title: Morphologic Overlap between Infantile Myofibromatosis and Infantile Fibrosarcoma: A Pitfall in Diagnosis.
abstract: Infantile myofibromatosis (IM) is a distinctive mesenchymal disorder with different clinical forms, including solitary, multicentric, and generalized with visceral involvement. A wide morphologic spectrum is encountered, with the extremes resembling congenital infantile fibrosarcoma (CIFS) and infantile hemangiopericytoma. We report a series of lesions with mixed features of CIFS and IM and compare them in order to further define their clinicopathologic features and the significance of the so-called composite fibromatosis. Seven lesions with unusual overlapping morphologic "composite" features of both IM and CIFS were selected from a series of 106 myofibroblastic lesions. Three cases classified as composite infantile myofibromatoses (COIM) were highly cellular tumors with a diffuse growth of primitive mesenchymal cells and focal features of IM combined with areas resembling infantile fibrosarcoma (IF). Four cases were classified as IF. Three of these exhibited a biphasic pattern with foci resembling IM, including whorls of primitive and spindle cells and perivascular and intravascular projections of myofibroblastic nodules, and the 4th had a close histologic resemblance to a primitive, immature IM. With reverse transcriptase polymerase chain reaction, the ETV6-NTRK3 transcript was absent in 3 COIM and was detected in 3 CIFS; the other CIFS had typical cytogenetic aberrations. On the basis of currently available information, COIM represents a morphologic variant of IM that can mimic IF. Careful histologic evaluation to detect the typical features of IM is essential to avoid classification as IF. Molecular analysis for the ETV6-NTRK3 gene fusion is an important diagnostic tool in this group of lesions.
authors.affiliation: Dipartimento di Scienze Oncologiche e Chirurgiche Azienda Ospedaliera-Università di Padova, Padova, Italy.
authors.forename: Rita
authors.initials: R
authors.lastname: Alaggio
authors.forename: Donatella
authors.initials: D
authors.lastname: Barisani
authors.forename: Vito
authors.initials: V
authors.lastname: Ninfo
authors.forename: Angelo
authors.initials: A
authors.lastname: Rosolen
authors.forename: Cheryl M
authors.initials: CM
authors.lastname: Coffin
mesh_terms: D000199:Actins / Q000378:metabolism; D018952:Antigens, CD34 / Q000378:metabolism; D002881:Chromosomes, Human, Pair 12 / Q000737:chemistry; D002884:Chromosomes, Human, Pair 15 / Q000737:chemistry; D018076:DNA, Complementary / Q000096:biosynthesis; D003937:Diagnosis, Differential; D005260:Female; D005354:Fibrosarcoma / Q000737:chemistry / Q000151:congenital / Q000175:diagnosis* / Q000235:genetics / Q000473:pathology*; D006801:Humans; D007150:Immunohistochemistry; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D018224:Myofibromatosis / Q000151:congenital / Q000175:diagnosis* / Q000235:genetics / Q000473:pathology*; D015514:Oncogene Proteins, Fusion / Q000235:genetics; D012334:RNA, Neoplasm / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014178:Translocation, Genetic; D014746:Vimentin / Q000378:metabolism; D020812:Receptor, trkC; D000097764:ETS Translocation Variant 6 Protein
chemical_list: D000199:Actins; D018952:Antigens, CD34; D018076:DNA, Complementary; D015514:Oncogene Proteins, Fusion; D012334:RNA, Neoplasm; D014746:Vimentin; C484319:ETV6-NTRK3 fusion protein, human; D020812:Receptor, trkC; D000097764:ETS Translocation Variant 6 Protein