[1255] Immunohistochemical Expression of CD117 (C-Kit) in Mucosal Melanomas of the Head and Neck

RS Shibata, F Martiniuk, Y Qian, HG Liu, H Yee, W Levis, BY Wang. New York University School of Medicine, New York, NY; Tong Ren Hospital, Beijing, China

Background: Mucosal Melanomas of the head and neck region are rare and account for 1.3% of all cutaneous and non-cutaneous melanomas. Treatments often require adjuvant radiation and/or chemotherapy, due to difficulty to completely remove those tumors by surgery alone. Recent studies showed c-kit gene mutation in skin and mucosal melanomas, suggesting the therapeutic benefit of tyrosine kinase inhibitors, such as imatinib (Gleevac). We have applied immunohistochmistry on c-kit protein and demonstrated c-kit immunoreactivity in mucosal melanomas.
Design: Twenty seven patients with mucosal melanomas from nasal cavities and para sinuses were treated in 2 major tertiary hospitals. All cases were diagnosed as primary mucosal melanomas and were confirmed by immunostains for melanocytic markers including S100 protein, HMB-45, PNL-2, and/or Melan-A and PNL-2Melan-A. 27 cases of formalin fixed and paraffin embedded samples were retrieved from 2 hospital archives. Automated Iimmunohistochemistry was performed using a pre-diluted monoclonal c-kit antibody (Clone 9.7, Ventana Medical SysytemsSystems, Tucson, AZ), by a standard avidin-biotin complex detection using the immunostainers BenchMark XT (Ventana Medical SysytemsSystems, Tucson, AZ). Internal positive (mast cells) and negative controls were identified in every stained section.
Results: Immunohistochemical expression of c-kit was determined by evaluating the membranous staining using a semi-quantitative measurement as follows: 1+ for < 25% of tumor cells, 2+ for 25-50%, 3+ for > 50+, and 4+ for > 75% of cells displaying positive staining. We found that 24 of the 27 (88 %) tumors had distinct positive membranous staining. Among those positive cases, 5 tumors were uniformly diffusely positive (4+, > 75%), 8 were strongly positive (3+, > 50%), 7 were patchy positive (2+, > 25-50 %), and 4 showed focal and weak (1+, < 25 %) staining.
Conclusions: Our results show that immunoreactivity of CD117 (c-kit) can be detected in majority of mucosal melanomas with a distinct, reproducable membranous staining pattern. Immunohistochemical expression of c-kit may be useful to provide a potential therapeutic target using tyrosine kinase inhibitors to treat mucosal melanomas.
Category: Head & Neck

Monday, March 22, 2010 9:30 AM

Poster Session I Stowell-Orbison/Surgical Pathology/Autopsy Awards Poster Session # 172, Monday Morning

 

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