary glands has only been identified in the rare salivary-duct carcinoma, whereas, it is an established feature of carcinomas of other glands. A fortuitous observation of what appeared to be intraductal tumor in a salivary adenocarcinoma, not otherwise specified, led to the present investigation to determine whether intraductal neoplasia is a significant feature of this carcinoma. Intraductal tumor confined by normal CK14-positive, actin-negative ductal basal cells was identified in 15 of 22 cases (68%). The degree of cellular atypia and the pattern of growth of intraductal tumor was similar to that of the invasive tumor. Cases with intraductal tumor devoid of invasive tumor were not found. Intraductal tumor is identified as the pre-invasive precursor of adenocarcinoma, not otherwise specified, and apparently develops in excretory ducts. The findings support the possibility that different salivary tumors arise from different types of parenchymal cell. Possibly intraductal neoplasia is a universal feature of many types of salivary tumor, but has been overlooked because of the need to use immunohistology to demonstrate it and because it may no longer be present as such when the tumor presents as a clinical lesion.

Immunohistochemical expression of cytokeratins 7 and 20 in malignant salivary gland tumors

On the basis of the heterogeneity of cytokeratins 7 and 20 expression in malignant epithelial tumors, the cytokeratin 7/20 immunophenotype has served as a useful diagnostic tool for discrimination of primary and/or metastatic carcinomas of unknown origin. However, the expression pattern of these cytokeratins in malignant salivary gland tumors has not been thoroughly studied. Our study material was composed of 84 malignant tumors of primary major or minor salivary gland origin. Nine histologic types of carcinoma were represented, including mucoepidermoid (26 cases), adenoid cystic (25), polymorphous low grade (11), salivary duct (8), acinic cell (4), ex mixed tumor (3), not otherwise specified (3), clear cell (2), and basal cell (2). In all, 13 cases of primary skin or mucosal squamous cell carcinoma with secondary salivary gland involvement were also examined. Immunoreactivity for cytokeratin 7 was evident in all malignant salivary gland tumors; the staining pattern was diffuse and strong in 62 cases, and focal and strong in 22 cases. In contrast, 78 cases were negative for cytokeratin 20, whereas only six cases (two mucoepidermoid, one adenoid cystic, and three salivary duct) displayed focal weak positivity. Overall, 92.9% of malignant salivary gland tumors were characterized by a cytokeratin 7 positive/20 negative immunoprofile, the remaining 7.1% of cases being positive for both cytokeratins. The latter phenotype was more common in salivary duct carcinomas (P< or =0.05). On the other hand, most squamous cell carcinomas (69%) were negative for both cytokeratins, while the remaining cases (31%) were negative for cytokeratin 20 and focally weakly positive for cytokeratin 7. We suggest that assessment of cytokeratin 7/20 immunoprofile may facilitate the differential diagnosis of (a) primary malignant salivary gland tumors from metastatic tumors, (b) metastatic salivary gland tumors, (c) primary salivary gland tumors, especially mucoepidermoid carcinomas, from squamous cell carcinomas, and (d) salivary duct carcinomas from other malignant salivary gland tumors.

Salivary duct carcinoma: immunohistochemical profile of an aggressive salivary gland tumour

BACKGROUND

Salivary duct carcinoma (SDC) is considered to be a distinct malignancy of the major salivary glands, because of its highly aggressive behaviour, and the high rate of recurrence, metastasis, and disease related death.

AIMS

To investigate expression of the proteins involved in the retinoblastoma (pRb) and p53 pathways, which control cell cycle progression at the G1/S checkpoint, and also expression of the c-erbB-2 oncoprotein in SDCs.

METHODS

Using a streptavidin-biotin method, five cases of SDC were evaluated immunohistochemically for the presence of cyclin D1, CDK4 (cyclin dependent kinase 4), p16 (CDK2A), pRb (retinoblastoma protein), E2F-1, p53, mdm2 (murine double minute 2), bcl-2, and the c-erbB-2 oncoprotein to determine whether there was a correlation between the expression of these proteins and patient outcome.

RESULTS

All of the cases showed deregulation of the pRb and p53 pathways. Of the five patients analysed, only the patient with longterm survival (10 years) was not positive for c-erbB-2 expression.

CONCLUSIONS

c-erbB-2 overexpression was associated with a poor prognosis. Aggressive behaviour, recurrence, and metastatic potential do not appear to be related to cell cycle deregulation, but seem to be associated with the c-erbB-2 oncoprotein, which is involved in matrix degradation and proteolitic activity, in addition to increases in vessel permeability, endothelial cell growth, proliferation, migration, and differentiation. There was a correlation between c-erbB-2 oncoprotein expression and aggressive behaviour in SDCs.