Soft Tissue Tumors - Malignant fibrous histiocytoma of soft tissue

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Soft Tissue Tumors

Fibrohistiocytic tumors

Malignant fibrous histiocytoma of soft tissue - inflammatory

Reviewer: Vijay Shankar, M.D. (see Reviewers page)
Revised: 28 October 2012, last major update August 2012
Copyright: (c) 2003-2012, PathologyOutlines.com, Inc.

General
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● Neoplastic histiocyte-like cells mixed with, and often obscured by neutrophils and other inflammatory cells

Terminology
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● Most of these tumors are probably dedifferentiated liposarcoma (J Pathol 2004;203:822, see also Pathol Int 1997;47:642) or leiomyosarcoma
● Diagnosis of exclusion; recommended to take many sections and use immunohistochemistry to rule out mimics

Clinical features
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● Very rare, usually age 40+ years, often retroperitoneal
● May be associated with fever, leukocytosis (leukemoid reaction) and eosinophilia
● May occur in skin with predominance of lymphocytes (Am J Dermatopathol 2002;24:251)
● Very aggressive with poorest prognosis of all MFH types (2/3 die of disease, 1/4 have distant metastases) although these studies probably included other morphologically similar disorders

Case reports
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● 4 year old boy with chest wall swelling (Fetal Pediatr Pathol 2004;23:319)
● 45 year old woman with kidney tumor (Pathol Res Pract 2008;204:857)
● 46 year old man with tumor originating in thymus (Ann Thorac Surg 2010;89:2003)
● 63 year old man with abdominal tumor (Case of the Week #144)
● 65 year old woman with lumbar abscess (Case Rep Oncol 2011;4:343)

Gross description
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● 8-10 cm, yellow due to xanthoma cells; firm, lobulated

Micro description
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● Commonly has storiform pattern, background of inflammatory cells (histiocyte-like, xanthoma, neutrophils, lymphocytes, eosinophils, plasma cells) which may obscure tumor cells
● Tumor cytoplasm may contain phagocytized neutrophils; nuclei are large and vesicular with prominent nucleoli
● May have bizarre giant cells or atypical mitotic figures but no necrosis

Micro images
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Acute inflammatory cells and large histiocyte-like cells

Large histiocyte-like cells with prominent nucleoli resembling lymphoma or carcinoma, with variable fibroblasts

Numerous histiocyte-like cells resembling lymphoma

Associated with orthopedic implant

Case of week #144 - abdominal tumor

H&E, CD68, vimentin

Cytology description
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● Neutrophilic infiltrate in and around tumor cells, which show prominent neutrophilic phagocytosis (Fetal Pediatr Pathol 2004;23:319)

Positive stains
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● MDM2, CDK4 (these cases may actually be dedifferentiated liposarcoma), a1-antitrypsin
● Alpha 1 antitrypsin (Ann Thorac Surg 2010;89:2003)

Molecular / cytogenetics description
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● 12q13-15 amplification or gain (these cases may actually be dedifferentiated liposarcoma)

Differential diagnosis
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● Myxoid or dedifferentiated liposarcoma: may need to submit additional sections of normal appearing fat to identify, perform MDM2 or CDK4 or obtain cytogenetics)
● Hodgkin lymphoma or anaplastic lymphoma (Mod Pathol 1997;10:438)
● Inflammatory myofibroblastic tumor
● Melanoma
● Metastatic renal or adrenal carcinoma
● Osteosarcoma-irradiated: malignant osteoid present
● Reactive abscess-like lesion
● Xanthogranulomatous pyelonephritis : no malignant component, only reactive (Int J Urol 2006;13:1000)

End of Soft Tissue Tumors > Fibrohistiocytic tumors > Malignant fibrous histiocytoma of soft tissue - inflammatory

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