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Diagnostic Utility of Novel Stem Cell Markers SALL4, OCT4, NANOG, SOX2, UTF1, and TCL1 in Primary Mediastinal Germ Cell Tumors

Liu, Aijun, MD*; Cheng, Liang, MD; Du, Jun, MD; Peng, Yan, MD, PhD§; Allan, Robert W., MD; Wei, Lixin, MD*; Li, Jianping, BS; Cao, Dengfeng, MD, PhD

The American Journal of Surgical Pathology: May 2010 - Volume 34 - Issue 5 - p 697-706
doi: 10.1097/PAS.0b013e3181db84aa
Original Articles
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Primary mediastinal germ cell tumors (GCTs) are rare and sometimes they pose diagnostic difficulty without immunohistochemical studies. Here, we investigated the diagnostic utility of 6 stem cell markers (SCMs) SALL4, OCT4, NANOG, SOX2, UTF1, and TCL1 in 16 primary mediastinal seminomas, 3 embryonal carcinomas (ECs), 10 yolk sac tumors (YSTs), 7 teratomas (4 mature, 3 immature), and 1 choriocarcinoma. The percentage of tumor cells stained was scored as: 0 (no tumor cell staining), 1+ (≤30%), 2+ (31% to 60%), 3+ (61% to 90%), and 4+ (>90%). The staining intensity of SCMs was scored as weak, moderate, or strong. We also compared them with currently used GCT markers placental-like alkaline phosphatase (PLAP), α-fetoprotein (AFP), c-KIT, CD30, and glypican-3. All 16 seminomas showed staining for SALL4 (4+ in 15, 2+ in 1) (15 strong, 1 moderate), OCT4 (4+ in 11, 3+ in 4, 2+ in 1) (13 strong, 3 moderate), and UTF1 (4+ in 13, 3+ in 2, 2+ in 1) (7 strong, 5 moderate, 4 weak). Positive staining was shown by 9/9 seminomas tested for NANOG (4+ in 7, 2+ in 2) (8 strong, 1 weak), TCL1 (4+ strong in all), c-KIT (4+ in all), and PLAP (4+ in 5, 3+ in 1, 2+ in 2, 1+ in 1), but SOX2 staining was negative in all these tumors. All 3 ECs showed 4+ strong staining for SALL4, OCT4, and UTF1 but negative for TCL1. SOX2 staining was seen in 3/3 ECs (4+ strong in 1, 3+ weak to moderate in 2) whereas NANOG staining was seen in 2/3 ECs (2+ weak, 1+ moderate). CD30 staining was seen in 3/3 ECs (1+, 2+, 4+). Strong SALL4 staining was seen in 10/10 YSTs (4+ in 9, 2+ in 1). All 10 YSTs showed AFP (1+ in 7, 2+ in 1, 3+ in 2) and glypican-3 (1+ in 3, 2+ in 1, 3+ in 5, 4+ in 1) staining but only 4/10 YSTs showed PLAP staining (1+ in all 4). The mean percentage of YST cells stained with SALL4 was 92%, whereas it was 23% for AFP, 50% for glypican-3, and 4% for PLAP (P<0.01). Focal (1+) SALL4 (weak) and SOX2 (weak to moderate) staining was seen in 2/7 and 4/7 teratomas, respectively. The choriocarcinoma was negative for all 6 SCMs. Eleven thymomas and 6 thymic carcinomas were negative for 6 SCMs. No staining of NANOG and SOX2 was seen in 20 lymphomas (5 Hodgkin, 5 large B cell, 5 lymphoblastic, 5 anaplastic large cell) (other 4 SCMs in lymphomas earlier studied). Our study indicates that SALL4, OCT4, NANOG, SOX2, UTF1, and TLC1 are novel sensitive diagnostic markers for primary mediastinal GCTs, with high specificity. Of these 6 SCMs, SALL4 is the only 1 expressed in YST. These novel SCMs are more sensitive than the currently used markers for mediastinal GCTs.

*Department of Pathology, The Chinese PLA General Hospital

Department of Pathology, Beijing Hospital, Beijing, China

Department of Pathology and Laboratory Medicine, Indiana University, Indianapolis, IN

§Department of Pathology, The University of Texas-Southwestern Medical Center at Dallas, Texas

Department of Pathology and Laboratory Medicine, The University of Florida, Gainesville, FL

Department of Pathology and Immunology, Washington University School of Medicine, St Louis, MO

Correspondence: Dengfeng Cao, MD, PhD, The Lauren V. Ackerman Laboratory of Surgical Pathology, Division of Anatomic and Molecular Pathology, Washington University School of Medicine, 660 S Euclid Avenue, Campus Box 8118, Saint Louis, MO 63110 (e-mail: dcao@path.wustl.edu).

© 2010 Lippincott Williams & Wilkins, Inc.