Soft tissue

Pericytic (perivascular)

Myopericytoma / myofibroma



Minor changes: 14 July 2021

Copyright: 2002-2021, PathologyOutlines.com, Inc.

PubMed Search: Myopericytoma[TI] OR myofibroma[TI] OR myofibromatosis[TI] soft tissue[TIAB] pathology

Borislav A. Alexiev, M.D.
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Cite this page: Alexiev BA. Myopericytoma / myofibroma. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/softtissuemyopericytoma.html. Accessed October 15th, 2021.
Definition / general
  • Myopericytoma is a distinctive perivascular myoid neoplasm that forms a morphological spectrum with myofibroma
Essential features
  • Myopericytoma: bland, myoid spindled cells growing in a concentric pattern around numerous small blood vessels
  • Myofibroma: biphasic growth pattern, with primitive cellular zones often showing mitotic activity, necrosis and calcification, surrounded by hyalinized nodules of myoid spindled cells
  • PDGFRB mutations in myopericytoma and myofibroma
  • SRF-RELA gene fusions in cellular myofibroma / myopericytoma
Terminology
  • Not recommended: infantile hemangiopericytoma
ICD coding
  • ICD-O: 8824/0 - myopericytoma
  • ICD-11: 2E84.Y & XH0953 - benign fibrogenic or myofibrogenic tumor of other specified sites & myofibroma
Epidemiology
  • Myopericytoma may occur at any age; most cases are seen in adults
  • Myofibroma may be present at birth, appear in the first 2 years of life or arise in adults, with male predominance (Am J Surg Pathol 2006;30:104)
Sites
Pathophysiology
Etiology
Clinical features
Diagnosis
  • Tissue sampling is the gold standard for a definitive diagnosis
Radiology description
  • At magnetic resonance imaging, tumors are most commonly superficial, may be well defined (myopericytoma) or ill defined (myopericytomatosis) and demonstrate highly vascularized, avidly enhancing soft tissue, often with areas of internal hemorrhage (Radiol Case Rep 2017;13:275)
Radiology images

Contributed by Borislav A. Alexiev, M.D.
Myopericytoma, MRI

Myopericytoma, MRI

Prognostic factors
  • Most myopericytomas and myofibromas do not recur
  • Small subset of myofibromas / myopericytomas shows atypical features (diffuse hypercellularity, infiltrative growth pattern and increased mitotic figures) that do not adversely affect outcome (Am J Surg Pathol 2014;38:1649)
  • Malignant myopericytomas are associated with aggressive clinical behavior (Histopathology 2002;41:450)
  • Multicentric myofibroma (referred to as infantile myofibromatosis) is a life threatening disease (JAMA Dermatol 2019;155:946)
Case reports
Treatment
Gross description
  • In superficial locations, myopericytoma tends to be well circumscribed, with nodules measuring < 2 cm
  • Larger neoplasms may be seen in deep soft tissue (Am J Surg Pathol 2006;30:104)
  • Tan-white, firm cut surface
Gross images

Contributed by Borislav A. Alexiev, M.D.
Soft tissue mass

Soft tissue mass

Frozen section description
  • Concentric, perivascular growth of plump spindled, myoid cells
Microscopic (histologic) description
  • Myopericytoma
    • Well circumscribed, nodular or lobular lesions
    • Bland, oval to spindle shaped, myoid cells
    • Characteristic multilayered, concentric growth around numerous small vessels
    • Variable cellularity, ranging from cellular and solid appearing to hypocellular and collagenous / myxoid (Am J Surg Pathol 2006;30:104)
    • Numerous blood vessels and variable in size; branching, hemangiopericytoma-like blood vessels may be present
    • In some cases, a more prominent fascicular arrangement of neoplastic cells is present
    • Some myopericytomas may show degenerative changes (symplastic nuclear atypia, stromal hyalinization and cystic change)
    • Myopericytomatosis is a rare, diffuse benign variant of myopericytoma that typically involves superficial soft tissue in adults with innumerable microscopic myopericytomatous nodules (Am J Surg Pathol 2017;41:1034)
  • Myofibroma
    • Well circumscribed, nodular neoplasms characterized by a distinctive biphasic growth pattern (Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2000;89:57)
    • Center of the lesion is composed of immature appearing, plump, spindled tumor cells associated with hemangiopericytoma-like branching blood vessels
    • Periphery of the lesion consists of nodules and fascicles of variably hyalinized, myoid appearing cells
    • Pattern of zonation may be more haphazard or even reversed (Histopathology 1993;22:335)
    • Mitotic figures are variable in number
    • Cellular zones may undergo necrosis and calcification
    • In infants, myofibromas may be composed almost entirely of primitive, cellular zones; such cases were historically labeled infantile hemangiopericytoma (Am J Surg Pathol 1994;18:922)
    • Morphological features of the cellular zones of myofibroma share some features with myopericytoma, suggesting that these are related entities
    • Myofibromatosis is defined by the presence of multiple myofibromas
  • Myofibroma / myopericytoma with cellular / atypical features
  • Malignant myopericytoma
    • Highly mitotic myoid appearing ovoid to spindle cells
    • Marked nuclear atypia / pleomorphism
    • Tumor necrosis
    • At least focally striking perivascular orientation resembling that seen in benign myopericytoma (Histopathology 2002;41:450)
Microscopic (histologic) images

