Myosarcoma, malignant rhabdomyoma, rhabdomyosarcoma, rhabdopoietic sarcoma, rhabdosarcoma, embryonal sarcoma. Rhabdomyoblastoma, rhabdomyopoietic sarcoma, monomorphous round cell rhabdomyosarcoma. Intravascular bronchioloalveolar tumor, angioglomoid tumor, myxoid angioblastomatosis. Lymphangiosarcoma, hemangiosarcoma, hemangioblastoma, malignant hemangioendothelioma, malignant angioendothelioma.
Tendosynovial sarcoma, synovial cell sarcoma, malignant synovioma, synovioblastic sarcoma. MRI of dedifferentiated liposarcoma top row obtained using coronal T2WI with fat-suppression and T1WI after contrast administration; myxoid liposarcoma middle row obtained using axial T1WI before and after contrast administration; pleomorphic liposarcoma bottom row obtained using axial T1WI before contrast administration and T1WI with fat-suppression after contrast administration.
For sites of involvement darker gray indicates higher frequency. RP retroperitoneum. Myxoid liposarcomas are the second most common subtype of liposarcoma and they occur mainly in young adults, often in the deep soft tissues of the thigh. Macroscopically myxoid liposarcomas are well-circumscribed, multinodular, intramuscular tumors without prominent tumor necrosis. Myxoid liposarcomas often recur and metastasize to unusual locations such as the RP and the opposite extremity, even before spreading to the lungs [ 1 , 5 ]. Tumors have a high SI on T2WI, due to the myxoid matrix, and most show heterogeneous enhancement with nonenhancing areas of mucinous material and enhancing areas with high vascularity and cellularity [ 7 , 8 , 9 , 11 ].
Some present as cystic masses with sharply demarcated margins, which can lead to misdiagnosis as a benign cyst. However, after contrast administration these tumors show a solid area with intense enhancement [ 12 ]. The round cell highly cellular variant has a nonspecific heterogeneous appearance Fig.
Pleomorphic liposarcomas are the least common subtype of liposarcoma and they occur in elderly patients, mainly in the deep soft tissues of the extremities. On MRI pleomorphic liposarcomas are difficult to differentiate from other aggressive sarcomas because they present as heterogeneous masses low on T1WI, high on T2WI, with heterogeneous enhancement and because they contain little or no fat.
They usually show well-circumscribed margins [ 7 , 8 , 9 ] Fig. Adult fibrosarcoma is no longer considered a separate entity and is therefore not included in this discussion. Low grade fibromyxoid sarcoma middle row images courtesy of Dr. Low grade fibromyxoid sarcomas occur in the proximal extremities or trunk of young to middle-aged adults.
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Typically these sarcomas are well-circumscribed masses without hemorrhage or necrosis [ 5 ]. Histologically the tumors consist of bland spindle-shaped cells in a variably fibrous and myxoid stroma, alternating in different areas of the tumor [ 1 , 5 ], resulting in slightly inhomogeneous masses with intermediate SI on T1WI and high SI on T2WI.
De Schepper et al. Koh et al. One was well circumscribed with multiple intralesional nodules, some with a target-like appearance, the other showed invasive features without multinodularity. Both showed heterogeneous contrast enhancement [ 16 ] Fig. Sclerosing epithelioid fibrosarcomas are rare sarcomas of fibroblastic nature simulating poorly differentiated carcinoma or sclerosing lymphoma. The main sites of involvement are the lower extremities and limb girdle. Tumors can contain myxoid, cystic, and calcified areas but necrosis is uncommon [ 1 , 5 ].
These tumors can present as a painful mass. Christensen et al.
Histology at a Glance
UPS undifferentiated pleomorphic sarcoma, RP retroperitoneum. Alveolar rhabdomyosarcomas are primitive, malignant, round cell neoplasms that show partial skeletal muscle differentiation. Alveolar rhabdomyosarcomas commonly arise in the extremities but have no real favored site of origin. Alveolar rhabdomyosarcomas contain fibrovascular septa that separate the tumor into nests accounting for their alveolar appearance [ 22 ]. They present as infiltrative, expansile, soft tissue masses, characterized by multiple areas of necrosis [ 10 ].
High flow vessels can be seen, as well as a lobular appearance after contrast administration, but other signal characteristics are nonspecific [ 20 ] Fig. Pleomorphic rhabdomyosarcomas are high grade sarcomas consisting of bizarre cells which display evidence of muscle differentiation. In contrast to the other subtypes pleomorphic rhabdomyosarcomas occur almost exclusively in adults, mainly in the deep soft tissues of the extremities.
