70 Surgery alone Negative margins Low grade histology High grade histology Low risk (non angioinvasive, High risk (highly inﬁltrative) non inﬁltrative) histologic histologic subtype subtype Low T stage (T1 or T2) High T stage (T3 or T4) pN? Perineural invasiona Table 1 General categories of management of primary salivary gland carcinomas [3] Surgery and radiotherapy Additional neck dissection Close (\2 mm) or positive margins All cN? cN0 but high grade histology cN0 but high risk (angioinvasive) histologic subtype cN0 but high T stage (T3 or T4) Head and Neck Pathol (2009) 3:69–77 Systemic chemotherapy Metastatic or unresectable disease T = tumor stage in TNM classiﬁcation, cN? = clinically node positive, cN0 = clinically node negative, pN? = pathologically node positive a Somewhat controversial depending on tumor type histologic grading as applied to salivary gland carcinomas in general and with respect to select common tumor types. Discussion General Grading of Salivary Gland Carcinomas The ideal requirements for any grading system are as follows: • • • • • • Accurately predicts outcome Can be used to stratify patients into distinct manage- ment categories Applicable to all sites in which a tumor can be seen Simple criteria Quick and time efﬁcient Reproducible with minimal inter and intraobserver variability. Practically speaking, this ideal is difﬁcult or even impossible to achieve in salivary gland carcinomas mainly because of the lack of sufﬁcient sample size to devise statistically valid systems that fulﬁll the aforementioned criteria. Meta analyses hold very little meaning since grading of salivary gland carcinomas is not standardized. Most grading is done ‘intuitively’ using general cytomor- phologic features (pleomorphism, mitoses, necrosis) and is thus highly individualized. Even when grading systems exist, there may be several to address the same tumor type, none of which correlate exactly with one another. Despite these obstacles, using the data available, as well as good clinical acumen, the various tumor types can at least be stratiﬁed into a meaningful working stratiﬁcation scheme that can be used to parse tumors into those that do not require treatment beyond excision (i.e. low risk) of primary tumor and those that do (i.e. high risk). Table 2 divides all entities listed in WHO classiﬁcation scheme into low risk and high risk categories. Histologic grading will additionally split certain tumor types (i.e. mucoepidermoid carcinoma) between both risk categories. Is grading of salivary gland tumors always necessary? The answer is no. Many tumor types are for the most part deﬁnitionally high risk both histologically and biologically (i.e. conventional salivary duct carcinoma, squamous cell carcinoma, small cell neuroendocrine carcinoma) or low risk (i.e. epithelial-myoepithelial carcinoma, polymorphous low grade adenocarcinoma). The caveat is that high grade versions of ‘intrinsically’ low grade tumors do exist as do low grade versions of typically high grade tumors. Both pathologists and clinicians need to be aware of these variants. Thus: • • The usual example of such a tumor type may not need to be qualiﬁed with a grading descriptor. An unusually high or low grade variant of a tumor should be conveyed in the pathologic report. Perhaps the most relevant example of this phenomenon is with carcinoma ex pleomorphic adenoma. Historically and even currently in the clinical literature, [2–4] carci- noma ex pleomorphic adenoma is automatically considered a high grade malignancy. In most cases, this is true with high grade adenocarcinoma, not otherwise speciﬁed (NOS), and salivary duct carcinoma being the most com- mon histologic subtype of the carcinomatous component. However, as many as 15% of tumors are low grade and may behave in a more indolent fashion [5]. More recently, there is evidence to suggest that ‘intracapsular’ carcinoma ex pleomorphic adenoma and minimally invasive carci- noma (\1.5 mm of invasion) ex pleomorphic adenoma (Fig. 1) are also indolent variants that should not be con- sidered equivalent to the typical carcinoma ex pleomorphic adenoma.