Contributed by Borislav A. Alexiev, M.D., Hillary Rose Elwood, M.D. and Mark R. Wick, M.D.
Well circumscribed lesion

Well circumscribed lesion

Multilayered, concentric growth

Multilayered, concentric growth

Hemangiopericytoma-like vessels

Hemangiopericytoma-like
vessels

Perivascular proliferation

Perivascular proliferation

Smooth muscle actin

Smooth muscle actin

h-caldesmon

h-caldesmon


Well circumscribed nodule

Well circumscribed nodule

Biphasic proliferation Biphasic proliferation

Biphasic proliferation

Biphasic morphology

Biphasic morphology

Increased cellularity

Increased cellularity

Stromal hyalinization

Stromal hyalinization

Molecular / cytogenetics description
Sample pathology report
  • Right foot mass, excision:
    • Myopericytoma (see comment)
    • Comment: Histologically, the neoplasm has a well circumscribed margin and is composed of numerous thick walled vessels, with a concentric, perivascular arrangement of ovoid, plump spindled to round myoid tumor cells with an abundant cytoplasm and spindled or round nuclei with evenly distributed chromatin. Areas with hemangiopericytoma type growth pattern, characterized by dilated branching thin walled vessels surrounded by evenly distributed spindled neoplastic cells are also noted. Degenerative stromal changes, such as stromal fibrosis, hyalinization and myxoid change, are seen. Mitotic figures, tumor necrosis and vascular invasion are not identified. Immunohistochemically, the tumor stains positively for SMA and h-caldesmon, while all of the following are negative: S100, desmin, keratin AE1 / AE3 and HMB45. The morphological features and immunohistochemical profile support the above diagnosis.
    • Myopericytoma is a benign tumor that rarely recurs following marginal or even intralesional excision. Simple surgical excision is adequate treatment.
Differential diagnosis
Board review style question #1
Which of the following is true about myofibroma / myofibromatosis?

  1. Multicentric infantile myofibromatosis is more common in males
  2. Multiple lesions with visceral involvement can affect virtually any internal organ and are associated with a poor prognosis
  3. Solitary infantile myofibromatosis is more common in females
  4. Tumor is positive for keratin
  5. Tumor is positive for NOTCH gene fusions
Board review style answer #1
B. Multiple lesions with visceral involvement can affect virtually any internal organ and are associated with a poor prognosis

Comment Here

Reference: Myopericytoma / myofibroma
Board review style question #2

A 38 year old man presented with a left thigh mass. Hematoxylin eosin stains demonstrate a well circumscribed tumor in the dermis and subcutaneous fat composed of bland, oval to spindle shaped cells with multilayered concentric growth around numerous small thick walled blood vessels. Neither necrosis nor mitotic activity is identified. Immunohistochemical stains for SMA and h-caldesmon are positive in tumor cells, while all of the following are negative: keratin AE1 / AE3, CD34, desmin, HMB45, S100 and STAT6.

Which of the following is most likely the correct diagnosis?

  1. Leiomyoma
  2. Myofibroblastoma
  3. Myopericytoma
  4. PEComa
  5. Solitary fibrous tumor
Board review style answer #2
C. Myopericytoma

Comment Here

Reference: Myopericytoma / myofibroma
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