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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.


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


● 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

● 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

● 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

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

Micro description

● 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

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

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

Positive stains

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

Molecular / cytogenetics description

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

Differential diagnosis

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
● 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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