[1341] Expression of PAX2 and Renal Cell Carcinoma Antigen in Mucoepidermoid Carcinoma

Bo Xu, Richard T Cheney, Angela Omilian, Yuguang Liu, Carl Morrison. Roswell Park Cancer Institute, Buffalo, NY; State University of New York at Buffalo, Buffalo, NY

Background: Mucoepidermoid carcinoma (MEC) is the most common malignant tumor of salivary origin. It is a heterogeneous neoplasm in which clear cells account about 10-60% in most of MEC. Clear cell renal cell carcinoma (CCRCC) is the most common metastatic clear cell tumor in head and neck. The distinction between MEC with clear cells (CMEC) and metastatic CCRCC can be challenge in a small biopsy specimen. The aim of this study is to evaluate the utility of expression of PAX2 and RCCma between CMEC and metastatic CCRCC in a clinical setting.
Design: Twenty-three cases of MEC and ninty-four cases of metastatic RCC were identified from Roswell Park Cancer Institute (RPCI) pathology archives from 2000 to 2010 for TMA construction. Among MECs, 11 are of major salivary gland origin (parotid and submaxillary glands), 11 of minor salivary gland origin, and 1 involving a cervical lymph node. Immunostains on TMA sections were carried out according to manufacturer's protocols. This study was approved by Institution Review Board at RPCI.
Results: The 23 cases of MEC were classified according to the criteria by WHO as low grade (14 cases, 61%), intermediate grade (5 case, 22%) and high grade (4 case, 17%). Eleven cases (48%) show variable clear cell component (CMEC), ranging from 20-60% of the tumor. Majority CMEC were low grade (82%). RCCma was positive in 3/11 CMEC (13%) with variable degree of membranous and cytoplasmic staining. All of these cases were low grade. Positive immunoreactivity for PAX2 was found in 21 cases (91%) showing diffuse cytoplasmic reactivity. However, no cases showed nuclear staining that is specific for PAX2. In metatstaic RCC, the nuclear staining for PAX2 was demonstrated in 21 of 94 cases (22%) and the membranous staining for RCCma was found in 19 cases (20%). In six cases of metastatic RCC to the head and neck, only two cases were positive either for PAX2 or RCCma. Three cases that metastasize to salivary glands and thyroid were negative for PAX2 and RCCma.
Conclusions: In this study, expression of RCCma was found in a small subset of MEC. These findings have not been reported previously. Caution should be made when one interprets positive RCCma and PAX2 immunostaining results on work-up for differential diagnosis between CMEC and metastatic CCRCC. Clinicopathologic correlation combined with histomorphology and a panel of immunohistochemical markers are essential to render correct diagnosis.
Category: Head & Neck

Tuesday, March 20, 2012 1:00 PM

Poster Session IV # 155, Tuesday Afternoon


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