Myxoid variant of malignant fibrous histiocytoma

Authors

  • Sharon Whelan Weiss MD,

    1. Department of Soft Tissue Pathology, Armed Forces Institute of Pathology, Washington, DC, and the Johns Hopkins University Medical School, Baltimore, MD. Currently, Associate Pathologist, Department of Soft Tissue Pathology. Armed Forces Institute of Pathology Washington, D.C.
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    • Assistant Professor, Department of Pathology, Johns Hopkins University and Medical School, Baltimore, MD.

  • F. M. Enzinger MD

    Corresponding author
    1. Department of Soft Tissue Pathology, Armed Forces Institute of Pathology, Washington, DC, and the Johns Hopkins University Medical School, Baltimore, MD. Currently, Associate Pathologist, Department of Soft Tissue Pathology. Armed Forces Institute of Pathology Washington, D.C.
    • Armed Forces Institute of Pathology, Washington, DC 20306
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    • Department of Soft Tissue Pathology, Armed Forces Institute of Pathology, Washington, DC.


Abstract

It has not been generally recognized that malignant fibrous histiocytoma (MFH) may assume a highly myxoid, hypocellular appearance. Eighty cases of malignant fibrous histiocytoma having varying degrees of myxoid change were reviewed. These tumors typically arose on the extremities (leg, 61%; arm, 21%) of adults (peak age incidence, 60–69 years). They were usually attached to fascia (31%) or involved skeletal muscle (51%) and had a mucoid or translucent appearance. The myxoid areas consisted of widely spaced spindled and pleomorphic cells embedded in a matrix of acid mucopolysaccharides. The cellular areas were indistinguishable from those of the typical pleomorphic MFH. The rate of local recurrence of these tumors was 61%, and of metastasis, 23%, but metastasis was less likely when the tumor was small, superficially located, or had a prominent myxoid component. In fact, the degree of myxoid change was inversely related to the rate of metastasis. Therefore, because of the more favorable prognosis of the myxoid variant, it seems appropriate to separate it from the usual nonmyxoid form of MFH. The myxoid variant must also be clearly distinguished from benign myxoid lesions such as myxoma or nodular fasciitis, with which it is often confused.

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