Mixed-type liposarcoma: clinicopathological, immunohistochemical, and molecular analysis of a case arising in deep soft tissues of the lower extremity

A Low-Grade Myxoid Liposarcoma Arising in a Deep-Seated Conventional Lipoma

Myxoid liposarcomas (MLS) are known to arise de novo and have not been shown to derive from previous benign lesions (lipomas), whereas lipomas occasionally harbor areas of other benign mesenchymal tissue. Rarely, tumors presenting with MLS or round cell liposarcomas together with conventional liposarcoma have been classified as mixed liposarcomas. However, no case of MLS arising in a conventional lipoma has been described. In this article, we report a case of a young male presenting with a deep-seated soft tissue tumor of the posterior part of the thigh. The tumor was removed en bloc. Grossing revealed a small encapsulated myxoid lesion (2.5 cm) within the larger lipomatous tumor (14 cm). Histological examination and cytogenetic analysis revealed a FUS-CHOP positive low-grade MLS arising in a conventional lipoma without histological atypia, FUS-CHOP fusion, or CDK4/MDM2 amplification. While we cannot conclude whether these were collision tumors or an MLS progression from a lipoma, this case highlights the value of careful grossing in the soft tissue setting.

Paratesticular dedifferentiated liposarcoma with prominent myxoid stroma: report of a case and review of the literature

Paratesticular sarcoma is rare, but liposarcoma is its most common type. Paratesticular liposarcoma sometimes presents as dedifferentiated liposarcoma. Both high-grade and low-grade dedifferentiation have been reported. Herein, we presented a unique case of a 64-year-old man with low-grade dedifferentiated liposarcoma with prominent myxoid stroma. Well-differentiated liposarcoma components extended along the spermatic cord. The constituent cells of the dedifferentiated component were peculiar in that, they were relatively uniform cells with atypia and did not have pleomorphism to such an extent that it mimicked myxofibrosarcoma. This myxoid component was confidently differentiated from myxoid liposarcoma with the help of immunohistochemical analysis using CDK4 and MDM2. These two markers were also expressed in the well-differentiated component. It could therefore be confirmed that this sarcoma is dedifferentiated liposarcoma but is not mixed-type liposarcoma comprising well-differentiated liposarcoma and myxoid liposarcoma.

Extensive lipoma-like changes of myxoid liposarcoma: morphologic, immunohistochemical, and molecular cytogenetic analyses

Myxoid liposarcomas (MLSs) with extensive lipoma-like changes (MLSLC) are rare, and it is often difficult to distinguish them from well-differentiated liposarcoma (LS)/dedifferentiated LS (WDLS/DDLS) with myxoid changes. For the characterization of these neoplasms, we studied 8 MLSLCs, 11 ordinary MLSs, 4 WDLSs, and 6 DDLSs. Cytogenetically, MLSLC and ordinary MLS were characterized by t(12;16)(q13;p11) and FUS-DDIT3 fusion gene, whereas WDLS/DDLS lacked the fusion gene but possessed giant marker/ring chromosomes. Both lipoma-like and myxoid components of the same MLSLC exhibited the identical FUS-DDIT3, as confirmed by fluorescence in situ hybridization (FISH) and reverse transcription polymerase chain reaction (RT-PCR). Immunohistochemically, MDM2 and CDK4 were positive in WDLS/DDLS but negative in MLSLC and ordinary MLS. PPARγ, C/EBPα, adipophilin, and perilipin were found in each type of LS. Adipophilin was expressed chiefly in tiny fat droplets of immature lipoblasts, whereas perilipin showed a strong positive staining in large fat vacuoles of signet ring and multivacuolated lipoblasts. The Ki-67 labeling index was lower in the lipoma-like component of MLSLC when compared with the myxoid component of the same tumors as well as ordinary MLS (p < 0.001). When compared with ordinary MLS, MLSLC may be less aggressive in clinical behavior (rare recurrences or metastases) after a wide surgical excision. In conclusion, the distinction between MLSLC and WDLS/DDLS is important, because of the differences of molecular cytogenetic features as well as clinical behaviors between these distinct sarcomas presenting similar morphologic features. In addition, the combined immunohistochemical detection of adipophilin and perilipin may provide a useful ancillary tool for identification of lipoblastic cells in soft tissue sarcomas.

