之后在不同切面补取了6块，镜下图像都很相似。

cd99  is a 30-32 kD cell surface glycoprotein encoded by a pseudoautosomal gene located on the X and Y chromosomes. It is expressed by a range of high grade malignancies.

Antibodies are effective on paraffin-embedded tissue5.

Immunohistochemical expression

Positivity takes the form of strong membrane staining.

• normal tissues:

  • cortical thymocytes: medullary thymocytes are usually negative

  • mature peripheral T and B cells are usually negative

  • pancreatic islet cells

  • urothelium

  • some squamous cells

  • columnar epithelial cells

  • fibroblasts

  • endothelial cells2

  • granulosa/Sertoli cells

• T-cell ALL: one T-cell acute lymphoblastic leukaemia6 and seven of 11 T-lymphoblastic lymphomas6. All 8 B-lymphoblastic lymphomas were negative6. Positivity correlates with positivity for TdT7.

• granulocytic sarcoma

• Ewing's sarcoma / PNETs: 13 of 15 Ewing's sarcomas and 14 of 15 PNETS 6

• islet cell tumours

• carcinoids

• small cell carcinoma of lung but not Merkel cell tumours

• rhabdomyosarcoma: 4 of 14 embryonal rhabdomyosarcomas using 12E76 . All 10 alveolar rhabdomyosarcomas were negative6.

• nephroblastoma

• leiomyosarcoma: 6 of 47 cases1

• synovial sarcomas: 41 of 85 cases1

• haemangiopericytomas: 21 of 33 cases1

• malignant fibrous histiocytoma: 9 of 24 cases1

• meningiomas

• Superficial acral fibromyxoma

• solitary fibrous tumours1

• mesenchymal chondrosarcoma

• small cell osteosarcoma

• rarely mesotheliomas: 1 of 10 cases1

• uterine tumours with sex cord differentiation (1/23, 7/74)

• Leydig cell tumour of testis and occasional Sertoli cell tumour of testis

• Sertoli cell tumours of the ovary

• Atypical fibroxanthoma

Diagnostic utility

• Identification of immature lymphocytes in the diagnosis of thymoma

• Diagnosis of precursor T-cell and B-cell lymphoma/leukaemia

• PNET / Ewing's sarcoma

CD 56