[Lipoma and atypical lipomatous tumor within the same neoplasia: Evidence for a continuous transition]

MDM2 amplification in rod-shaped chromosomes provides clues to early stages of circularized gene amplification in liposarcoma

Well-differentiated liposarcoma (WDLS) displays amplification of genes on chromosome 12 (Chr12) in supernumerary ring or giant marker chromosomes. These structures have been suggested to develop through chromothripsis, followed by circularization and breakage-fusion-bridge (BFB) cycles. To test this hypothesis, we compared WDLSs with Chr12 amplification in rod-shaped chromosomes with WDLSs with rings. Both types of amplicons share the same spectrum of structural variants (SVs), show higher SV frequencies in Chr12 than in co-amplified segments, have SVs that fuse the telomeric ends of co-amplified chromosomes, and lack interspersed deletions. Combined with the finding of cells with transient rod-shaped structures in tumors with ring chromosomes, this suggests a stepwise process starting with the gain of Chr12 material that, after remodeling which does not fit with classical chromothripsis, forms a dicentric structure with other chromosomes. Depending on if and when telomeres from other chromosomes are captured, circularized or linear gain of 12q sequences will predominate.

Resection of liposarcoma of the greater omentum: A case report and literature review

INTRODUCTION

Liposarcoma usually occurs in the retroperitoneum and limbs. Liposarcoma of the greater omentum is rare, and most information of such liposarcomas has come from case reports.

PRESENTATION OF CASE

A 60-year-old woman was found to have an 8-cm intra-abdominal mass (suspected lipoma) by computed tomography. At the age of 63 years, she underwent a medical examination and a mass was palpated in the abdomen. Contrast-enhanced computed tomography and magnetic resonance imaging confirmed the presence of a huge intra-abdominal tumor with the omental artery passing through the mass. The tumor was simply resected. Histopathologically, the tumor was diagnosed as a well-differentiated liposarcoma, and the resection margin was microscopically negative. The patient had developed no recurrence or complications 9 months postoperatively.

DISCUSSION

Liposarcoma of the greater omentum is rare, and differentiation of liposarcoma from other tumors is challenging. Adjuvant therapy has not been established as an effective treatment, and radical (R0) resection of the tumor is recommended. Our case of liposarcoma of the greater omentum was surgically managed with good outcomes.

CONCLUSION

The diagnosis of liposarcoma with a lipomatous tumor is challenging, and resection should be considered for huge intra-abdominal lipomatous tumors.

Atypical lipomatous tumors/well-differentiated liposarcomas: clinical outcome of 67 patients

Atypical lipomatous tumors/well-differentiated liposarcomas are low-grade malignant mesenchymal neoplasms with high propensity to local recurrence and potential to dedifferentiate to higher grades over time. However, the published risks of local recurrence and dedifferentiation vary, and no unified treatment and follow-up plan has been accepted. We performed a study to evaluate the long-term clinical behavior and proper treatment and follow-up strategy for these tumors. We retrospectively reviewed the files of 101 patients treated between 1990 and 2008 with the diagnosis of atypical lipomatous tumors/well-differentiated liposarcomas. For 67 of these patients, complete data and 2-year minimum follow-up were available and were included in the study; 47 patients (group A) had primary surgical treatment at our institution and 20 patients (group B) were referred after ≥1 local recurrences. Mean follow-up was 81 months (range, 24-229 months). The local recurrence rate of primary atypical lipomatous tumors/well-differentiated liposarcomas was 10.6% (5/47 group A patients). The local re-recurrence rate of the recurrent atypical lipomatous tumors/well-differentiated liposarcomas was 52% (13/67 group A and B patients). Recurrences developed as late as 140 months after diagnosis and treatment. The rate of dedifferentiation at recurrences was 4% (1/25 group A and B patients with recurrent tumors). No patients developed metastases. Atypical lipomatous tumors/well-differentiated liposarcomas are associated with an increased rate of local re-recurrence and low risk of dedifferentiation at recurrences. Long-term follow-up is recommended for early diagnosis and treatment of local recurrences.

[Atypical lipomatous tumors of the stomach. Clinical, morphological and molecular findings]

Two cases of primary gastric atypical lipomatous tumors (ALT) are presented. In case No.1, a 7x4x3 cm submucosal ALT (lipoma-like subtype) of the antrum/pyloric region in a 60-year-old woman was completely resected. Using interphase dual-color-FISH, MDM2- and CDK4 amplifications could be detected in distinguished amplicons. The patient was continuously free of disease after 56 months. In case No. 2, a 3.5 cm (in diameter) submucosal ALT (lipoma-like subtype) of the gastric body in a 56-year-old woman was completely resected. FISH revealed MDM2 amplification while the CDK4 gene remained in diploid copies. This patient was continuously free of disease after 36 months. The morphologic and molecular biological findings of this rare primary gastric mesenchymal tumor are discussed in comparison with the corresponding soft tissue lesions.