Definition
Malignant neoplasm composed of uniform, cytologically malignant spindled fibroblasts or myofibroblasts occurring under age 10
Alternate/Historical Names
Congenital fibrosarcoma
Desmoplastic fibrosarcoma of infancy
Juvenile fibrosarcoma
Medullary fibromatosis of infancy
Diagnostic Criteria
Under age 10 years
Uniform spindle cells
Elongate nuclei
Scant cytoplasm
May have round cell areas
Must have conventional areas also
Hyperchromatic, granular chromatin
Nucleoli may be multiple and prominent
Mitotic figures usually frequent and abnormal
Broad cellular fascicles
Frequent herringbone pattern (intersection of fascicles at acute angles)
May be long sweeping fascicles
Scant stroma
Stroma may be focally myxoid
Must have conventional areas also
May have dilated congested vessels
May have hemangiopericytic vessels
Frequently scattered chronic inflammatory cells
Immunohistochemistry must not show evidence of specific differentiation
Actin variable
Desmin, CD34, S100 negative
See separate entities:
Richard L Kempson MD
Original posting: October 15, 2007
Supplemental studies
Immunohistology
Fibrosarcoma by definition must not show evidence of specific differentiation
Actin (smooth muscle or muscle specific) may be seen in about 1/3 of cases
Other markers show only focal cell reactivity at most
Keratin, desmin, S100, CD34
Genetics
t(12;15) (p13;q26) present in most cases
Involves NTRK3 tyrosine kinase receptor
Same translocation has been identified in congenital mesoblastic nephroma
Cytogenetic confirmation required if patient >2 years of age
Differential diagnosis
Myofibroma Infantile Fibrosarcoma
Random spindle cell pattern
Fascicular pattern
Biphasic mature and immature areas
No biphasic pattern
Atypical mitotic figures rare
Atypical mitotic figures common
Infantile Fibromatosis Infantile Fibrosarcoma
Mild to moderate cellularity
Usually more cellular
Fine chromatin
Usually clumped chromatin
Rarely > 5 mitotic figures per HPF
Usually > 5 mitotic figures per HPF
Atypical mitotic figures rare
Atypical mitotic figures common
Variably collagenous stroma
Little collagen in stroma
No herringbone pattern
Frequent herringbone pattern
Hemorrhage and necrosis rare
Frequent hemorrhage and necrosis
Muscle fibers preserved
Muscle fibers destroyed
Lacks t(12;15)
t(12;15) in most cases
Distinction between grade I fibrosarcoma and desmoid fibromatosis may not always be clear
Infantile Fibrosarcoma Monophasic Synovial Sarcoma
May have extensive herringbone pattern
Herringbone pattern usually only focal
Keratin, EMA negative or at most focal
Keratin, EMA usually positive
No ropy collagen
Ropy collagen frequent
Calcification rare
Calcification common
Elongate nuclei
Plump nuclei
Chromatin not stippled
Stippled chromatin
t(12;15) usually present
SYT-SST gene fusion present
Both may have hemangiopericytomatous vessels
Embryonal Rhabdomyosarcoma
Infantile Fibrosarcoma
Desmin and myogenin positive
Desmin and myogenin negative
No areas of conventional fibrosarcoma
Areas of conventional fascicular pattern present
Infantile fibrosarcoma may have round cell areas reminiscent of rhabdomyosarcoma
Malignant Peripheral Nerve Sheath Tumor
Adult or Infantile Fibrosarcoma
May be S100 positive (50%)
S100 negative
May be pleomorphic
Uniform
May arise from nerve or neurofibroma
No relation to nerve or neurofibroma
May arise in von Recklinghausen disease
Not related to von Recklinghausen disease
Lacks t(12;15)
t(12;15) usually present in infantile fibrosarcoma
Cellular Fibroma of Tendon Sheath Adult or Infantile Fibrosarcoma
Common in hands
Rare in hands in adults but may involve hands in infantile version
Rare >2 cm
Frequently >4 cm
Cytologically bland
Cytologically atypical
No atypical mitotic figures
Atypical mitotic figures may be seen
Smooth muscle actin strongly positive
Actin variable
Lacks t(12;15)
t(12;15) present in most infantile cases
Clinical
Under age 10 by definition
Most <2 years
May be congenital
Few between 2 and 10 years
May involve deep soft tissues or subcutaneous tissues
Most common in extremities
Very rare in retroperitoneum and mediastinum
Behavior under age 5 years
Recurrence rate about 25%
Metastatic rate <10%
Report
Grading does not predict outcome
Use TNM Staging
The surgical pathology report should contain or address the following:
Location
Type of resection or biopsy
Histologic diagnosis
Managerial category III (Local recurrence common; Metastasis occurs)
Extent of tumor cell necrosis
Stage
Size
Depth (dermis, subcutis, below fascia, body cavity)
Margins
Involved
Not involved
If under 2 cm give all such distances and sites
If over 2 cm give minimum distance and site
Results of supplementary studies if performed
Relationship to other specimens from the same patient
Lists
Predominantly fibrous soft tissue sarcomas
Predominantly Pediatric Fibrous Lesions
Lesions that may demonstrate a prominent hemangiopericytoma-like vascular pattern
Bibliography
Kempson RL, Fletcher CDM, Evans HL, Henrickson MR, Sibley RS. Tumors of the Soft Tissues, Atlas of Tumor Pathology, AFIP Third Series, Fascicle 30, 2001
Fletcher CDM, Unni KK, Mertens F. Pathology and Genetics of Tumours of Soft Tissue and Bone, World Health Organization Classification of Tumours 2002
Weiss SW, Goldblum JR. Enzinger and Weiss's Soft Tissue Tumors, 4th edition, 2001
Coffin CM, Jaszcz W, O'Shea PA, Dehner LP. So-called congenital-infantile fibrosarcoma: does it exist and what is it? Pediatr Pathol. 1994 Jan-Feb;14(1):133-50.
Kodet R, Stejskal J, Pilat D, Kocourkova M, Smelhaus V, Eckschlager T. Congenital-infantile fibrosarcoma: a clinicopathological study of five patients entered on the Prague children's tumor registry. Pathol Res Pract. 1996 Aug;192(8):845-53; discussion 854-5.
Coffin CM, Dehner LP. Fibroblastic-myofibroblastic tumors in children and adolescents: a clinicopathologic study of 108 examples in 103 patients. Pediatr Pathol. 1991 Jul-Aug;11(4):569-88.
Bourgeois JM, Knezevich SR, Mathers JA, Sorensen PH. Molecular detection of the ETV6-NTRK3 gene fusion differentiates congenital fibrosarcoma from other childhood spindle cell tumors. Am J Surg Pathol. 2000 Jul;24(7):937-46.
Sheng WQ, Hisaoka M, Okamoto S, Tanaka A, Meis-Kindblom JM, Kindblom LG, Ishida T, Nojima T, Hashimoto H. Congenital-infantile fibrosarcoma. A clinicopathologic study of 10 cases and molecular detection of the ETV6-NTRK3 fusion transcripts using paraffin-embedded tissues. Am J Clin Pathol. 2001 Mar;115(3):348-55.
