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Soft tissue Tumors

Fibroblastic / myofibroblastic tumors

Hemangiopericytoma


Reviewers: Komal Arora, M.D., Vijay Shankar, M.D. (see Reviewers page)
Revised: 21 February 2013, last major update November 2012
Copyright: (c) 2003-2013, PathologyOutlines.com, Inc.

See variants below: infantile / congenital   lipomatous   phosphaturic mesenchymal tumor

General
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● Rare, controversial entity
● In soft tissue, most lesions are actually solitary fibrous tumor, monophasic synovial sarcoma or myofibromatosis (Am J Surg Pathol 2010;34:777)
● Diagnosis of exclusion (Histopathology 2006;48:63)
● Historically defined as lesions with thin walled, branching vascular pattern, although this pattern is common in many lesions
● Probably not a lesion of pericytes (cells arranged around capillaries and venules), except at sinonasal location
● See also discussions in these chapters: Bone, Breast, CNS, Heart, Nasal cavity, Thyroid gland

Clinical features
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● Slowly enlarging painless mass of middle aged adults, more common in women
● Most common in deep soft tissue, particularly pelvic retroperitoneum, also limb or limb girdles and head and neck
● Occasionally associated with hypoglycemia (J Clin Endocrinol Metab 1996;81:919)
● 20-50% metastasize to lungs, liver, bone
● 5 year survival was 86% in 2002 (Cancer 2002;95:1746)
● 70% have benign behavior
● Poor prognostic factors may be 4+ mitotic figures/10 HPF, necrosis, nuclear pleomorphism with size > 5 cm

Case reports
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● 4 year old boy with painless jaw mass (J Dent Child (Chic) 2010;77:180)
● 34 year old man with tongue lesion (Braz J Otorhinolaryngol 2012;78:136)
● 37 year old woman with rectal mass (J Med Case Rep 2011;5:352)
● 54 year old woman (Acta Otorhinolaryngol Ital 2011;31:194)
● 61 year old man with omental tumor with metastases (World J Surg Oncol 2007;5:63)
● 70 year old man with spontaneous rupture of cystic splenic tumor (Int J Emerg Med 2011;4:13)

Clinical images
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Jaw mass
Tongue lesion

Gross description
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● Well circumscribed, gray/white to red/brown cut surface, fleshy or spongy with hemorrhage, cystic degeneration, variable necrosis, up to 15 cm

Gross images
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Patient with 3 tumors:

(a) Greater omentum tumor (under forceps)
(b) Small jejunal tumor
(c) Retroperitoneal tumor with portions of diaphragm and liver
Encapsulated omental tumor

Micro description
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● Uniformly cellular (similar to cellular areas of solitary fibrous tumor) with numerous, variably ectatic or compressed, thin walled branching vessels with gaping sinusoidal spaces (staghorn configuration)
● Tumor cells are spindled to round with small amounts of pale or eosinophilic cytoplasm, indistinct margins, bland vesicular nuclei
● May have extensive fibrosis, hyalinization, myxoid change
● Variable mitotic activity
● No atypia

Micro images
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Staghorn vessels and spindle cells
Various images (many from CNS)
Staghorn vessels are prominent
Reticulin stain
Jaw mass
Various images
Rectal mass
Reticulin
Gomori methinamine silver

Cytology
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● Cellular; single and tightly packed clusters of oval to spindle cells aggregated around branched capillaries
● Often basement membrane material present
● Nuclei are uniform, oval, with finely granular chromatin and indistinct nucleoli
● No mitotic figures, no necrosis (Cancer 1999;87:190)

Virtual slides
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Hemangiopericytoma

Positive stains
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● CD99, vimentin, variable CD34 (Hum Pathol 1998;29:636)
● Reticulin surrounds individual cells
● If pericytic differentiation, with silver stain, spindle cells are outside the endothelial basement membrane

Negative stains
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● Factor VIII, CD31, trichrome, usually actin and desmin (except in sinonasal hemangiopericytoma)

Electron microscopy description
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● Has fibroblastic or undifferentiated spindle cell features
● No true pericytic differentiation (pericytic features are cytoplasmic filaments and processes, pinocytotic vesicles, basal lamina, poorly formed intercellular junctions)

Molecular description
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● 12q13-15 alterations in some cases

Differential diagnosis
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● Deep fibrous histiocytoma: storiform pattern, fibrohistiocytic lesion
● Endometrial stromal sarcoma: CD10+, ER+ (Mod Pathol 2005;18:40)
Infantile fibrosarcoma
Mesenchymal chondrosarcoma: islands of mature cartilage; malignant chondrocytes present
MPNST
● Myopericytoma: predominant growth pattern is concentric perivascular arrangement of plump spindle cells (J Clin Pathol 2006;59:67)
Solitary fibrous tumor: more prominent collagen, less prominent vessels
Synovial sarcoma-monophasic:: similar vascular pattern, characteristic translocation
● Thymoma: has epithelial foci

Additional references
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eMedicine, Orphanet, J Pediatr Hematol Oncol 2011;33:356 (childhood tumors)


Infantile / congenital hemangiopericytoma
General
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Micro description
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● Immature cytology, frequent mitotic figures, necrosis, possibly neoplastic endothelial cells

Micro images
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Various images


Lipomatous hemangiopericytoma

General
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● Variant with mature adipose tissue, myxoid and sclerotic areas
● Also called adipocytic variant of solitary fibrous tumor (Hum Pathol 2000;31:1108)
● First described in 1995 (Am J Surg Pathol 1995;19:748)
● May have malignant histologic features (Am J Surg Pathol 2011;35:1177)

Epidemiology
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● Uncommon
● 2/3 males, usually thigh, lower extremity and retroperitoneum
● Only rarely recurs, does not metastasize

Case reports
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● 26 year old man with paratesticular mass (Can Urol Assoc J 2012;6:E131)
● 36 year old woman with tumor of skull base and parapharyngeal space (Otol Neurotol 2006;27:560)
● 39 year old man with mediastinal tumor (J Postgrad Med 2006;52:71)
● 41 year old woman with thigh tumor (Arch Pathol Lab Med 1999;123:941)
● 56 year old man with retroperitoneal mass (Case of the Week # 16)
● 56 year old woman with epigastric pain (World J Gastroenterol 2011;17:4835)

Gross description
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● Solid, tan-yellow

Gross images
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Thigh tumor

Micro description
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● Well circumscribed, patternless cellular areas, prominent hemangiopericytoma-like vessels, mature adipose tissue, variable collagen

Micro images
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Thigh tumor
Mediastinal tumor
Paratesticular
Stomach

Case of the Week #16:
Retroperitoneal mass

Cytology
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● May resemble myxoid liposarcoma (Diagn Cytopathol 2003;29:287)

Positive stains
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● Vimentin, CD99, CD34 (75%), bcl2 (60%)

Negative stains
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● CD31, desmin, keratin, actins, S100, GFAP MDM2 and CDK4

Electron microscopy description
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● Features of pericytes, no lipoblasts

Differential diagnosis
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● Various lipomas
● Liposarcoma (Am J Surg Pathol 1999;23:1201)

End of Soft Tissue Tumors > Fibroblastic / myofibroblastic tumors > Hemangiopericytoma


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