Atypical lipomatous tumor of the cheek - a case report

Liposarcoma is the most common soft tissue malignant tumor. It mostly arises in the subcutaneous tissue of shoulders, limbs and neck, and retroperitoneal space, but head occurrence is very rare. Atypical lipomatous tumor (ALT) is a well-differentiated liposarcoma (WDLPS) and constitutes 40-45% of all liposarcoma cases. A case of 57-year-old woman with a tumor of the left cheek, causing a discreet face asymmetry is presented. The tumor was soft and caused no tenderness. The patient reported no previous injury of the region. Fine-needle aspiration biopsy (FNAB) revealed atypical cells suspected of liposarcoma. MR examination showed fascicles of adipose tissue, which made the left cheek prominent. The patient was operated under general anaesthesia. Adipose tissue of the left cheek was removed. Postoperative course was uneventful. The final histopathological diagnosis - was atypical lipomatous tumor/well-differentiated liposarcoma (ALT/WDLPS). The patient remains under laryngological care. No recurrence of the disease has been observed during the 5 years follow-up.

Primary dedifferentiated liposarcoma of the axilla arising in a mixed, well-differentiated and myxoid liposarcoma

We describe a case of mixed liposarcoma of the axilla presenting as a high grade undifferentiated sarcoma with areas of well-differentiated and myxoid liposarcoma. MRI demonstrated a lobulated, septated intermuscular mass with marked heterogeneous gadolinium enhancement. A small focus of the tumor demonstrated fat suppressed signal more characteristic of well-differentiated liposarcoma. Pathologic analysis following wide local excision revealed a large, high grade sarcomatous component with highly pleomorphic cells with a thin rim of well-differentiated and myxoid liposarcoma on histologic examination. Dedifferentiated liposarcomas arising outside of the retroperitoneum are very rare, as are dedifferentiated liposarcomas arising from a histologically mixed liposarcoma. In this regard, this case illustrates an unusual combination of tumor location and histology which, to our knowledge, has not previously been reported.

The expanded histologic spectrum of myxoid liposarcoma with an emphasis on newly described patterns: implications for diagnosis on small biopsy specimens

The variety of histologic patterns in myxoid liposarcoma is underappreciated. The diversity of these patterns can lead to diagnostic difficulty. We examined the morphologic spectrum of myxoid liposarcoma by cataloguing and describing different patterns identified in biopsy and resection specimens of 46 primary, recurrent, and metastatic myxoid liposarcomas. The patterns identified in the 46 cases included traditional myxoid (43 [93%]), traditional round cell (17 [37%]), pseudoacinar (24 [52%]), lipoblast-rich (13 [28%]), island (11 [24%]), lipomatous (10 [22%]), stromal hyalinization (7 [15%]), cord-like (5 [11%]), nested (3 [7%]), chondroid metaplasia (2 [4%]), and hemangiopericytoma (HPC)-like (1 [2%]). Island and nested patterns had not previously been described. The diagnosis of myxoid liposarcoma was confirmed by fluorescence in situ hybridization studies for DDIT3 (also known as CHOP) rearrangement. The morphologic spectrum of myxoid liposarcoma spans well beyond its typical appearance of spindle cells in a myxoid stroma with a prominent vascular pattern. Awareness of the variety of histologic patterns is critical to avoid misdiagnosis, especially in small biopsy specimens.

Well-circumscribed deep-seated lipomas of the upper extremity. A report of 13 cases

BACKGROUND

The purpose of this study is to determine if giant size is of bad prognosis in deep lipomas of the upper extremity.

PATIENTS AND METHODS

We report a retrospective study of 13 patients with deep-seated lipomas of the upper extremity treated during the period from April 1997 to April 2008. We evaluated the clinical and radiological characteristics, treatment and evolution profile of these patients.

