Surgical Pathology Criteria

Malignant Peripheral Nerve Sheath Tumor


Alternate/Historical Names

Diagnostic Criteria



Differential Diagnosis


Conventional Schwannoma

Cellular Schwannoma


Biphasic, Antoni A and B areas

Uniform, Hypercellular (Majority Antoni A)


Variable chromatin

May show hyperchromasia

Pronounced hyperchromasia

Small nuclei

Small nuclei

Enlarged nuclei (3x normal)

Verocay bodies, hyalinized vessels, lipid laden histocytes, lymphoid infiltrates

Hyalinized vessels, lipid-laden histiocytes, lymphocytic infiltrates

All absent

Mitoses usually rare

Few mitoses (usu. <4/10 HPF)

Very mitotically active (usu. >10/10 HPF)

Strong, diffuse S100 immunoreactivity

Strong, diffuse S100 immunoreactivity

Weak, patchy S100 immunoreactivity

Rare necrosis

Poorly demarcated rare foci of necrosis without palisading

Geographic necrosis

Globoid, encapsulated

Globoid, encapsulated

Fusiform to globoid with infiltration

Rare divergent differentiation

Rare divergent differentiation

Occasional divergent differentiation (e.g., rhabdomyosarcoma in malignant triton tumor)


Schwannoma with Degenerative Atypia (Ancient Schwannoma)


Occasional bizarre, hyperchromatic cells, other cells cytologically benign

Uniform, cytologically malignant features

Normal cellularity

Marked cell crowding

Low mitotic activity

High mitotic activity

S100 positive

S100 variably positive


Neurofibroma with Degenerative Atypia (“ancient change”)


Localized cells with large, pleomorphic nuclei, cytoplasmic nuclear inclusions, smudgy chromatin, and inconspicuous nucleoli

Generalized atypia

No or very low mitotic activity

Increased mitotic activity

Low to moderate cellularity

Diffuse hypercellularity

S100 positive

S100 variably positive



Adult or Infantile Fibrosarcoma

May be S100 positive

S100 negative

More variable architecture

Uniform fascicular pattern

Generally more pleomorphic

Uniform, symmetric fusiform cells resembling fibroblasts

May arise from a nerve or neurofibroma

No relation to a nerve or neurofibroma

May arise in NF1

Not related to NF1

No consistent translocations

t(12;15) usually present in infantile fibrosarcoma



Synovial sarcoma

No consistent translocations

t(X;18;p11;q11) translocation

Prominent vessels uncommon

Hemangiopericytoma-like vessels

Hyperchromatic, wavy or buckled nuclei

Plump, stubby nuclei

Diffuse atypia

No more than mild pleomorphism

Glands rare but may be seen

Glands in biphasic synovial sarcoma

Keratin negative spindle cells

Spindled cells may be keratin positive

Calcifications uncommon

Calcifications common

TLE1 ipox 5% TLE1 ipox 97%
Both may or may not express S100



Wavy nuclei

Nuclei with blunt ends

Light, indistinct cytoplasm

Eosinophilic cytoplasm with juxtanuclear vacuoles

May be S-100 immunoreactive

S-100 negative, Smooth muscle markers positive

May be associated with nerve or neurofibroma

Not associated with nerve or neurofibroma



Desmoplastic Melanoma

May arise in existing nerve or neurofibroma

Fibrosing dermal lesion typically of head and neck

No association with atypical junctional melanocytes

Often associated junctional component of atypical melanocytes

No associated lymphoid infiltrate

Often lymphoid infiltrate

Variable, weak S-100 expression

Strong S-100 immunoreactivity

Light, indistinct cytoplasm

Amphophilic cytoplasm



Kurt Schaberg MD
Donald Born MD
Robert V Rouse MD
Department of Pathology
Stanford University School of Medicine
Stanford CA 94305-5342

Original posting : 9/2/15

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