Clonal chromosome abnormalities in two liposarcomas

Clonal Chromosome Abnormalities in Two Liposarcomas Fredrik Mertens, Bertil Johansson, Nils Mandahl, Sverre Heim, Kristina Bennet, Anders Rydholm, Helena Will6n, and Felix Mitelman

ABSTRACT: Two liposarcomas were analyzed with chromosome banding technique. The sole chromosomal abnormality in one of the tumors, a mixed type (myxaid and round cell) liposarcoma, was t(12;16)(q13;p11), a rearrangement previously reported to be associated with myxoid liposarcoma. The other tumor, a pleomorphic liposarcoma, displayed massive numerical rearrangements (modal chromosome number 94-112), and numerous, mostly unidentifiable, marker chromosomes. The following clonal structural aberrations were recognized: del(1)(p22), del(1)(q23), t(7;?)(p22;?), i(17q), and t(19;?)(q13;?). INTRODUCTION In the past few years the k n o w l e d g e concerning c h r o m o s o m a l aberrations in mese n c h y m a l tumors has increased. A l t h o u g h the n u m b e r of cases analyzed is still very low, specific translocations have been found in several t u m o r types, i.e., t(11;22)(q23-q24;q12) in Ewing's sarcoma [1, 2], t(12;16)(q13;p11) in m y x o i d liposarcoma (MLS) [3], and t(X;18)(p11;q11) in synovial sarcoma [4]. Quite recently, lipomas have been s h o w n to have n o n r a n d o m structural rearrangements of 12q13q14 [5-7]. We present herein further evidence for the association between t(12;16)(q13;p11) and MLS, and describe a p l e o m o r p h i c liposarcoma with a highly c o m p l e x karyotype. CLINICAL DATA Case 1

A p r e v i o u s l y h e a l t h y 43-year-old m a n had noticed, over a period of 6 months, a slowly growing painless mass in his right leg. A n g i o g r a p h y and c o m p u t e d tomogr a p h y s h o w e d a t u m o r in the soleus muscle. There were no signs of metastases. A s p i r a t i o n cytology suggested a m y x o i d liposarcoma. The muscle including the 14

From the Departments of Clinical Genetics (F. M., B. J., N. M., S. H., K. B., F. M.), Orthopaedic Surgery (A. R.), and Clinical Pathology (H. W.), University Hospital, Lund, Sweden. Address requests for reprints to Fredrik Mertens, Department of Clinical Genetics, University Hospital, S-221 85 Lurid, Sweden. Received November 10, 1986; accepted January 20, 1987.

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Case 2

A previously healthy 57-year-old man was referred because of a tumor, noticed for 4 months, in the right buttock. Computed tomography showed a tumor in the gluteus maximus muscle. There were no signs of metastases, Aspiration cytology suggested a highly malignant liposarcoma. The muscle including the 9 x 7 x 7 cm large, well circumscribed tumor was extirpated. The histopathologic examination revealed a myxoid tissue mixed with highly cellular areas with numerous undifferentiated or anaplastic lipoblasts (Fig. 2a). Fat cells with a large number of fat droplets in the cytoplasm were observed under electron microscopy (Fig. 2b). The tumor was classified as a pleomorphic liposarcoma, grade IV [8]. Eighteen months after the operation the patient remains without signs of local recurrence or metastases. CYTOGENETIC INVESTIGATION Tumor specimens were mechanically disaggregated and treated with 0.8% collagenase [9]. Short-term cultures were initiated in flasks (Nunc) and Flaskettes (Lux) [10] using RPMI 1640 m e d i u m with Hepes buffer, supplemented with 17% fetal calf serum, glutamine, and antibiotics. The cultures were harvested after 5 days and the slides were stained with a standard trypsin-Giemsa banding technique. RESULTS Case 1

The only clonal abnormality was a reciprocal translocation between chromosomes #12 and #16, t(12;16)(q13;p11), which was found in 13 of 14 mitoses analyzed (Fig. 3). This rearrangement was found in two samples taken from different locations of the tumor. Case 2

Of 42 mitoses analyzed the majority had hypertetraploid chromosome numbers ranging from 94 to 112 (Fig. 4a). At least 35 marker chromosomes were present, including ring chromosomes in two mitoses. The only clonal structural aberrations that could be identified were: del(1)(p22), del(1)(q23), t(7;?)(p22;?), i(17q), and t(19;?)(q13;?) (Fig. 4b). Double minutes were seen in three mitoses. DISCUSSION

Despite the low number of liposarcomas investigated so far with cytogenetic techniques, some interesting features have already emerged. The best studied histopathologic subtype is MLS. Six cases, including case 1 of the present report, have been successfully analyzed, and all had similar chromosome abnormalities. Of the four

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F i g u r e 4 (A) Metaphase plate from case 2; (B) Identifiable clonal chromosome markers from one metaphase of case 2 showing, from left to right: del(1)(p22)', del(1)(q23), t(7;?)(p22;?), i(17q), and t(19;?)(q13;?). Arrows indicate breakpoints.

