Malignant peripheral nerve sheath tumor (MPNST) and malignant triton tumor
(MPNST with rhabdomyoblastic differentiation), potential candidates on morphologic grounds alone, arise often from a large peripheral nerve in patients with known neurofibromatosis.
The first patients in the registry include 17 survivors of lymphoma, 8 survivors of sarcoma, 5 survivors of Wilm's tumor, 4 survivors of neuroblastoma, and 1 survivor each of hepatoblastoma, ovarian germ cell tumor, yolk sac carcinoma, and Triton tumor
Malignant triton tumor
of the nose and paranasal sinuses:A case study.
One tumor (case 1) was a malignant Triton tumor, that is, an MPNST with rhabdomyomatous differentiation.
Smooth muscle actin expression in case 1, a malignant Triton tumor, was seen predominantly in the rhabdomyoblasts.
A true triton tumor
is a malignant peripheral nerve sheath tumor with rhabdomyoblastic differentiation, and it is more common than a "benign triton tumor
Pathologic Diagnosis: Collision Tumor (Malignant Triton Tumor and Ependymoma)
Malignant triton tumor is a histologic variant of MPNST showing rhabdomyoblastic differentiation.
The immunostains are helpful in differentiating these tumors from malignant triton tumor An occasional "ancient" schwannoma may show nuclear pleomorphism but lacks mitosis and necrosis.
In summary, to our knowledge this is the first reported case of a collision tumor (malignant triton tumor and ependymoma) at this anatomic location.
1] The third case is a malignant triton tumor
that contained malignant glands and rhabdomyoblasts.