Stanford School of Medicine
Surgical Pathology Criteria
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Adult Fibrosarcoma

Definition

  • Malignant neoplasm composed of uniform, cytologically malignant spindled fibroblasts or myofibroblasts occurring over age 10

Diagnostic Criteria

  • A diagnosis of exclusion after other spindle cell sarcomas have been excluded
    • As currently defined, it is a rare tumor
  • Over age 10 years
  • Uniform cytologically atypical spindle cells
    • Elongate nuclei
    • Hyperchromatic, granular chromatin
    • Nucleoli may be multiple and prominent
    • Mitotic figures usually frequent and abnormal
    • Scant cytoplasm
  • Broad cellular fascicles
    • Frequent herringbone pattern (intersection at acute angles)
    • May be long sweeping fascicles
  • Stroma scant to collagenous
    • Diffuse collagen abundant only in low grade tumors
    • Rarely keloid like collagen bundles
    • Stroma may be focally myxoid
    • Infrequent cartilaginous or osseous metaplasia
    • Areas indistinguishable from fibromatosis may be present
  • Immunohistochemistry must not show evidence of specific differentiation
    • Keratin, desmin, CD34, S100 negative
    • Actin variable
  • See separate entities:

    Richard L Kempson MD
    Robert V Rouse MD
    Department of Pathology
    Stanford University School of Medicine
    Stanford CA 94305-5342

    Original posting: October 15, 2007
    Last Update: January 26, 2008

 

Supplemental studies

Immunohistology

Fibrosarcoma by definition must not show evidence of specific differentiation

Actin variable
Desmin negative
CD34 negative
S100 negative
Keratin negative

Differential diagnosis

Nodular Fasciitis Adult Fibrosarcoma
Rare over 5 cm Usually over 4 cm
Undulating pattern Herringbone pattern
Atypical mitotic figures rare Atypical mitotic figures common
Fine, pale, even chromatin Coarse, granular, irregular chromatin
Torn appearance of stroma Lacks torn appearance

 

Extra-abdominal Desmoid Fibromatosis Adult 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 (except in low grade fibrosarcoma)
Atypical mitotic figures rare Atypical mitotic figures common
Cells separated by collagen Cells usually touch each other
Distinction may not always be clear and may be indistinguishable in low grade areas

 

Adult Fibrosarcoma Monophasic Synovial Sarcoma
Usually extensive herringbone pattern Herringbone pattern usually only focal
Keratin, EMA negative Keratin, EMA often positive
No ropy collagen Ropy collagen frequent
Calcification rare Calcification may be present
No hemangiopericytomatous vessels Hemangiopericytomatous vessels frequent
Thin elongate nuclei Plump nuclei
Chromatin not stippled Stippled chromatin
No SYT-SSX gene fusion SYT-SST gene fusion present
TLE1 0% (0/3) TLE1 97%

 

Malignant Fibrous Histiocytoma Adult Fibrosarcoma
Pleomorphic Uniform
May show histiocytic differentiation No histiocytic differentiation
Distinction is definitional as pleomorphism is not permitted in fibrosarcoma

 

Leiomyosarcoma of Deep Soft Tissue or Retroperitoneum Adult or Infantile Fibrosarcoma
Frequently desmin positive Desmin negative
Frequently pleomorphic Uniform
May occur in retroperitoneum or pelvis Rare in retroperitoneum and pelvis
Lacks t(12;15) t(12;15) usually present in infantile fibrosarcoma
Distinction may be arbitrary in some cases but desmin positive neoplastic cells exclude fibrosarcoma

 

Dermatofibrosarcoma Protuberans Adult or Infantile Fibrosarcoma
CD34 positive CD34 negative
Storiform pattern Fascicular, herringbone pattern
Involves dermis and subcutaneous tissue Virtually always in deep soft tissue
DFSP may dedifferentiate with a fibrosarcoma pattern
If fibrosarcoma occurs in the dermis or subcutaneous tissue, it is usually dedifferentiated DFSP

 

GI Stromal Tumor Adult Fibrosarcoma
Intra-abdominal Rare in abdomen
May be pleomorphic Uniform
CD34 60-70% positive CD34 negative
CD117 95% positive CD117 negative

 

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

  • Over age 10 by definition
    • Most 40-55 years
  • Virtually always in deep soft tissues
    • May occur superficially as dedifferentiated DFSP
    • Most common in legs and trunk
    • Very rare in retroperitoneum and mediastinum
    • May occur in retroperitoneum as component of dedifferentiated liposarcoma
  • Recurrence and distant metastatic rate about 50%
  • Lymph node metastases rare

Grading/Staging/Report

  • Grading is useful for predicting behavior in fibrosarcoma
    • Grade I fibrosarcomas recur but have a very low metastatic rate
    • Grade II and III fibrosarcomas have a metastatic rate of about 50%
  • Grading scheme from Fascicle
    • Grade I
      • Nuclei slightly larger, slightly more abnormal than in fibromatosis
      • Stroma abundant, collagenous
      • Necrosis and hemorrhage uncommon
    • Grade II
      • Features intermediate between Grades I and III
      • Necrosis and hemorrhage common
    • Grade III
      • Nuclei with dense granular chromatin
      • Densely packed cells with little collagenous stroma
      • Necrosis and hemorrhage common
      • Frequent mitotic figures
    • If features are discrepant, the nuclear findings take precedence
  • French Federation of Cancer Centers System grading scheme for adult sarcomas
    • Tumor differentiation score = 2 for fibrosarcoma
    • Mitotic index
      • Score 1 0-9 mitoses per 10 hpf (0.1744 sq mm)
      • Score 2 10-19 mitoses per 10 hpf
      • Score 3 >19 mitoses per 10 hpf
    • Tumor cell necrosis
      • Score 0 No necrosis on any slide (one slide per 2 cm tumor diameter)
      • Score 1 <50% of tumor is necrotic on slides examined
      • Score 2 >50% of tumor is necrotic on slides examined
    • Final Grade (add the three scores above)
      • Grade 1 Sum of scores = 2 or 3
      • Grade 2 Sum of scores = 4 or 5
      • Grade 3 Sum of scores = 6 or more

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
    • Grade
    • 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

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
  • Scott SM, Reiman HM, Pritchard DJ, Ilstrup DM. Soft tissue fibrosarcoma. A clinicopathologic study of 132 cases. Cancer. 1989 Aug 15;64(4):925-31.
 
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