Angiomatoid Fibrous Histiocytoma (AFH)

Epidemiology and Etiology:

· Children and young adults (<30y usually)

Common sites:

· Subcutaneous usually

· Extremities

· Trunk

· Head and neck

Gross features:

·

Histologic features:

· Solid, lobulated sheets

· Nests maybe

· may resemble a lymph node

· Thick pseudocapsule

· Germinal centres

· Plump to spindled histiocytic cells

· Hemorrhagic cyst-like spaces

· Resemble vascular spaces

· Not lined by endothelium

· Hemosiderin

·

· Aggregates of chronic inflammatory cells

· Lymphocytes

· Plasma cells

Immunophenotype:

Marker:	Sensitivity:	Specificity:
CD99
CD68	50%
Myofibroblastic markers	>50%

Molecular features:

· t(12;16)(q13;p11)

· FUS-ATF1 fusion gene

· t(12;22)(q13;q12)

· EWSR1-ATF1 fusion gene

· FUS on16p11

· Proliferative responses of B cells to mitogenic stimuli

· Maintenance of genomic stability

· Also involved in translocations of AML, low-grade fibromyxoid sarcoma, myxoid liposarcoma

· ATF on 12q13

· Transcription factor

· Also rearranged in clear cell sarcoma

· EWSR1 on 22q12

· Also rearranged in Ewing’s with multiple partners, intra-abdominal desmoplastic small round cell sarcoma, myxoid chondrosarcoma

Other features:

· Low-grade malignancy

· Slow growth

· Local recurrence (11%)

· Rare metastasis (1%)

· Mistaken for hematoma or hemangioma clinically

References:

· Vicente-Dueñas, Sánchez-García I . Angiomatoid Fibrous Histiocytoma (AFH). Atlas Genet Cytogenet Oncol Haematol. October 2005 . URL : http://AtlasGeneticsOncology.org/Genes/AngiomFibHistiocytID5204.html