[1285] Utility of Androgen Receptor, Her-2/Neu, Cytokeratin 5/6 and p63 Immunostaining in Distinguishing Salivary Duct Carcinoma from High Grade Mucoepidermoid Carcinoma

Randall T Butler, Serena Byrd, Matthew E Spector, Jonathan B McHugh. University of Michigan, Ann Arbor, MI

Background: Salivary duct carcinoma (SDC) can be misdiagnosed as high-grade mucoepidermoid carcinoma (MEC) (1). Distinguishing SDC from MEC is important as the former group of tumors is typically more clinically aggressive with poor 5-year survival rates. In addition, given high rates of androgen receptor (AR) positivity and Her-2/neu overexpression and amplification in SDC, targeted therapies are indicated in some patients. No systematic studies looking at immunohistochemical markers to distinguish these two entities have been performed.
Design: 48 cases of salivary duct carcinoma diagnosed at our institution were used to build a tissue microarray (TMA). This array, as well as a MEC TMA containing 81 carcinomas, including 9 high-grade tumors, were stained with antibodies to AR, Her-2/neu, p63, CK 5/6 and k903 (34βE12). The results of immunostaining (except for Her-2/neu) were scored with a modified Allred score, utilizing intensity and percentage of tumor staining. Her-2/neu results were reported using an established scoring system. Sensitivity, specificity, positive predictive value (PPV) and negative predictive values (NPV) were calculated.
Results: Cytokeratin k903 was not helpful in distinguishing SDC from MEC as 84% and 98% were positive, respectively. AR and Her-2/neu positivity were specific for SDC (Table 1). In contrast, p63 and CK 5/6 were specific for MEC including the high grade MECs (Table 2). Three MECs that were negative or had only focal staining were low grade cystic and mucous cell rich and would not be confused with SDC.

SDC marker performance

	Sens (%)	Spec (%)	PPV (%)	NPV (%)
AR	57	100	100	75
Her-2/neu	22	100	100	69

MEC marker performance

	Sens (%)	Spec (%)	PPV (%)	NPV (%)
p63	97	85	89	95
CK 5/6	84	65	75	76

Conclusions: A panel of AR, Her-2/neu, p63 and CK 5/6 is helpful in distinguishing SDC from high grade MEC in cases where histologic overlap exists. This distinction is important as SDC is a highly aggressive malignancy with most patients dying of disease within 4 years of diagnosis. In addition, targeted therapies such as androgen deprivation and/or Herceptin may be indicated in SDC.
1. Chevevert, Jacinthe, Leon E. Barnes, and Simion J. Chiosea. Mucoepidermoid Carcinoma: A Five-Decade Journey. Virchows Arch. 2011;458:133-140.
Category: Head & Neck

Tuesday, March 20, 2012 1:00 PM

Poster Session IV # 153, Tuesday Afternoon