Distinction between lipoma and liposarcoma by MDM2 alterations: a case report of simultaneously occurring tumors and review of the literature

We investigated a lipoma and a well-differentiated/dedifferentiated liposarcoma (WD/DDL), occurring simultaneously in one patient for the possible role of p53 and mdm2 in the molecular oncogenesis of liposarcoma and tumor progression. The hypothesis tested was if there is a continuum in the development from lipoma to liposarcoma. Lipoma was characterized by a lack of p53 mutation, p53 LOH and p53 protein expression, as well as by mdm2 amplification and mdm2 protein expression. p53 mutation and p53 LOH were found neither in the well-differentiated nor in the dedifferentiated parts of the liposarcoma. In contrast, mdm2 amplification and an increase in mdm2 protein expression were found to be associated with malignancy and dedifferentiation, whereas p53 protein expression was only slightly increased. These findings indicate that mdm2 constitutes one of the most common targets for molecular aberration in WD/DDL. We suggest that mdm2 is a marker distinguishing between ordinary lipoma and well-differentiated liposarcoma, and that the genesis of these tumors is different.

Investigating evolutionary lines of least resistance using the inverse protein-folding problem

We present a polynomial time algorithm for estimating optimal HP sequences that fold to a specified target protein conformation based on Sun et al's Grand Canonical (GC) model. Application of the algorithm to related proteins taken from the PDB allows us to explore the nature of the protein genotype:phenotype map. Results suggest: (1) that the GC model captures important biological aspects of the mapping between protein sequences and their corresponding structures, and (2) the set of sequences that map to a target structure with optimal energy is affected by minor differences in structure.

Distinct cytologic features of spindle cell lipoma. A cytologic-histologic study with clinical, radiologic, electron microscopic, and cytogenetic correlations

BACKGROUND

Spindle cell lipoma (SCL) is a relatively uncommon, benign tumor that usually presents in the subcutaneous fat of adult men. Although some studies have addressed the histologic findings of SCL, only a few descriptions of aspiration cytology findings have been published. The cytologic features are poorly defined, and aspirates from SCL may cause diagnostic problems, because SCL shares some features with other fatty/spindle cell or myxoid lesions, benign as well as malignant.

METHODS

Twelve patients underwent fine-needle aspiration (FNA) cytology as the primary diagnostic modality before surgery. FNA findings were evaluated and correlated with histologic features. In addition, radiologic, electron microscopic, and cytogenetic findings were analyzed. The objective of this study was to determine cytologic criteria of SCL by reviewing cytologic specimens in 12 patients with SCL who underwent FNA cytology.

RESULTS

All of the tumors arose in adults, and 10 tumors developed in the subcutaneous tissue of the neck, back, or shoulder girdle. Two patients presented with tumors in atypical locations; one in the tongue and one in the cheek. Cytologically, all 12 tumors were characterized by a mixture of mature adipocytes, uniform spindle cells, and collagen bundles and/or fibers in varying proportions. The presence of a myxoid matrix and of mast cells was less specific and occurred in six aspirates.

CONCLUSIONS

SCL has a characteristic cytologic appearance that, together with clinical data, helps to exclude low-grade liposarcoma as well as other spindle cell and myxoid lesions.

The genetics of lipomatous tumors

The current classification of lipomatous neoplasms has been validated by the identification of characteristic cytogenetic and molecular genetic profiles associated with various neoplasms within the family of lipomatous tumors. The review describes characteristic cytogenetic and molecular genetic profiles and discusses their significance. The clinicopathologic features of these tumors, which are described elsewhere, will not be included in this review.

Large deletion of part of the HMGIC locus accompanying a t(3;12)(q27 approximately q28;q14 approximately q15) in a lipoma

The high mobility group protein gene HMGIC has been found to be rearranged in a variety of human benign solid tumors. Often, these rearrangements lead to fusion genes of which that between HMGIC and LPP underlying t(3;12)(q27 approximately q28;q14 approximately q15) is by far the most common. Herein, we analysed a lipoma with a t(3;12)(q27 approximately q28;q14 approximately q15). RT-PCR revealed the presence of a HMGIC-LPP fusion transcript composed of exons 1-3 of HMGIC and exons 9-11 of LPP, but the absence of the reverse LPP-HMGIC fusion transcript. Fluorescence in situ hybridization experiments using different probes derived from the HMGIC gene and its 3' vicinity showed the absence of FISH signals on the derivative chromosome 3. Thus, in the present tumor the t(3;12)(q27 approximately q28;q14 approximately q15) was accompanied by a large genomic deletion. Roughly, it can be estimated that at least 170 kb of chromosome 12 material were deleted. To the best of our knowledge, this is the first report showing that the "simple" t(3;12)(q27 approximately q28;q14 approximately q15) results in a large deletion of DNA.

