Breast malignant, males, children
Sarcoma
Malignant Peripheral Nerve Sheath Tumor (MPNST)

Authors: Emily S. Reisenbichler, M.D. (see Authors page)

Revised: 28 November 2016, last major update November 2016

Copyright: (c) 2002-2016, PathologyOutlines.com, Inc.

PubMed Search: Malignant Peripheral Nerve Sheath Tumor [title] breast
Cite this page: Malignant Peripheral Nerve Sheath Tumor (MPNST). PathologyOutlines.com website. http://www.pathologyoutlines.com/topic/breastmalignantmpnst.html. Accessed December 8th, 2016.
Definition / General
  • Spindle cell sarcoma showing histologic, immunohistochemical or ultrastructural features of Schwann cell differentiation
  • Not a part of WHO classification in the breast
Essential Features
  • Accounts for less than 10% of all soft tissue sarcomas; exceedingly rare in breast
  • May occur sporadically or arise from a preexisting nerve sheath tumor, usually a neurofibroma in a neurofibromatosis 1 (NF1) patient
  • Shows varied morphology ranging from spindled (fibrosarcoma-like) to epithelioid cytology
  • Rare / patchy staining makes this a difficult tumor to diagnose by immunohistochemistry, particularly in sporadic cases
Etiology
Clinical Features
  • Typically presents as large, palpable mass (mean size > 5 cm)
Diagnosis
  • Low grade MPNST: resembles neurofibroma but with increased cellularity and scattered mitotic activity
  • High grade MPNST: resembles a high grade spindle cell sarcoma
  • Epithelioid type
  • Malignant Triton tumor: contains areas of rhabdomyoblastic differentiation
Prognostic Factors
  • Association with NF1 portends a worse prognosis
Case Reports
Treatment
  • Like most soft tissue tumors, wide excision with negative margins is the mainstay of treatment
  • Radiation may reduce recurrence but data is limited due to its rarity
Gross Description
  • Large tumor with solid cut surface and generally circumscribed borders
Micro Description
  • Typically spindle cell cytology but can be epithelioid
  • Wavy, buckled nuclei
  • Fascicles of alternating hyper- and hypocellular areas
  • Collagenous stroma
  • Perivascular accentuation, often with areas of necrosis
  • Can see areas of heterologous differentiation (osteo-, chondro- or rhabdomyosarcomatous differentiation)
  • Rare cases may show glandular differentiation
Micro Images

Images hosted on PathOut server:

Contributed by Dr. Emily S. Reisenbichler (left: 10x; right: 20x)

Contributed by Dr. Mark R. Wick



Images hosted on other servers:

H&E, S100

H&E

Positive Stains
  • S100: typically focal / patchy; low grade MPNST arising in a neurofibroma and epithelioid MPNST may be diffusely positive
  • SOX10, GFAP, CD34
  • Desmin: may highlight areas of rhabdomyoblastic differentiation
Negative Stains
  • Keratins: except in rare cases with glandular differentiation
  • INI1 loss in a portion of epithelioid variant
Molecular / Cytogenetics Description
  • Complex karyotypes but no known consistent molecular alterations
Differential Diagnosis
  • Dedifferentiated liposarcoma: both liposarcoma and MPNST may show MDM2 overexpression by immunohistochemical staining but dedifferentiated liposarcoma should show genuine MDM2 amplification by FISH; also CDK4 positive
  • Leiomyosarcoma: expression of smooth muscle markers (SMA, desmin, h-Caldesmon)
  • Neurofibroma: less cellular than MPNST and lacking significant nuclear atypia or mitotic activity (in an NF1 patient, virtually any mitotic activity is diagnostic of MPNST)
  • Rhabdomyosarcoma: desmin and muscle specific actin positive with nuclear MyoD1 and myogenin staining; MPNST with rhabdomyoblastic differentiation is usually a focal finding and typical MPNST morphology predominates
  • Spindle cell melanoma: diffuse S100 and SOX10 staining seen in melanoma is unusual in MPNST
  • Synovial sarcoma: monophasic type resembles MPNST morphologically but often shows patchy / focal EMA and keratin staining; biphasic type resembles a glandular MPNST and will show strong keratin staining of the glandular component; both MPNST and synovial sarcoma may show focal S100 or SOX10 staining but synovial sarcoma is characterized by a t(X;18)(p11;q11) translocation
  • Undifferentiated spindle cell sarcoma: by definition is a diagnosis of exclusion showing no specific line of differentiation