Soft tissue
Fibroblastic / myofibroblastic tumors
Fibrosarcoma of soft tissue - infantile

Author: Komal Arora, M.D.

Revised: 30 January 2018, last major update July 2012

Copyright: (c) 2002-2018,, Inc.

PubMed Search: Fibrosarcoma [title] infantile

Cite this page: Arora, K. Fibrosarcoma of soft tissue - infantile. website. Accessed July 22nd, 2018.
Definition / general
  • Resembles adult fibrosarcoma morphologically, but better prognosis
  • Age cutoff between infantile and adult forms usually varies between 5 and 10 years
  • Usually presents before age 2 years in axial regions or extremities with vary rapid growth
  • Related to congenital mesoblastic nephroma, which has same translocation
Clinical features
  • 40 - 50% recur, but only rarely metastasizes
  • Survival is 90%+
Case reports
Gross description
  • May exceed 30 cm (grotesquely large compared to size of child) with tense erythematous and ulcerated overlying skin
  • Firm to soft cut surface is fleshy, gray-tan with myxoid change, cystic degeneration, hemorrhage and necrosis
Gross images

Images hosted on PathOut servers:

Fleshy white mass similar
to adult fibrosarcoma

Microscopic (histologic) description
  • Poorly circumscribed, lobulated mass of small to large spindled cells in fascicles or herringbone pattern with high cellularity, nuclear atypia and pleomorphism
  • Increased mitotic figures, hemorrhage and necrosis
  • Resembles adult fibrosarcoma
  • May have prominent hemangiopericytoma-like areas, dystrophic calcification, extramedullary hematopoiesis
  • Infiltrates adjacent soft tissue with irregular margins
Microscopic (histologic) images

Images hosted on PathOut servers:

Biphasic pattern with fibroblastic and cellular myxoid areas

High power of myxoid area

Infiltration of fat

Infiltration of muscle

Spindle cells

Plump cells have granular chromatin

Less cellular tumor which overlaps with infantile fibromatosis, although it almost never metastasizes

Images hosted on other servers:

Leg tumor

Images hosted on Nature servers:

Areas of variable cellularity

Tumor with features of infantile fibrosarcoma and congenital mesoblastic nephroma

Positive stains
Electron microscopy description
  • Fibroblastic and myofibroblastic features
Molecular / cytogenetics description
Molecular / cytogenetics images

Images hosted on Nature servers:

Ideogram of fusion transcript and FISH

Differential diagnosis
Additional references