Original article The novel hormone INSL3 is expressed in human testicular Leydig cell tumors: A clinical and immunohistochemical study Marco Rossato, M.D., Ph.D. a, *, Ivan Matteo Tavolini, M.D. b , Alessandra Calcagno, Ph.D. a , Marina Gardiman, M.D. c , Fabrizio Dal Moro, M.D. d , Walter Artibani, M.D. d a Endocrine-Metabolic Unit, Clinica Medica 3, Department of Surgical and Medical Sciences, University of Padova, Padova, Italy b Department of Urology, Venice General Regional Hospital, Venice, Italy c Department of Pathology, University-Hospital of Padova, Padova, Italy d Department of Oncological and Surgical Sciences, Urology Clinic, University of Padova, Padova, Italy Received 23 September 2008; received in revised form 8 October 2008; accepted 9 October 2008 Abstract Insulin-like 3 (INSL3) is a novel peptidic hormone member of the relaxin-insulin-like family of peptide factors. It is almost exclusively produced by Leydig cells within the testis and participates to the complex mechanisms leading to physiological testicular descent during embryonic development. We performed a retrospective study evaluating clinical and histopathological characteristics of 13 patients surgically treated for testicular tumor and diagnosed to be affected by Leydig cell tumor (LCT). Furthermore, it was possible to retrieve the archived paraffin embedded tumor together with neighboring healthy testicular tissue of all subjects affected by LCT (12 benign and 1 malignant form), that were analyzed for INSL-3 expression. Immunohistochemical analysis of the tumor sections of the 13 patients affected by LCT demonstrated constitutive expression of INSL3 protein in all LCT, irrespective of the histological pattern of each LCT and with no significant differences of staining intensity between all tumors. In particular, no gross differences were evident between the staining for INSL3 in the 12 benign LCTs and the only one showing malignant clinical behavior. The present study shows that LCTs, a very rare form of testicular tumor with no proven specific serum and histological markers, express a novel member of the relaxin-insulin-like family of peptide factors previously identified as a secretory product of Leydig cells and named INSL3. Thus, there could be the possibility to evaluate the expression and secretion of this novel hormone as a marker of this rare testicular tumor. © 2009 Elsevier Inc. All rights reserved. Keywords: INSL3; Leydig cell tumor; Testicular cancer 1. Introduction Testicular cancer is the most common malignant neo- plasm in young men accounting for about 1% of cancer in the male [1] and with an overall incidence of 7.5 cases for 100,000 although with some differences between countries [2]. Since the majority of these tumors are curable, the mortality rate is low [3]. More than 90% of testicular tumors originate from germ cells [4], while stromal testicular tu- mors are very rare, representing less than 3% of all testicular neoplasm [5]. Among non-germ cell testicular tumors, those originating from Leydig cells are the most common type and although their natural history is benign, malignant cases of Leydig cell tumors (LCT) have been described, account- ing for about 10% of LCTs [5–7]. In 1993, a new member of the relaxin-insulin-like family of peptide factors was identified as a secretory product of Leydig cells and named insulin like 3 (INSL3) [8]. INSL3 represents one of the major secretory products of Leydig cells within the testis and participates, together with its receptor named relaxin family peptide 2 (RXFP2), in the complex mechanisms leading to the physiological testicular descent during embryonic development [9]. Mutations of INSL3 gene and/or its receptor have been implicated in the pathogenesis of some form of cryptorchidism, although these observations have been recently questioned [10 –12]. Since INSL3 is an exclusive product of Leydig cells, its presence is substantially restricted to men while women show very low plasma levels of this protein (at concentra- tions 10- to 12-fold lower than those of men) [13,14], * Corresponding author. Tel.: +39-49-8218747; fax: +39-49-8213332. E-mail address: marco.rossato@unipd.it (M. Rossato). Urologic Oncology: Seminars and Original Investigations xx (2009) xxx 1078-1439/09/$ – see front matter © 2009 Elsevier Inc. All rights reserved. doi:10.1016/j.urolonc.2008.10.015 ARTICLE IN PRESS