Tenosynovial giant cell tumor (TGCT) is the most common benign tumor of synovium and tendon sheath.

Synopsis

 sharply circumscribed
 lobulation by fibrous septa
 round or polygonal histiocytic or fibrohistiocytic cell
 giant cells (multinucleated histiocytes) usually present
 +/- osteoclastic type giant cells
 foamy histiocytes
 hemosiderin laden histiocytes

Types

 localized TGCT (nodular tenosynovitis)
 diffuse TGCT (pigmented villonodular synovitis)

Immunochemistry

 histiocytic cells

• CD68+
• +/- factor XIIIs
• +/- actins
• +/- desmin

 multinucleate cells

• CD68+
• LCA+

Differential diagnosis

 foreign body granuloma
 necrobiotic granuloma
 tendinous xanthoma
 fibroma of the tendon sheath
 epithelioid sarcoma
 biphasic synovial sarcoma

Cytogenetics

 1p11 to 1p13.2 structural rearrangements (#8780753#)

• t(1;1)(q21;p11) (1q21 and 1p11) (#15548367#)
• t(1;2)(p11;q35-36) (1p11 and 2q35-q36) (#8033128#)
• t(1;5)(p11;q22) (1p11 amd 5q22) (#8033128#)
• t(1;19)(p11;p12) (1p11 and 19p12) (#7685623#)
• t(1;22)(p13;q12) (1p13 and 22q12) (#15548367#)
• t(1;2)(pter->p22::q24->pter) (#7631554#)
• t(1;14)(qter->p13::q13->ter) (#7631554#)

 1q21 structural rearrangements

• t(1;1)(q21;p11) (1q21 and 1p11) (#15548367#)

 2q33-2q35-2q36-2q37 structural rearrangements

• t(2;16)(q33;q24) (2q33 and 16q24) (#8033128#)
• t(1;2)(p11;q35-36) (1p11 and 2q35-36) (#8033128#)

 16q24 structural rearrangements

• t(2;16)(q33;q24) (2q33 and 16q24) (#8033128#)
• t(7;16)(q22;q24) (7q22 and 16q24) (#7685623#, #8646750#)

• translocation partner
  • 2q35-37
  • 5q22-31
  • 8q21-22
  • 11q11-12

 other translocations

• t(2;4)(p23;q21) (2p23 and 4q21) (#7685623#)

 trisomies

• trisomy 5
• trisomy 7 (57%) (#15548367#, #11734313#)

CGH (#15766598#)

Gains

16p

16q

22q

Molecular biology

Prognosis

 benign
 local recurence rate: 10%

References

 Brandal P, Bjerkehagen B, Heim S. Molecular cytogenetic characterization of tenosynovial giant cell tumors. Neoplasia. 2004 Sep-Oct;6(5):578-83. PMID: #15548367# (Full text free)

 Rowlands CG, Roland B, Hwang WS, Sevick RJ. Diffuse-variant tenosynovial giant cell tumor: a rare and aggressive lesion. Hum Pathol. 1994 Apr;25(4):423-5. PMID: #8163276#