Spindle cell lesions

Spindle cell lesions are seen frequent enough that one ought to have a solid approach to 'em.

General DDx

Spindle cells should make think:

• Nerve.
• Muscle.
  • Smooth.
  • Skeletal.
• Other.

Malignant fibrous histiocytoma

Work-up (MSH):

• CD34 - GIST, angiosarcoma, solitary fibrous tumour/hemangiopericytoma.
• S100 - neural marker, sensitive for malignant melanoma.
• Desmin - smooth muscle.
• MIB-1 - proliferation.
• CD99 - small round cell tumours, considered "slutty", i.e. non-specific, by Dr. Fletcher; useful if membranous stain pattern = Ewing sarcoma/PNET.
• Bcl-2.
• PGP 9.5.
• SMMS - smooth muscle.
• Caldesmon - muscle.
• PDGFR - GIST.
• DOG-1 - GIST (membranous, cytoplasmic), normal pancreas (islets), associated with BRCA1.

Others:

• Beta-catenin - a small subset of soft tissue lesions:
  • Desmoidtype fibromatosis (~70%), solitary fibrous tumour & endometrial stromal sarcoma (~40%), synovial sarcoma (~30%).

Notes:

• Bcl-2 -- loss associated with follicular lymphoma.

See also

• Bone.
• Dermatopathology.
• Hematopathology.
• Soft tissue lesions.
• Immunohistochemistry.