[542] Stem Cell Marker ALDH1 Expression in Melanoma

RN Tawil, Q Ahmed, P Sochacki, N Khouri, E Levi. Wayne State University School of Medicine, Detroit, MI; John D. Dingell VA Medical Center, Detroit, MI

Background: The issue of the expression of stem cell markers in melanoma is controversial. The recent publication of the aberrant expression of CD 20 in a subpopulation of melanoma-initiating cells also adds to the controversy (J Clin Oncol. 2008;26:2890-2894). Understanding and characterizing the various possible subpopulations within malignant melanoma and the dynamics of clonal dominance is currently being investigated to gauge the early and advanced characteristics of stem cell markers at these different stages. Aldehyde dehydrogenase-1 (ALDH1) has recently emerged as a possible marker for breast cancer, brain tumors and for identifying colonic stem cells in colorectal carcinoma. However, to our knowledge, ALDH1 has not been previously studied as a stem cell marker in melanoma.
Design: 35 patients were selected from a Veteran Administration Medical Center Hospital in Detroit, Michigan, with disease ranging from melanoma in situ, to nodular melanoma and metastatic melanoma. CD 20 and ALDH1 are two immunostains applied to the microslides prepared from paraffin-embedded tissue from these 35 patients.
Results: None of the cases (0/35, 0%) stained for CD 20. 20/35 cases (57%) stained moderately-to-diffusely for ALDH1 (staining 10-40% of the tumor cells). This group encompasses the patients with nodular and metastatic melanoma. 5/35 slides (14%) had focal-to-patchy staining for ALDH1, this group is comprised of the patients with early lesions (from melanoma in situ, up to Stage 1). Of these early lesions cases, 2/4 (50%) had subsequent advanced disease, or metastatic melanoma. 10/35 cases (29%) did not stain for ALDH1.
Conclusions: Our cases of melanoma do not show aberrant CD 20 expression, disproving the assumption of CD 20 as a marker for cancer stem cells in melanoma. However, ALDH1 was expressed in advanced melanoma, which translates to a higher percentage of melanoma cells being stem cell like. Fewer of the early lesions stained with ALDH1, but from the patient follow up of this group, 50% developed advanced disease. Therefore, ALDH1 can potentially be used as a prognostic stem cell marker to predict metastatic melanoma in early lesions.
Category: Dermatopathology

Monday, March 22, 2010 9:30 AM

Poster Session I Stowell-Orbison/Surgical Pathology/Autopsy Awards Poster Session # 76, Monday Morning

 

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