Definition: Plexiform fibrohistiocytic tumor is a low-grade malignant myofibroblastic tumor of children, adolescents and young adults.
Synopsis
most occur in the upper extremity (63.1-69%)
female predominance
ill-defined, infiltrative mass of the subcutaneous adipose tissue
possible extension in the dermis and/or skeletal muscle
multinodular or plexiform proliferation of mononuclear histiocyte-like cells
spindle fibroblast-like cells
multinucleated osteoclast-like giant cells
three distinct growth patterns :
- fibrohistiocytic (36%)
- fibroblastic (32%)
- mixed (32%)
cellular atypia and pleomorphism rare or absent; usually less than 3 mitoses/10 HPF
rare vascular involvement reported
hyaline collagen
rare myxoid changes
+/- mucin deposits
frequent foci of microhemorrhage
possible osseous metaplasia
occasional chronic inflammatory infiltrate in or around the nodules
Immunohistochemistry
spindle cells usually express SMA and histiocyte-like cells occasionally
histiocytic and osteoclast-like cells express CD68, spindle cells oly rarely
unusual positivity for alpha-1-antitrypsin or alpha-1-antichymotrypsin
occasional faint and focal CD34 and CD57 staining
S100, desmin, cytokeratin, factor-VIII-related protein, lyzosyme, factor XIIIa negative
Variants
myxoid plexiform fibrohistiocytic tumour (12428852)
metastatic forms (9130995)
devoid of osteoclast-like giant cells (12357200)
Cytogenetics
t(8;?) (p22;?) (2164878)
t(4;15)(q21;q15) (9973942)
Differential diagnosis
granulomatous inflammation
- granuloma annulare
fusiform cell soft tissue tumors
- dermatofibrosarcoma protuberans
- fibrous hamartoma of infancy
- plexiform neurofibroma
- soft tissue giant cell tumor
- infantile myofibromatosis
- cellular neurothekeoma
- well-differentiated fibrosarcoma
- congenital dermatofibroma protuberans
- nodular fasciitis
- plexiform neurofibroma
Prognosis
frequent recurrence (12.5-40%) within 1-2 years after original diagnosis
extremely rare lymph node metastases
extremely rare pulmonary metastases
See also
myofibroblastic tumors
fusiform cell tumors
References
Neurothekeoma and Plexiform Fibrohistiocytic Tumor: Mere Histologic Resemblance or Histogenetic Relationship? Jaffer S, Ambrosini-Spaltro A, Mancini AM, Eusebi V, Rosai J. Am J Surg Pathol. 2009 Apr 1. PMID: 19342943
Leclerc S, Hamel-Teillac D, Oger P, Brousse N, Fraitag S. Plexiform fibrohistiocytic tumor: three unusual cases occurring in infancy. J Cutan Pathol. 2005 Sep;32(8):572-6. PMID: 16115057
Remstein ED, Arndt CA, Nascimento AG. Plexiform fibrohistiocytic tumor: clinicopathologic analysis of 22 cases. Am J Surg Pathol. 1999 Jun;23(6):662-70. PMID: 10366148
Salomao DR, Nascimento AG. Plexiform fibrohistiocytic tumor with systemic metastases: a case report. Am J Surg Pathol. 1997 Apr;21(4):469-76. PMID: 9130995
Zelger B, Weinlich G, Steiner H, Zelger BG, Egarter-Vigl E. Dermal and subcutaneous variants of plexiform fibrohistiocytic tumor. Am J Surg Pathol. 1997 Feb;21(2):235-41. PMID: 9042292
Thomazy V, Nagy A, Gal I, Nemes Z. Plexiform fibrohistiocytic tumour with novel phenotypic features. Histopathology. 1994 Aug;25(2):165-9. PMID: 7982679
Enzinger FM, Zhang RY. Plexiform fibrohistiocytic tumor presenting in children and young adults. An analysis of 65 cases. Am J Surg Pathol. 1988 Nov;12(11):818-26. PMID: 2847569
Salamanca J, Rodriguez-Peralto JL, Garcia de la Torre JP, Lopez-Rios F. Plexiform fibrohistiocytic tumor without multinucleated giant cells: a case report. Am J Dermatopathol. 2002 Oct;24(5):399-401. PMID: 12357200