RESULTS

There were 10 women and three men, with an average age of 53 years (range 30-79 years). Seven of these lipomas were in the arm, one in the shoulder, and five in the forearm. Six lipomas were intramuscular, six intermuscular (three of them being attached to bone and labelled parosteal lipoma) and one epivaginal lipoma of the flexor tendon sheath. All patients presented a progressive slow-growing mass that was associated with radial paralysis in one case and carpal tunnel syndrome in one case. Plain radiographs showed a radiolucent soft-tissue image in all cases and an associated osteochondroma in one parosteal lipoma. Computer tomography (CT) or magnetic resonance imaging (MRI) suggested the lipomatous nature and benign characteristics of these deep lipomas that were giant in all cases (mean size: 7 cm). Lipoma marginal excision was performed and histopathological examination demonstrated features consistent with a benign lipoma. There was good function and no clinical recurrence was observed after a mean follow-up of three years.

DISCUSSION

Giant deep-seated lipomas of the upper extremity are uncommon and can be intermuscular or intramuscular. A painless soft-tissue mass is the most frequent chief complaint. MRI with fat suppression suggests the diagnosis and studies the extension of deep lipoma. Marginal excision is the treatment of choice and histopathology eliminates diagnosis of well-differentiated liposarcoma.

CONCLUSION

Appropriate evaluation of deep lipoma is to rule out malignancy by systematically performing MRI and biopsy. In contrast to deep-seated lipomas of the lower extremity or the retroperitoneal space, the prognosis of deep-seated lipomas of the upper extremity is good irrelevant of their size. Recurrence and the degeneration are very rare.

LEVEL OF EVIDENCE

Level 4.

Oncogenesis and classification of mixed-type liposarcoma: a radiological, histopathological and molecular biological analysis

Liposarcomas are separated into clinicopathological entities with a characteristic morphological spectrum and mutually exclusive genetic alterations. Therefore, the rare occurrence of cases with combined patterns of well-differentiated liposarcoma and myxoid liposarcoma designated as mixed-type liposarcoma pose a conceptual problem. Moreover, this feature may have consequences for treatment choice and prognosis. Here, we have dissected the molecular relation of tumor components in cases of mixed-type liposarcoma. On the basis of heterogeneous preoperative magnetic resonance image (MRI) features, eight cases of mixed-type liposarcoma were selected. Preoperative biopsy samples and resection specimens were analyzed including molecular and immunohistochemical analysis on all components. As controls, cases with homogeneous MRI features and uniform aspects of myxoid liposarcoma (n = 5), round cell liposarcoma (n = 5) and well-differentiated liposarcoma (n = 5) were studied. All patients with heterogeneous MRI features showed morphological components of myxoid liposarcoma and well-differentiated liposarcoma. Real-time polymerase chain reaction showed FUS-DDIT3 fusion in both components in five of eight cases in the absence (zero of five) of MDM2 and CDK4 amplification. In three of eight patients, MDM2 and/or CDK4 were overexpressed, and amplification was shown by multiplex ligation-dependent probe amplification (MLPA) in the absence of myxoid liposarcoma translocations. All control patients showed a molecular pattern consistent with their morphological features. Therefore, mixed-type liposarcomas should not be regarded as collision tumors, but as an extreme variant of the morphological spectrum within a single biological entity, explaining the biological contradiction of mixed-type liposarcoma. For treatment stratification, detailed classification including molecular support should be performed in tumors with heterogeneous MRI features.

Contributions of cytogenetics and molecular cytogenetics to the diagnosis of adipocytic tumors

Over the last 20 years, a number of tumor-specific chromosomal translocations and associated fusion genes have been identified for mesenchymal neoplasms including adipocytic tumors. The addition of molecular cytogenetic techniques, especially fluorescence in situ hybridization (FISH), has further enhanced the sensitivity and accuracy of detecting nonrandom chromosomal translocations and/or other rearrangements in adipocytic tumors. Indeed, most resent molecular cytogenetic analysis has demonstrated a translocation t(11;16)(q13;p13) that produces a C11orf95-MKL2 fusion gene in chondroid lipoma. Additionally, it is well recognized that supernumerary ring and/or giant rod chromosomes are characteristic for atypical lipomatous tumor/well-differentiated liposarcoma and dedifferentiated liposarcoma, and amplification of 12q13–15 involving the MDM2, CDK4, and CPM genes is shown by FISH in these tumors. Moreover, myxoid/round cell liposarcoma is characterized by a translocation t(12;16)(q13;p11) that fuses the DDIT3 and FUS genes. This paper provides an overview of the role of conventional cytogenetics and molecular cytogenetics in the diagnosis of adipocytic tumors.