Synopsis
infants or neonates (50%)
localization: trunk, extremities, and head and neck
nonencapsulated tumors
multinodular appearance
focal infiltrative growth
white fleshy cut surface
tumor diameter ranging from 2 to 15 cm
diffuse growth
primitive spindle cells or polygonal cells or round cells
myxoid background
vaguely nodular pattern
peripheral collagenized stroma
higher cellularity at the periphery
delicate vascular network in the background
Immunohistochemistry
diffuse reactivity for vimentin
no reactivity for smooth muscle actin, muscle specific actin, desmin, S-100 protein, or myogenin
Electron microscopy
poorly differentiated fibroblastic proliferation
Cytogenetics
Chr.Y rearrangements
Chr.9 rearrangements
Chr.3 rearrangements
Differential diagnosis
- embryonal rhabdomyosarcoma
- Ewing sarcoma/primitive neuroectodermal tumor
- congenital infantile fibrosarcoma
- primitive sarcomas
- undifferentiated sarcoma
Complications
possible recurrences
possible metastasis
References
Alaggio R, Ninfo V, Rosolen A, Coffin CM. Primitive myxoid mesenchymal tumor of infancy: a clinicopathologic report of 6 cases. Am J Surg Pathol. 2006 Mar;30(3):388-94. PMID: 16538060