plexiform malignant peripheral nerve sheath tumor
Although no metastase has been described, the histologic similarity of plexiform MPNST to other childhood MPNST, its relatively high propensity for local recurrences, and its potential to behave in a locally aggressive manner indicate that it is best regarded as low-grade malignant.
Overall, the behavior of plexiform MPNST is better than other MPNST in children, probably because of its relatively small size, peripheral and superficial location in most instances, absence of necrosis or vascular invasion, occurrence in young patients, and infrequent association with von Recklinghausen’s disease rather than a function of its prominent plexiform architecture.
Synopsis
lower extremities, upper extremities, orbital region (one case)
from 1.5 to 8 cm in size (median, 3 cm)
+/- congenital
+/- von Recklinghausen’s disease
predominantly superficial location within the dermis and subcutis
occasional extension into deeper soft tissues
infiltrative or sharply demarcated margins
resembled entangled or intertwined hypercellular nerve trunks, resulting in a plexiform appearance at low magnification
nuclei oval to serpentine with a vesicular chromatin pattern and small basophilic nucleoli
mitoses seen (average: 1 to 18/10 high-power fields (hpf) - median, 4/10 hpf)
neither necrosis nor vascular invasion
Differential diagnosis
Features diagnostic of plexiform or cellular schwannoma, such as nuclear pleomorphism, Antoni B areas, thick-walled hyalinized blood vessels, and secondary degenerative features are lacking.
Other than a prominent plexiform architecture, the lesions were indistinguishable from MPNST occurring in other sites in infants and children.
Distinction of plexiform MPNST from cellular and plexiform schwannoma, plexiform neurofibroma, and hamartomatous lesions of childhood is important. Complete excision should be ensured to prevent local recurrences and potential metastases.
References
Plexiform malignant peripheral nerve sheath tumor of infancy and childhood. Meis-Kindblom JM, Enzinger FM. Am J Surg Pathol. 1994 May;18(5):479-85. PMID: #7513502#