[Spindle cell lipoma and 13q deletion: diagnostic utility of cytogenetic analysis]

AIM

Spindle cell lipomas are rare adipose tissues tumors. Histologically, these lesions are composed of mature adipocytes and spindle cells associated with collagen bundles. Spindle cell lipomas are benign tumors that can be difficult to distinguish from malignant tumors such as spindle cell liposarcomas, myxoid liposarcomas or well-differentiated liposarcomas.

RESULTS

We report herein the description of two new cases. The first case was a deeply situated and infiltrating tumor located in the retromastoidian area. The karyotype showed the presence of two chromosomal abnormalities, a partial deletion of the long arm of chromosome 13, del(13)(q12) and a balanced reciprocal translocation t(2;6)(p16~21;p21). The second case was a subcutaneous tumor of posterior cervical localization. The karyotype showed a 13q deletion associated with a complex rearrangement of chromosomes 5, 6 and 10. The presence of the 13q deletion allowed us to confirm the diagnosis of spindle cell lipoma in both cases. This deletion has been previously described in six out the eleven published karyotype reports. The 13q deletion is usually associated with partial monosomy 16. The present case confirms that it can occur independently. The 6p21 rearrangement may also play a role in the pathobiology of this tumor, as suggested by the positive HMGIY expression detected by immunohistochemistry.

CONCLUSION

Our study further illustrates that spindle cell lipomas can infiltrate the surrounding muscle and emphasizes the usefulness of cytogenetic analysis in the differential diagnosis of soft tissue tumors.

Cytogenetic and molecular genetic analyses of liposarcoma and its soft tissue simulators: recognition of new variants and differential diagnosis

Liposarcoma is one of the most common sarcomas of adults. Its differential diagnosis and accurate subclassification are often problematic; the latter is also important with regard to appropriate treatment and prognosis. We studied a series of 23 liposarcomas that had unusual or previously undescribed features and 10 liposarcoma simulators and correlated the morphologic, cytogenetic, and molecular genetic findings. We found that use of cytogenetic-molecular genetic techniques aids in the distinction between myxoid-round cell liposarcoma and their simulators, chondroid lipoma, myxoid spindle cell-pleomorphic lipoma, cellular intramuscular myxoma, and myxofibrosarcoma. Poorly differentiated forms of round cell liposarcoma lacking morphologic evidence of lipogenesis can also be diagnosed using these techniques; however, the techniques do not aid in distinguishing low-grade myxoid from high-grade round cell liposarcomas. This study also shows that retroperitoneal liposarcomas with myxoid liposarcoma-like zones are part of the morphologic spectrum of well-differentiated-dedifferentiated liposarcoma rather than true myxoid liposarcomas. Perhaps most importantly, our results provide the first molecular genetic evidence that true mixed liposarcomas (mixed well-differentiated and myxoid liposarcoma) do indeed exist. They also unequivocally demonstrate the existence of small, round cell variants of pleomorphic liposarcoma that closely simulate myxoid-round cell liposarcoma.

The contribution of image cytometry to the characterization of clinical subgroups of lipomas

The aim of the present study was to investigate whether biological features determined through image cytometry are able to characterize clinical subpopulations of lipomas. Forty lipomas excised from 36 patients were studied. On the one hand, the tumors were clinically characterized by means of patient-related and pre- and post-operative features. On the other, the tumors were analyzed by means of the computer-assisted microscopy analysis of Feulgen-stained nuclei. This analysis generated 3 groups of biological quantitative variables describing morphonuclear aspects (i.e. the chromatin pattern of the cell nuclei), the nuclear DNA content (DNA ploidy level), and architectural features (such as the cell density and the topographical cell nuclei organization). Possible relations between the clinical and the biological features of the lipomas were investigated by means of univariate and multivariate statistical analyses. The results show the existence of such relations, in particular between the morphonuclear and architectural features of lipomas, on the one hand, and their consistency, volume and weight, on the other. Furthermore, multivariate analysis made it possible to distinguish two subpopulations of lipomas exhibiting different biological characteristics in terms of morphonuclear patterns.

