Published online by Cambridge University Press: 01 March 2011
Myxomas encompass a heterogeneous group of clinicopathologic entities, common to which is prominent content of extracellular mucin. Soft tissue myxomas are fibroblastic-myofibroblastic neoplasms, or in some cases possibly non-neoplastic proliferations.
Cardiac myxoma is thought to originate from primitive, multipotential endocardial cells. In addition to myxomas, ossifying fibromyxoid tumor, a mesenchymal tumor of uncertain histogenesis with potentially malignant variants, is discussed in this chapter.
Common to all myxomas is the production of a mucoid intercellular substance by the fibroblastic or myofibroblastic tumor cells. Although the chemical composition of the mucins is known to vary, its analysis is not of great practical significance. The constituents include glycoproteins and proteolgycans that include neutral and acidic carbohydrate components, such as hyaluronic acid.
The apparent character of the mucoid material on hematoxylin and eosin (HE) stain depends not only on its composition but also on fixation and staining. The mucinophilic (metachromatic) quality of HE stains varies. Mucin also becomes progressively extracted into the fixative over time, and therefore specimens kept longer in the fixative typically lose mucins and the stain is less metachromatic.
INTRAMUSCULAR MYXOMA
Clinical Features
This relatively rare tumor typically presents in middle-aged adults between 40 and 70 years, with a 2:1 female predominance (Fig. 11.1). Nearly one half of the lesions occur in the thigh, with the arm and buttocks being other common locations. A wide variety of extremity locations and chest wall are among other possible sites (Fig. 11.2).
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