pericytic tumors

This group of tumours has previously been more closely grouped with vascular (endothelial) tumours.

However, now that it has been recognized that most examples of so-called haemangiopericytoma are in fact fibroblastic lesions better classified as solitary fibrous tumour, the tumours which remain in this category, which are composed of perivascular contractile cells, are clearly more closely related to smooth muscle neoplasms, hence the shift of this category within the overall classification system.

All of the lesions remaining in the pericytic/perivascular category show clear evidence of myoid differentiation and all share the characteristic tendency to grow in a circumferential fashion around blood vessels.

Cytogenetics

 translocation t(7;12)(p22;q13) (7p22 and 12q13) in pericytomas

• The t(7;12)(p22;q13), fuses the ACTB gene in 7p22, to the GLI1 gene in 12q13 (ACTB/GLI1 fusion gene)

Molecular biology

 ACTB/GLI1 fusion gene by translocation t(7;12)(p22;q13)

• fusion of ACTB gene in 7p22 with GLI1 gene in 12q13

References

 The evolving classification of soft tissue tumours: an update based on the new WHO classification. Fletcher CD. Histopathology. 2006 Jan;48(1):3-12. PMID: 16359532

 Dahlin A, Fletcher CDM, Mertens F, Fletcher JA, Perez-Atayde AR, Hicks MJ, Debiec-Rychter M, Sciot R, Wejde J, Wedin R, Mandahl N, Panagopoulos I. Activation of the GLI oncogene through fusion with the beta-actin (ACTB) gene in a group of distinctive pericytic neoplasms: Òpericytoma with t(7;12). Am J Pathol 2004; 164: 1645-1653 PMID: 15111311

 Dahlin A, Mertens F, Mandahl N, Panagopoulos I. Molecular genetic characterization of the ACTB-GLI fusion in pericytoma with t(7;12). Biochem Biophys Res Commun 2004; 325: 1318-1323. PMID: 15555571