Leptin and leptin receptor mRNA are widely expressed in tumors of adipocytic differentiation

Adipose tissue is the principal source of leptin, a cytokine-like peptide with many biologic functions. Leptin binds to the leptin receptor, present in the hypothalamus and in many other tissues, and modulates energy balance and maintenance of body weight. The expression of leptin and leptin receptor in tumors of adipocytic differentiation has not been previously examined. Because normal adipose tissue is the principal source of leptin and expresses leptin receptor, we hypothesized that tumors of adipose tissue differentiation may also express leptin and/or the long functional form of the leptin receptor (OB-Rb). Leptin and OB-Rb were analyzed by immunohistochemistry, in situ hybridization, RT-PCR, and western blotting in 21 lipomas, 2 hibernomas, and 16 liposarcomas. Immunostaining and in situ hybridization showed leptin and OB-Rb mRNA expression in all cases of lipomas, hibernomas, and liposarcomas, including dedifferentiated and pleomorphic liposarcomas. RT-PCR analysis showed leptin and OB-Rb mRNA in both lipomas (n = 5) and liposarcomas (n = 5). Western blotting identified the 16 kDa leptin protein in a lipoma and a liposarcoma. No important difference in the expression of leptin and OB-Rb mRNA was found between lipomas and liposarcomas, although the level of leptin protein was higher in a lipoma than a liposarcoma by western blotting. These results show for the first time that leptin and OB-Rb mRNA are expressed in lipomas, hibernomas, and liposarcomas. The presence of leptin and its receptor may provide new insights into the pathobiology of these tumors.

Tumors and the heart: molecular genetic advances

Recent molecular genetic investigations of primary cardiac tumors (myxomas, lipomas, rhabdomyomas, and fibromas) have provided insight into fundamental mechanisms of cardiac cell growth. Myxomas are the most common adult cardiac tumor, and familial cardiac myxomas are now appreciated to be caused by mutations in the PRKAR1alpha gene that encodes a regulatory subunit of protein kinase A. Cytogenetic studies have targeted candidate chromosomal loci that may be perturbed during cardiac lipoma pathogenesis. Rhabdomyomas, the most common pediatric cardiac neoplasm, are frequently associated with tuberous sclerosis, caused by mutations in the TSC-1 and TSC-2 genes. The study of Gorlin syndrome has shed light on the etiology of cardiac fibromas. This disorder is caused by mutation of the PTC gene, which regulates cell growth, commitment and differentiation. In the future, manipulation of PRKAR1alpha-, TSC-, and PTC-dependent pathways may foster new strategies to regenerate myocardium in the ischemic or myopathic heart.

Evidence by spectral karyotyping that 8q11.2 is nonrandomly involved in lipoblastoma

We report two cases of lipoblastoma with chromosome 8-related aberrations, ie, a 92,XXYY,t(7;8Xp22;q11.2)x2 [8]/46,XY[16] in Case 1 and a 46,XY,-8,-13,add(16) (q22),+mar, +r [cp13]/46,XY[7] in Case 2. Using spectral karyotyping and fluorescence in situ hybridization techniques, the karyotype of Case 2 was redesignated as 46,XY, r(8), del(13)(q12), der(16)ins(16;8)(q22; q24q11.2)[cp13]/46,XY[7]. This report delineates a new chromosome rearrangement, ie, der(16)ins(16;8)(q22; q24q11.2) in lipoblastoma, and also confirms the t(7; 8)(p22;q11.2), reported only once previously, as a recurrent translocation involved in such a tumor. These findings provide valuable information for clinical molecular cytogenetic diagnosis of lipoblastoma. Furthermore, this report highlights the value of cytogenetic and molecular cytogenetic analysis in differential diagnosis of childhood adipose tissue tumors and adds to the number of lipoblastomas reported with chromosomal abnormalities at 8q11.2.

Lipoblastoma with aberration in the long arm of chromosome 8

We report a case of lipoblastoma in a 6-month-old girl with a new chromosomal aberration, 46, XX, der (2) add (2) (p23) del (2) (q33), add (8) (q1?). In addition to the patient's age and pathological features, aberration of long arm of chromosome 8 in lipoblastoma can assist the differential diagnosis from myxoid or well differentiated liposarcoma.

Case of lipoblastoma with two derivative chromosomes 8 containing homogeneously staining-like regions and a review of the literature: lipoblastoma and chromosome 8

We report a case of a lipoblastoma in a 10-month-old girl in which the cytogenetic aberration showed a homogeneously staining-like region (hsr) within two derivative chromosomes 8. There was a loss of one normal copy of chromosome 8 and gain of two identical derivative chromosomes 8 with the karyotype designation 47,XX,psu idic(8)(pter-->q12 approximately 13::hsr::q12 approximately 13-->pter),+psu idic (8)(pter-->q12 approximately 13::hsr::q12 approximately 13-->pter). This is the first report of a chromosomal aberration of this type seen in lipoblastoma.