Pleomorphic rhabdomyosarcomas contain variable amounts of hemorrhage and necrosis [ 1 , 5 ]. Necrotic foci are readily identifiable in many cases [ 1 ]. Pleomorphic rhabdomyosarcomas have been shown to present with areas of necrosis alternating with areas of marked enhancement and areas of ring-like enhancement around areas of low SI [ 10 ] Fig. Vilanova et al. Soft tissue angiosarcomas AS are malignant tumors containing cells with morphologic and functional features of endothelial cells.
AS generally contain both epithelioid and spindle cell areas, forming rudimentary infiltrating vascular channels. Hemorrhage is common and often extensive. AS present as enlarging masses with or without systemic symptoms such as coagulopathy, anemia, hematomas, and bruisability. SI on T2WI may reflect the relative proportion of vascular space, cellularity, and stroma in the tumor [ 24 , 25 , 26 ] Fig. Clear cell sarcomas of soft tissue are tumors with melanocytic differentiation, typically involving tendons and aponeuroses. The principal sites of involvement are the extremities, mainly the foot and ankle.
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These tumors occur mainly in young adults. Histologically clear cell sarcomas of soft tissue present with a uniform, nested, or fascicular growth pattern with thin fibrous septa delineating the tumor cell nests. Differentiation from malignant melanoma is impossible on morphological grounds [ 1 , 5 ]. Hourani et al. As clear cell sarcomas are often well-defined and homogeneous and rarely show bone destruction or necrosis, they are often misdiagnosed as benign lesions [ 10 , 31 , 33 , 34 , 35 , 36 ] Fig.
Epithelioid sarcomas are tumors of unknown lineage with predominantly epithelioid cytomorphology. They may be misdiagnosed as benign granulomatous processes such as rheumatoid nodules. Macroscopically these tumors are small ill-defined dermal or subcutaneous nodules or larger deeper masses involving tendons or fascia. The center of these sarcomas is usually necrotic or hemorrhagic.
The main sites of involvement are the flexor surfaces of the hand and forearm. Epithelioid sarcomas occur mainly in young adults. Epithelioid sarcomas are reported to be homogeneous or heterogeneous depending on their location superficial: homogeneous, deep: heterogeneous and they are mostly isointense to muscle on T1WI and hyperintense on T2WI with strong enhancement [ 10 , 33 ]. Chao et al.
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Calcifications were present but not visible on MRI [ 37 ]. Zevallow-Gieampietri et al. The first tumor was a well-circumscribed mass with homogeneous enhancement. The second tumor was a nonencapsulated tumor, showing heterogeneous enhancement involving subcutaneous tissue and muscle tissue. Neither tumor showed calcifications or bone or skin involvement [ 38 ] Fig. Alveolar soft part sarcomas ASPS are tumors with a high vascularity causing pulsations or bruits over the tumor. The main sites of involvement are the extremities. ASPS mainly occur in young adults. In addition, equipment for the preparation of tissue slices for live recording is available.
Embedding of tissue specimens in paraffin wax for subsequent microtome sectioning. Used in conjunction with the Leica RM microtome. Capable of sectioning relatively hard materials. Rapid specimen freezing.
Tissue is then removed from the processing machine and is infiltrated with fresh molten paraffin, oriented, and allowed to cool and harden into a block. Tissue can then be sectioned on a microtome and slides produced.
Many antigens and RNA do not survive routine histological processes. An alternative method requires tissue to be frozen and sectioned in a cryostat. Antigen preservation is always superior in fresh frozen tissue. Unfortunately, the drawback to frozen sections is the vastly inferior morphology of the tissue.
Tissue can be dissected, placed in a disposable mold which has been labeled as previously discussed, immersed in OCT a freezing medium and flash frozen in a bath of dry ice and liquid nitrogen. Once again, orientation must be considered prior to freezing the tissue. We can help you determine the best method to demonstrate the particular antigen in a specific tissue.
The facility has available a Thermo automated microtome and tungsten carbide blade used in sectioning resin embedded tissue for the light microscope. The reagents used are glycomethacrylate resins that produce a firmer medium, allowing thinner 2 micron sections to be cut.
It is particularly useful for undecalcified bone. The disadvantages to this method involve the toxicity of the reagents and the limited stains that are compatible with the resin. At this time, we do not process or embed tissue in resin, but we are able to section this material after you process and embed it. We can help you decide on appropriate stains for use with resin-embedded tissue. The Koch Institute has an affiliation with Dr.
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Roderick Bronson, a veterinary pathologist at Harvard Medical School. He is available to consult with investigators on most Fridays. Appointments are requested through iLab Schedule Resources tab. We hope this brief overview will be helpful in getting you started with histology. If you have other concerns or issues you would like to discuss or if you would to observe the histology operation, please feel free to contact us at X