[Fourth edition of WHO classification tumours of soft tissue]. / Quatrième édition de la classification OMS des tumeurs des tissus mous.

The new World Health Organization (WHO) classification of soft tissue tumours was published in 2013, 11years after the previous edition. This new classification includes several changes: newly included sections (gastrointestinal stromal tumors…), newly recognized entities (pseudomiogenic haemangioendothelioma, haemosiderotic fibrolipomatous tumour…), and new genetic and molecular data leading to better understanding and definition of tumours, and are useful as diagnostic tools. This brief review summarizes changes in this new edition of the WHO classification of tumours of soft tissue.

[Adipocytic tumors]. / Tumeurs adipeuses.

Adipocytic tumors are the most common mesenchymal neoplasms, liposarcoma accounting for approximately 20% of soft tissue sarcomas. The differential diagnosis between benign and malignant tumors is often problematic and represents a significant proportion of consultation cases. The goal of this article is to review liposarcoma subtypes, the main benign adipocytic neoplasms: lipoblastoma, hibernoma, spindle/pleomorphic cell lipoma, chondroid lipoma, as well as non adipocytic neoplasms with a lipomatous component such as lipomatous solitary fibrous tumor, emphasizing on practical differential diagnosis issues, and immunohistochemical and molecular tools allowing their resolution.

Atypical lipomatous tumor/well-differentiated liposarcoma: what is it?

Liposarcoma (LPS) is the most common soft tissue sarcoma, frequently found in the thigh and retroperitoneum. LPS is commonly classified into well-differentiated LPS and dedifferentiated LPS. Histologic subtype, tumor location, and completeness of surgical resection are important prognostic indicators for LPS. Magnetic resonance imaging best characterizes extremity lesions, whereas computed tomography is most often used for intra-abdominal and retroperitoneal tumors. Surgical resection is the mainstay of treatment. Adjuvant radiation is considered for close margins. Survival for extremity tumors is favorable. However, difficulty in obtaining wide margins in the retroperitoneum predisposes to local recurrence and, ultimately, death from unresectable disease.

Benign fatty tumors: classification, clinical course, imaging appearance, and treatment.

Lipoma is the most common soft-tissue tumor, with a wide spectrum of clinical presentations and imaging appearances. Several subtypes are described, ranging from lesions entirely composed of mature adipose tissue to tumors intimately associated with nonadipose tissue, to those composed of brown fat. The imaging appearance of these fatty masses is frequently sufficiently characteristic to allow a specific diagnosis. However, in other cases, although a specific diagnosis is not achievable, a meaningful limited differential diagnosis can be established. The purpose of this manuscript is to review the spectrum of benign fatty tumors highlighting the current classification system, clinical presentation and behavior, spectrum of imaging appearances, and treatment. The imaging review emphasizes computed tomography (CT) scanning and magnetic resonance (MR) imaging, differentiating radiologic features.

From the archives of the AFIP: benign musculoskeletal lipomatous lesions.

Benign lipomatous lesions involving soft tissue are common musculoskeletal masses that are classified into nine distinct diagnoses: lipoma, lipomatosis, lipomatosis of nerve, lipoblastoma or lipoblastomatosis, angiolipoma, myolipoma of soft tissue, chondroid lipoma, spindle cell lipoma and pleomorphic lipoma, and hibernoma. Soft-tissue lipoma accounts for almost 50% of all soft-tissue tumors. Radiologic evaluation is diagnostic in up to 71% of cases. These lesions are identical to subcutaneous fat on computed tomographic (CT) and magnetic resonance (MR) images and may contain thin septa. Lipomatosis represents a diffuse overgrowth of mature fat affecting either subcutaneous tissue, muscle or nerve, and imaging is needed to evaluate lesion extent. Lipoblastoma is a tumor of immature fat occurring in young children, and imaging features may reveal a mixture of fat and nonadipose tissue. Angiolipoma, myolipoma, and chondroid lipoma are rare lipomatous lesions that are infrequently imaged. Spindle cell and pleomorphic lipoma appear as a subcutaneous lipomatous mass in the posterior neck or shoulder, with frequent nonadipose components. Hibernoma appears as a lipomatous mass with serpentine vascular elements. Benign lipomatous lesions affecting bone, joint, or tendon sheath include intraosseous lipoma, parosteal lipoma, liposclerosing myxofibrous tumor, discrete lipoma of joint or tendon sheath, and lipoma arborescens. Intraosseous and parosteal lipoma have a pathognomonic CT or MR appearance, with fat in the marrow space or on the bone surface, respectively. Liposclerosing myxofibrous tumor is a rare intermixed histologic lesion commonly located in the medullary canal of the intertrochanteric femur. Benign lipomatous lesions may occur focally in a joint or tendon sheath or with diffuse villonodular proliferation in the synovium (lipoma arborescens) and are diagnosed based on location and identification of fat. Understanding the spectrum of appearances of the various benign musculoskeletal lipomatous lesions improves radiologic assessment and is vital for optimal patient management.

Hibernoma: presentación de 2 casos / Hybernoma: report of 2 cases

El hibernoma es una neoplasia benigna originada del tejido adiposo inmaduro. Presentamos 2 casos, los cuales tuvieron localización supraclavicular. El cuadro histológico de ambos correspondió a la variante típica de hibernoma, subtipo de células eosinófilas. Clínicamente debe efectuarse diagnóstico deferencial con el lipoma, angiolipoma y en ocasiones con el liposarcoma bien diferenciado. Los avances en citogenética mostraron que existe una traslocación en la región 11q 13-21. El tratamiento de elección es la resección quirúrgica (AU)

Mesenchymal, non-meningothelial tumors of the central nervous system.

The spectrum of non-meningothelial mesenchymal tumors that may arise within the central nervous system is presented, based on the current classification of soft tissue tumors. Among malignant types, hemangiopericytoma, rhabdomyosarcoma, mesenchymal chondrosarcoma, and malignant fibrous histiocytoma are the most frequent ones. Rare tumor entities are mentioned. As in soft tissue sarcomas, diagnosis is mainly based on light and electron microscopy, while immunohistochemistry can improve accuracy of diagnosis.