Abstract
Fibroblastic and myofibroblastic tumors comprise a morphologically diverse and biologically variable group of neoplasms that affect a wide age range. Specific entities tend to occur most frequently in infants and young children. Recent years have witnessed a proliferation of information concerning the unique biology of these tumors. In this report, I will review recent findings that serve to further characterize this group of neoplasms. Included will be newer information on fibrous hamartoma of infancy, infantile myofibromatosis, lipofibromatosis, and infantile fibrosarcoma and tumors resembling it, including primitive myxoid mesenchymal tumor of infancy and new genetic entities. I will also discuss the differential diagnosis, which includes spindle cell rhabdomyosarcoma, dermatofibrosarcoma protuberans, and calcifying aponeurotic fibroma.
Highlights
Pediatric soft tissue tumor pathology comprises a wide variety of morphologic and genetic entities
Ki67 staining revealed that cellular proliferative index was high in the immature mesenchyme in some cases
Summary The previous decade has provided much biological information regarding an important tumor group that preferentially affects infants and young children. These lesions have the potential to lead to deformation, limited mobility, and death, but as our knowledge has expanded, so have available treatment options
Summary
Pediatric soft tissue tumor pathology comprises a wide variety of morphologic and genetic entities. Primitive myxoid mesenchymal tumor of infancy In 2006, Alaggio et al.[19] reported six cases of a previously unreported infantile tumor (three congenital) with infiltrative soft tissue masses of the trunk, extremities, and head and neck These were IFS-like but were negative for ETV6-NTRK3 fusion. In 2017, Flucke et al.[25] described a spindle cell sarcoma presenting as a mitotically active, large pelvic soft tissue mass in a four-month-old and strongly expressing S100 by IHC This lesion resembled IFS and, unlike malignant peripheral nerve sheath tumors, lacked SOX10 expression and retained H3K27me[3]. A recent study[26] suggests that some infantile rhabdomyosarcomas show a molecular profile differing from that of other rhabdomyosarcomas and resembling that of myofibroblastic tumors These lesions, the so-called SCRMSs, are most frequently encountered in the paratesticular soft tissue, followed by the head and neck[27]. Grant information The authors declare that no grants were involved in supporting this work
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