GENES, CHROMOSOMES & CANCER 5:178-180 (1992)

Chromosome Changes in a Case of Hibernoma Paola Dal Cin, Boudewijn Van Damme, Michel Hoogmartens, and Herman Van Den Berghe

Center for Human Genetics (P D C H V D 6 ) and Department of Pathology (B V D), University Hospital Gasthuisberg, and Department of Orthopedic Surgery, University Hospital Pellenberg (M H ) , University of Leuven. Belgium

Cytogenetic analysis of a rare adipose tissue tumor, hibernoma, a benign proliferation of the brown fat, is presented for the first time. A complex translocation involving bands I p36, 2q33, 5q22, and I I q I 3 was found as the sole chromosome abnorm- ality. Genes Chrom Cancer 5:178-180 ( I 992).

Hibernomas are rare tumors with a characteristic histological appearance causing no differential diag nostic problems. The main feature of the tumor is its similarity to normal brown fat, found in the neck and lumbar region of fetuses and children. Tumors with this appearance occur most frequently in the neck, scapular, and interscapular region, but are not re-

A 42-year-old bar keeper was seen in August 1991 because of a painless mass in the left buttock that had existed for approximately 4 years. The lump had a diameter of about 10 cm, it was soft and mobile, and there was no regional lymphadenopathy. Clinical in- vestigation otherwise was unremarkable. CT scan

stricted to these areas and can occur everywhere. The tumor is, surpi-kingly, rare in children (Enzinger and Received 1)ecembcr 27, 1991, acccptcd Januanr 27. 1991

Addrcsa repnnt requests to 11 V m Den Ucrghc, Centcr for Weiss, 1988). I Iuman Genetics. 1lerestra:ct 4'). 3000 Leu\ en, Belgium.

A Overview of the tumor. showing evenly distributed vacuolated cells. arranged in lobules, separated by a thin septum (H&E x 65). B: Detail of the variation in size of the lipid vacuoles in the tumor cells (H&E x 260).

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I80 DAL CIN ET A L

showed a 7.8 cm large tumor in the left gluteus max- imus muscle with well-defined borders. Magnetic res- onance imaging showed loss of fat tissue delineation between the tumor and the quadratus femoris muscle as well as the sciatic nerve. The whole left gluteus maximus muscle was removed. No invasion of sur- rounding tissues was found.

The tumor consisted of large, mostly vacuolated cells with a somewhat eosinophilic cytoplasm. They were arranged in lobules, similar to normal fat, sepa- rated by mostly thin fibrous septa (Fig. 1A). In some areas the septa were wide and contained prominent blood vessels. The vacuoles were empty, after routine tissue dehydration, and varied in size from very small up to the size of normal fat cells (Fig. IB). This histo- logical picture was considered to be characteristic of a hibernoma.

Chromosome analysis was performed on 30 G-banded metaphase cells from a 5-day-old culture, according to the procedures previously described (Peakman et al., 1977; Limon et al., 1986). Eighteen cells had a complex four-way translocation: the llq13+llqter segment was translocated to 5q22, 5q22h5qter to 2q33, and 2q3342qter to lp36 (Fig. 2). The karyotype could thus be described as 46,XY,t(l;ll;5;2)(p36;q13;q22;q33). Two metaphase cells exhibited a t(810)(q24;q22) in addition to the four-way translocation. The remaining cells had a normal male karyotype.

Cytogenetic examinations of lipomas have identi- fied subtypes characterized by recurrent and specific aberrations involving 12q13-14, 13q12-22, and 6 ~ 2 1 - 23 (for review see Sreekantaiah et al., 1991) and the presence of an extra ring (Mandahl et al., 1988). Three benign adipose tissue tumors other than ordinary lipomas and atypical lipomas have been cytogeneti-

cally investigated: de1(4), de1(6), and inv( 13) were pre- sent in a fibrolipoma, t(7;8) in a lipoblastoma (Sand- berg et al., 1986), and an extra chromosome 7 in an angiolipoma (de Jong et al., 1988). Since the present report is the first cytogenetic characterization of this very rare benign tumor of the brown fat, no conclu- sions or correlations can be drawn, except that bands lp36 and llq13 have been described before in nonran- dom rearrangements in lipomas (Sreekantaiah el. al., 1991).

ACKNOWLEDGMENTS

This work was supported by the Inter-University Network for Fundamental Research sponsored by the Belgian Government (1991-1995). The authors wish to thank Lutgarde Meekers and Magda Dehaen for their expert technical assistance and Rita Logist for clerical assistance.

REFERENCES

de Jong €3, Castedo SMMJ, Oosterhuis JW, Dam A (1988) Letter to the editor. Trisomy 7 in a case of angiomyolipoma. Cancer Genet Cyto- genet 3421SL222.

Enzinger FM, Weiss SW (1988) Soft Tissue Tumors, Ed. 2. St. Louis, M O C.V. Mosby Co.

Limon J, Dal Cin P, Sandberg A A (1Y86) Application of long-term col- lagenase disaggregation for the cytogenetic analysis of human solid tumors. Cancer Genet Cytogcnet 23:305-313.

Mandahl N, Heim S, Arheden K, Rydholm A, Willen H, Mitelnian F (1988) Three major cytogenetic subgroups can be identified among chromosomally abnormal solitary lipomas. Hum Genet 79 20S208.

Peakman Dc, Moreton MF, Robinson A (1977) Prenatal diagnosis: Tech- niques used to help in ruling out maternal contamination. J Med Genet 14:37 39.

Sandberg AA, Gibas Z, Saren E, Li FP, Limon J, Tebbi CK (1986) Chromosome abnormalities in two benign adipose tumors. Cancer Genet Cytogenet 22:5M1.

Sreekantaiah C, Leong SPL, Karakousis CP, McGee DL, Rappaport WD, Villar HV, Neal D, Fleming S, Wankel A, Herrington PN, Carmona R, Sandberg AA (1991) Cytogenetic profile of 109 lipomas. Cancer Res 51:422 433.