ELSEVIER

Cytogenetic Findings in Uterine Epithelioid Leiomyomas

Christos Karaiskos, Nikos Pandis, Georgia Bardi, Kostas Sfikas, Aliki Tserkezoglou, Stelios Fotiou, and Sverre Heim

ABSTRACT: Epithelioid leiomyomas of the uterus, unlike ordinary leiomyomas, show substantial epi- thelial differentiation. No chromosome abnormalities have been reported in uterine epithelioid leiomyomas before. We analyzed short-term cultures from five such tumors and detected abnormal karyotypes in four. A del(7) (q21.2q31.2) was found in two tumors, in one as the only change and in the other as a secondary aberration acquired during clonal evolution. Rearrangement of chromosomal band 12q15, another of the cytogenetic hallmarks of ordinary uterine leiomyomas, was seen in the form of a t(10;12) in one tumor. Band 17q21 was involved in structural aberrations in two cases. The data we present indicate that epithelioid leiomyomas are fundamentally similar cytogenetically, and hence presumably also pathogenetically, to the much more common smooth muscle-differentiated uterine myomas. The only differences hinted at are that epithelioid tumors may be karyotypically more complex and more often have rearrangements of 17q21.

INTRODUCTION

Leiomyoma is the most common smooth muscle tumor. Al- though rare in other organs, it is f~equent in the uterus, where it is found in one-quarter of all women over 30 years of age [1]. Uterine ep i the l io id le iomyoma represents a rare variant wh ich consists p redominan t ly or exclusively of cells show- ing epi thel ia l differentiat ion [2]. Despite their benign histo- logic appearance, epi thel ioid leiomyoma8 are known to have a propensi ty to invade locally, to metastasize, and to recur [3].

Al though uter ine le iomyomas are some of the most ex- tensively cytogenet ical ly s tudied benign mesenchymal tumors in humans, no reports exist on the cytogenetics of ep i the l io id leiomyoma. We here descr ibed the karyotypic analysis of five such tumors, four of which were shown to have clonal chromosome abnormali t ies .

MATERIALS AND METHODS

Five myometr ial tumors from five hysterectomy specimens from premenopausa l women (Table 1) were cytogenetical ly and his tological ly examined. The tumors were in all cases shown to consist of smooth muscle t issue in which large and

From the Department of Cellular Physiology, "Papanikolaou Be- search Center" (C.K., N.P., G.B.), Department of Pathology (K.S.), and First Department of Gynecology (A.T., S.F.), Saint Savas Hos- pital, Athens, Greece; Department of Medical Genetics (N.P., G.B., S.H.), Odense University, Denmark; and Department of Clinical Genetics (N.P, G.B., S.H.), University Hospital, Lund, Sweden.

Address reprint requests to: Dr. Nikos Pandis, Department of Clin- ical Genetics, Lund University Hospital, S-221 85 Lund, Sweden.

Received June 20, 1994; accepted August 8, 1994.

Cancer Genet Cytogenet 80:103-106 (1995) © Elsevier Science Inc., 1995 655 Avenue of the Americas, New York, NY 10010

numerous foci of epi the l ia l differentiation, judged to make up from 40% to 70% of the total t issue mass, were seen (Fig. 1). The cells in these foci were round to polygonal , wi th a granular eos inophi l ic cytoplasm. Most nucle i were eccen- t r ical ly located. The diagnosis was ep i the l io id leiomyoma.

Samples for cytogenetic analysis were taken from tumor areas that on neighboring sections were histologically shown to contain epi thel io id leiomyoma differentiation. The tissue was minced wi th scissors and subjected to enzymat ic dis- aggregation in 210-240 U/mL collagenase for 20-24 hours. The resulting cell suspensions were washed, plated out, and

Table 1 Cl in icopathologic and karyotypic f indings in five epi the l io id le iomyomas

Case Age no. (yrs) (cm) Karyotype

1 37 7.5

2 33 6

3 43 6 4 50 3.6 5 53 10

46,XX,t(10;12)(q22;q15)[41]/46,idem, del(7)(q21.2q31.2)[281]/46,idem,del(7) (q21.2q31.2),dup(17)(q21q25)[6]/46, idem,del(7)(q21.2q31.2),dic(17;21) dup(17)(q21q25)t(17;21)(q25;p11-13) [80]/45,idem,del(7)(q21.2q31.2), der(13;21)(q10;q10)[39]/45,idem, del(7)(q21.2q31.2),der(21;21) (q10;q10)[13]/46,XX[12]

45,XX,ins(2;8)(q31;q13q22),der(8) t(8;17)(q11;q21), - 17187]/46,idem, + r[1207]/46,XX[23]

46,XX,del(7)(q21.2q31.2)[75]/46,XX[40] 46,XX,inv(3) (p2 lq27)[ 7]/46,XX[9] 46,XX[180]

0165-4608/95/$9.50 SSDI 0165-4608(94)00167-A

104 C. Karaiskos et al.

cultured in RPMI 1640 medium that had been supplemented with 17% fetal calf serum, glutamine (0.23 mg/mL), estradiol (10- 7 M), progesterone (10- 7 M), and antibiotics. Cases 32 and 58 were grown in flasks, cases 43, 46, and 53 on in situ slides in flaskettes. After 6-17 days, the cultures were har- vested as described by Pandis et al. (1990) [4] for flask cul- tures and Pandis et al. {1991) [5] for flaskette cultures. The preparations were G-banded using Wright's stain. The sub- sequent cytogenetic analysis followed the recommendations of the ISCN (1991) [6].