Angiomyxolipoma shares cytogenetic changes with lipoma, spindle cell/pleomorphic lipoma and myxoma

Angiomyxolipoma is a rare variant of lipoma, two cases of which have recently been described. We report on the hitherto unreported clonal chromosomal changes of a third case of angiomyxolipoma. The karyotype showed a 46,XX,t(7;13)(p15;q14),t(8;12)(q13;p13)[17]/46,XX[3]. The involvement of 13q14, 12p13, and 8q13 supports a relationship with other types of benign lipomatous and myxoid tumors.

Spindle cell lipoma of the foot and the application of CD34 immunohistochemistry to atypical lipomatous tumors in unusual locations

Spindle cell lipoma demonstrates a distinctive histologic appearance and characteristic clinical presentation. We recently observed two cases of solitary subcutaneous neoplasm of the foot with histologic features of spindle cell lipoma that in one case includes a minor component of the overlapping tumor, pleomorphic lipoma. Because the foot is an unusual location for these neoplasms, immunoperoxidase and cytogenetic studies were performed. In both cases, staining was strongly positive for CD34 and negative for smooth muscle actin. Cytogenetic studies from the tumor with a pleomorphic component revealed features consistent with a lipomatous neoplasm, but are otherwise diagnostically nonspecific. An analysis of the literature reveals that although CD34 immunoreactivity is characteristic of spindle cell lipoma and helps exclude nonlipomatous neoplasms, it does not clearly eliminate other well-differentiated lipomatous tumors. Accordingly, without the aid of classic tumor location, the diagnosis of the spindle cell/pleomorphic lipoma group relies primarily on histologic features, with supportive but not definitive information provided by immunoperoxidase and cytogenetic studies. Obscuring this issue, however, are the imprecise histologic distinction between these tumors and those of the atypical lipoma/atypical lipomatous tumor/ well-differentiated liposarcoma group and the nomenclature controversy that surrounds the latter group of neoplasms. Despite these obstacles, both groups of well-differentiated lipomatous tumors are clinically benign when subcutaneously located.

PLAG1 fusion oncogenes in lipoblastoma

Lipoblastomas are pediatric neoplasms resulting from transformation of adipocytes. These benign tumors are typically composed of adipose cells in different stages of maturation within a variably myxoid matrix, and they contain clonal rearrangements of chromosome band 8q12. Because lipoblastomas resemble embryonic adipose tissue, characterization of their transforming mechanisms might reveal biological pathways in physiological adipogenesis. Herein, we demonstrate that lipoblastoma chromosome 8q12 rearrangements bring about promoter-swapping events in the PLAG1 oncqgene. We show that the hyaluronic acid synthase 2 (HAS2) or collagen 1 alpha 2 (COL1A2) gene promoter regions are fused to the entire PLAG1 coding sequence in each of four lipoblastomas. PLAG1 is a developmentally regulated zinc finger gene whose tumorigenic function has been shown previously only in epithelial salivary gland cells. Our findings reveal that PLAG1 activation, presumably resulting from transcriptional up-regulation, is a central oncogenic event in lipoblastoma.

The cytogenetic and molecular characterization of benign and malignant soft tissue tumors

Cytogenetic analyses of benign and malignant soft tissue tumors have led to the description of recurrent, specific, and even pathognomonic chromosomal translocations and/or other rearrangements in most types of soft tissue tumors. The consistent karyotypic rearrangements have provided critical diagnostic information in this group of neoplasms that often presents significant diagnostic challenges to the clinician and the pathologist. These findings have also been instrumental in the characterization of the abnormalities at the molecular level. Novel genes have been isolated from the translocation junctions and the mechanisms of their deregulation identified. This has increased our understanding of the histogenesis of these tumors, paved the way for the molecular diagnosis of many sarcomas, aided in directing therapy, and also provided important prognostic information.

Expression of growth hormone receptor in human liposarcomas and lipomas

Our immunohistochemical results clearly demonstrated the occurrence of growth hormone receptors (GH-R) in the tumour cells of lipomas and liposarcomas. In liposarcomas staining intensity in the cytoplasm of tumour cells varied between weak and distinct but could not be correlated to the histological grade of the malignant tumours. These findings were corroborated to some extent by the RT-PCR results. RT-PCR analysis of human lipomas and liposarcomas revealed the amplified cDNA fragment of GH-R in 8 out of 12 lipomas but only in 3 out of 10 liposarcomas. The reduced number of GH-R positive tumours found with PCR may be explained by the extraction method of RNA from paraffin sections. An interesting finding was the distinct immunoreactivity of the endothelium of blood vessels in liposarcomas, which was especially pronounced in the newly forming capillaries. This points to an important role of GH-R in tumour angiogenesis which could significantly contribute to tumour growth in liposarcomas and may open the possibility for therapeutic intervention using antiangiogenic substances.