Dermatopathology

MPNST Triton Tumor

Malignant peripheral nerve sheath tumor (MPNST) with rhabdomyosarcomatous differentiation (Malignant Triton tumor).

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Slide 1: 80 year-old woman with a chest wall mass. The excision specimen consisted of a spindle cell lesion with a nodular configuration and variable cellularity.
Slide 2: An associated nerve (upper half of image) is identified in association with the lesion.
Slide 3: There is variable cellularity with less cellular areas (left) intermingled with highly cellular and more epithelioid looking areas (right of image).
Slide 4: Spindled areas with nuclear pleomorphism and conspicuous mitotic figures.
Slide 5: Cellular areas focally showing cells with prominent eosinophilic cytoplasm.
Slide 6: S100 was positive throughout the lesion, although only a fraction of the cells stained in any one field.
Slide 7: Focally, cells exhibit strong cytoplasmic staining with desmin.
Slide 8: Nuclear positivity for myogenin is evident in this field.
Slide 9: Nuclear positivity for MyoD1 is also focally identified.
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