F i g u r e I Histologic section illustrating the epithelioid differen- tiation in case 2. H-E, x 400.

E

10

l 12

13 21 21 7 17

), I

]1

17

41

2 8 17 r 7 3

F i g u r e 2 Partial karyotypes illustrating the clonal chromosomal abnormalities in cases 1 (upper two rows; the ar- rows point at changes acquired during clonal evolution), 2 (lower row left), 3 (lower row middle-right, deletion of chromosome 7), and 4 (lower row extreme right, inversion of chromosome 3). Arrowheads indicate breakpoints.

Uterine Epi the l io id Leiomyomas 105

RESULTS

A normal chromosome complement was found in case 5, but the other four tumors had clonal chromosome abnormali- t ies (Table 1, Fig. 2). Clonal evolution was seen in cases 1 and 2, which contained both complex aberrations and cytoge- net ical ly related clones. A del(7) (q21.2q31.2) was the only recurrent change, found in cases 1 and 3.

DISCUSSION

Although it is now well known that uterine leiomyomas carry tumor-specif ic chromosome aberrations, no less than 50- 80% of myomas have only normal karyotypes [7]. The data we present here are much too l imi ted to al low any quantita- tive conclusions, but we believe it could be a reflection of inherent tumor biology that as many as 80% of this small series of ep i the l io id uter ine myomas tu rned out to be karyo- typ ica l ly abnormal . Epi the l io id le iomyomas (leiomyoblas- tomas) are more aggressive than ordinary leiomyomas; Lavin et al. (1972) [8] conc luded that they "ought to be cons idered potent ia l ly mal ignan t" and Kyriazis and Kyriazis (1992) [3] concurred that these tumors "should be viewed as neoplasms of low-grade mal ignancy of a dis t inct c l in icopathologic en- tity" We have previously shown that a histologic-cytogenetic para l le l i sm exists for uterine myomas, wi th more complex karyotypes being found in those that have the highest cel- lularity, mitot ic activity, and other signs of tumor progres- s ion [9, 10]. The relat ively extensive chromosomal aberra- t ions in the ep i the l io id le iomyomas descr ibed here (subclones were present in two of the four karyotypical ly ab- normal tumors, cases I and 2) are consistent wi th the exis- tence of such a correlat ion also for myometr ial neoplasms wi th epi the l ia l differentiation.

The most common cytogenetic abnormal i t ies in uterine myomas are intersti t ial delet ions of the long arm of chromo- some 7, as the sole change or occurring secondarily, and rear- rangements of 12q13-15, in par t icular t(12;14) [7]. In two of our cases, the leiomyoma-specif ic del(7) (q21.2q31.2) was de- tected, as the only anomaly in case 3 and as a secondary change in case 1 (Table 1, Fig. 2).

The t(10;12) (q22;q15) of our case I (Fig. 2) is not just an- other example of a structural rearrangement of 12q13-15 in myomas, it is exactly the same t ranslocat ion that has been descr ibed previously in a uterine le iomyoma by Stern et al. (1992) [11]. Ozis ik et al. (1993) [12] repor ted two more cases of t(10;12) in which the breakpoin t in chromosome 10 was the same, but where the one in chromosome 12 had been mapped to band 12q13 in one tumor and to 12q14 in the other. Al though we now are of the op in ion that most, if not all, 12q13-15 rearrangements in le iomyoma actual ly have the breakpoin t in 12q15 [13], it is clear that h igh-resolut ion cytogenetic mapp ing of breaks in this region is extremely difficult; hence, we th ink it is l ikely that all four 10;12 trans- locat ions referred to above may have been identical . This means that t(10;12) (q22 ;q13-15) characterizes a new cytoge- netic subgroup in uterine leiomyomas, albeit one that is much less common than the main subset def ined by the presence of t(12;14) (q14-15;q23-24). The gene loci of impor tance for myoma development in 10q22, 12q15, and 14q24 are un- known.

The cytogenetic f indings therefore indicate a fundamen- tal s imilar i ty between epi the l io id and other uterine leiomyo- mas, arguing for the hypothesis that the pathogenetic mech- anism is basical ly the same in all these tumors. One caveat should be kept in mind when drawing this conclusion, how- ever. The examined tumors contained a mixture of cells with smooth muscle and epi thel ia l differentiation, both in vivo and, judging from the cultural morphology, in vitro. There are no posit ive indicat ions to this effect, but we cannot be absolutely certain that there was not a significant over- representat ion of cells showing smooth muscle differentia- t ion among those we karyotyped.

That basic cytogenetic s imilar i t ies exist between epithe- l ioid and other uterine leiomyomas should not be interpreted to mean that genetic differences play no role in bringing about the phenotyp ic variability. The fact that ep i the l io id tumors might be karyotypical ly more complex has a l ready been re- ferred to. In addi t ion, two of the four abnormal tumors had secondary structural rearrangements of chromosomal band 17q21. Because this is so infrequent in other l e i o m y o m a s - only three cases have been reported [4,14,15] - t h e s e changes could be more int imately l inked to epi the l io id differentia- t ion than to le iomyoma tumorigenesis as such.

This study was supported by grants from the Hellenic Anticancer Society. The technical assistance of Marina Margaroni is gratefully acknowledged.

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