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cases reported by Turc-Carel et al. [3], three had t(12;16)(q13;p11) and the fourth a more complex, three-way translocation, t(1;12;16)(p11;q13;p11). In the case reported by Becher et al. [11], a der(12) was found as one of several abnormalities. These findings, not least the fact that t(12;16)(q13;p11) has been the sole aberration in two of the six cases, strongly suggest that this rearrangement is of prime importance in the pathogenesis of MLS. A similar t(12;16) has not been described in any other neoplasm [12]. Bands 12q13-q14 are also n o n r a n d o m l y involved in lipoma, the benign counterpart of liposarcoma [5-7]. The possible role of the oncogene c-int-1, mapped to 12pter-q14 [13], has been discussed w h e n trying to explain the significance of chromosome #12 rearrangements in lipomas and liposarcomas. However, no positive evidence of c-int-1 rearrangements has been reported so far in lipogenic tumors, and the molecular pathology of both the 12q breakpoint and the breakpoint in 1 6 p l l remains u n k n o w n . The second case was a highly malignant pleomorphic liposarcoma, a subtype that, to our knowledge, has not been cytogenetically analyzed before. Hypertetraploid cells with multiple structural anomalies dominated. None of the markers present showed any resemblance to a der(12) or a der(16) resulting from a t(12;16)(q13;p11). Multiple chromosomal abnormalities were also seen in the well differentiated liposarcoma described by Becher et al. [11], and in the unspecified liposarcoma described by Sonta et al. [14]. No consistent associations between these liposarcoma subtypes and cytogenetic markers can be recognized at present. Supported by grants from the Swedish Cancer Society and the J A P Foundation for Medical Research.

REFERENCES 1. Aurias A, Rimbaut C, Buffe D, Duboussett J, Mazabraud A (1983): Chromosomal translocations in Ewing's sarcoma. N Engl J Med 309:496-497. 2. Turc-Carel C, Philip I, Berger M-P, Philip T, Lenoir GM (1983): Chromosomal translocations in Ewing's sarcoma. N Engl J Med 309:497-498. 3. Turc-Carel C, Limon J, Dal Cin P, Rao U, Karakousis C, Sandberg AA (1986): Cytogenetic studies of adipose tissue tumors. II. Recurrent reciprocal translocation t(12;16) (q13;p11) in myxoid liposarcomas. Cancer Genet Cytogenet 23:291-299 4. Turc-Carel C, Dal Cin P, Limon J, Li F, Sandberg AA (1986): Translocation X;18 in synovial sarcoma. Cancer Genet Cytogenet 23:93. 5. Mandahl N, Heim S, Johansson B, Bennet K, Mertens F, Olsson G, R66ser B, Rydholm A, Will6n H, Mitelman F (1986): Lipomas have characteristic structural chromosomal rearrangements of 12q13-q14. J Int Canc (in press) 6. Heim S, Mandahl N, Kristoffersson U, Mitelman F, R66ser B, Rydholm A, Will6n H (1986): Reciprocal translocation t(3;12)(q27;q13) in lipoma. Cancer Genet Cytogenet 23:301-304. 7. Turc-Carel C, Dal Cin P, Rao U, Karakousis C, Sandberg AA (1986): Cytogenetic studies of adipose tissue tumors. I. A benign lipoma with reciprocal translocation t(3;12)(q28;q14). Cancer Genet Cytogenet 23:283-289. 8. Enzinger FM, Weiss SW (1983): Soft Tissue Tumors. C.V. Mosby, St. Louis. 9. Gibas LM, Gibas Z, Sandberg AA (1984): Technical aspects of cytogenetic analysis of human solid tumors. Karyogram 10:25-27. 10. Mandahl N, Gustavii B, Heim S, Kristoffersson U, Mineur A, Mitelman F (1985): Technical aspects of long-term culture and cytogenetic analysis of first trimester chorionic villi. Karyogram 11:10-13. 11. Becher R, Wake N, Gibas Z, Ochi H, Sandberg AA (1984): Chromosome changes in soft tissue sarcomas. J Natl Cancer Inst 72:823-831.

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12. Mitelman F (1985): Catalog of Chromosome Aberrations in Cancer, 2nd ed. Alan R. Liss, NY. 13. Nusse R, Veer LV, Geurts van Kessel A, van Agthoven A, Bootsma D, Varmus H (1984): Chromosomal localization of a human homologue of a putative mammary tumor oncogene. Cytogenet Cell Genet 37:556-557. 14. Sonta S, Oshimura M, Evans JT, Sandberg AA (1977): Chromosomes and causation of human cancer and leukemia. XX. Banding patterns of primary tumors. J Natl Cancer Inst 58:49-59.