CYTOGENETICS OF A MALIGNANT OVARIAN GERM-CELL TUMOR Jannie VAN ECHTEN 1 *, Lena C. VAN DOORN 2 , Hans C. VAN DER LINDEN 3 , Anneke Y. VAN DER V EEN 1 , Curt W. BURGER 2 and Bauke DE JONG 1 1 Department of Medical Genetics, University of Groningen, Groningen, The Netherlands 2 Department of Obstetrics and Gynaecology, Vrije Universiteit, Amsterdam, The Netherlands 3 Department of Pathology, Vrije Universiteit, Amsterdam, The Netherlands Cytogenetic investigation of a malignant ovarian tumor diagnosed as a mixed germ-cell tumor, composed of exten- sive choriocarcinoma and foci of yolk-sac tumor, revealed a highly abnormal chromosomal pattern. W e found a chromo- some number in the hypertriploid/hypotetraploid range, and several clonal structural abnormalities, including 2 copies of an isochromosome 12p. W e showed that the chromosomal pattern of this ovarian tumor is very similar to that of testicular germ-cell tumors. This finding, together with re- ported cytogenetic data of malignant ovarian germ-cell tu- mors, supports the hypothesis that ovarian and testicular germ-cell tumors are strongly related entities that may have a similar origin and pathogenetic pathway. Int. J. Cancer 77:217–218, 1998.  1998 Wiley-Liss, Inc. About 15 to 20% of all ovarian neoplasms are germ-cell tumors (GCTs), of which the majority are benign cystic teratomas. Malignant ovarian GCTs (OGCTs) are found principally in children and young adults. Malignant OGCTs and testicular GCTs (TGCTs) are histologically similar, and are thought to have a common pathogenesis. Malignant OGCTs may be composed solely of dysgerminoma, the ovarian counterpart of testicular seminoma, yolk-sac tumor, choriocarcinoma, embryonal carcinoma and tera- toma, or they may be composed of a mixture of the different histological components, resulting in a mixed OGCT (Crum, 1994). In this report we present the cytogenetics of a malignant mixed OGCT. The chromosomal pattern was compared with our cytogenetic data of TGCTs and with reported cytogenetic data of malignant OGCTs, in order to shed light on the pathogenesis of GCTs. MATERIAL AND METHODS Case history In a 27-year-old woman an unremarkable routine diagnostic laparoscopy was performed in her work-up for primary infertility. Within a month she presented with irregular bleedings. Ultrasonog- raphy revealed a 6-cm cystic mass on the right side of the uterus. The urine pregnancy test was positive. Serum alpha-1-feto-proteine and beta-human chorionic gonadotrophin levels were elevated; 1798 μg/l (normal 5 μg/l) and 1600 U/l (normal 5 U/l) respec- tively. At laparotomy, a 7-cm enlarged right ovary was removed and a staging procedure was performed. Histological examination of the tumor showed extensive choriocarcinoma and foci of yolk-sac tumor, which is consistent with a malignant mixed OGCT. Methods A fresh representative sample of the tumor was submitted for cytogenetic investigation. Part of the tumor sample was processed for direct harvesting. Briefly, the tissue was mechanically disaggre- gated, using scalpels, and half of the disaggregated tissue was directly incubated for at least 30 min (room temperature) with 0.05 μg/ml colcemid, while the other half was incubated for 3.5 and 18 hr (37°C, 5% CO 2 ) with collagenase type II (500 U/ml and 250 U/ml respectively) and colcemid (0.05 μg/ml and 0.01 μg/ml respectively). Short-term culturing was performed on the remain- ing part of the tumor sample. The tissue was mechanically and enzymatically disaggregated using scalpels and collagenase type II, 250 U/ml, and DNase, 0.002%. The cells were cultured for 5 days (37°C, 5% CO 2 ) in RPMI 1640, supplemented with 13.5% FCS, glutamine and antibiotics. Chromosome preparations were made after direct harvesting and short-term culturing, using standard cytogenetic techniques. The chromosomes were G-banded using pancreatin, 0.1%, and Giemsa, and the karyotypes were described according to the ISCN (1995). FISH was performed on metaphase preparations with biotin- labelled DNA of M28 (a mouse-human somatic hybrid cell line with an i(12p) chromosome as the only human material) and CEPH YAC 958B8 (YAC at 12pter), using standard techniques (Taanman et al., 1991). RESULTS We analyzed 19 metaphases (18 from the direct-harvesting method and 1 from the short-term culture) with the following modal composite karyotype: 77D883n,XXX,+del(1)(q23) [8],+del(1)(p11)[2],+2,add(3)(p11)[7],+idic(3)(p14)[10],+7,+7, +8,+8,+12,+i(12)(p10)x2[19],+15,+17,dic(18;19)(p11.3;q13) [6],-19,+20,+21,+21,+21,+21,+mar[cp19] (Fig. 1). FISH analysis confirmed the presence of 4 copies of chromosome 12 and 2 copies of i(12p), using M28 and YAC 958B8 (data not shown). DISCUSSION Cytogenetic analysis of a case of a malignant mixed OGCT revealed a highly abnormal karyotype. We found a hypertriploid/ hypotetraploid chromosome number (range 77–88) and several clonal structural abnormalities, including 2 copies of an i(12p) chromosome, the characteristic abnormality of TGCTs (van Echten et al., 1995). TGCTs are a well described cytogenetic entity. In a cytogenetic study of 95 primary TGCTs, we found them to have a characteristic chromosomal pattern, with chromosome numbers in the triploid range and characteristic chromosomal over-representation (7, 8, 12, 21 and X) and under-representation (11, 13 and 18). In 83% of the non-seminomatous TGCTs, we found an i(12p) chromosome (van Echten et al., 1995). The chromosomal pattern of the present case of a malignant OGCT shows strong similarities with that of TGCTs: a hypertriploid/ hypotetraploid chromosome number, presence of i(12p), and over-representation of chromosome 7, 8, 12 and 21. This finding suggests that GCTs of the ovary and the testis may have a similar origin and pathogenesis. Furthermore, chromosomal similarities between malignant OGCTs and TGCTs are clear from the literature. An i(12p) chromosome has been found in 5 cases: 2 dysgerminomas (Jenkyn and McCartney, 1987; Atkin and Baker, 1987), a yolk-sac tumor (Speleman et al., 1990), a mature teratoma (Speleman et al., 1992) and a malignant teratoma (Hoffner et al., 1992). Mascarello et al. (1993) described the presence of an i(12p) in a mixed OGCT, associated with a myelodysplasia, using FISH analysis. A yolk-sac *Correspondence to: Department of Medical Genetics, University of Groningen, Ant. Deusinglaan 4, 9713 AW Groningen, The Netherlands. Fax: (31) 50-363-2947. E-mail: J.van.Echten-Arends@Med.Rug.nl Received 24 November 1997; Revised 4 March 1998 Int. J. Cancer: 77, 217–218 (1998)  1998 Wiley-Liss, Inc. Publication of the International Union Against Cancer Publication de l’Union Internationale Contre le Cancer