IMMUNOHISTOCHEMISTRY, CD 99 (MIC-2)

The IHC – CD99 (MIC-2) test is an immunohistochemistry-based diagnostic test used to detect CD99 protein expression in tissue samples. CD99, also known as MIC2, is a transmembrane glycoprotein that is strongly expressed in certain types of tumors, especially Ewing sarcoma and primitive neuroectodermal tumors (PNETs).

This test plays a crucial role in pathology for identifying small round cell tumors, a group of aggressive cancers that can be difficult to differentiate using routine microscopy alone. CD99 shows a characteristic membranous staining pattern, which helps pathologists confirm tumor type and origin.

Benefits of the Test

• Helps diagnose Ewing sarcoma and PNETs
• Assists in identifying small round cell tumors
• Improves tumor classification accuracy
• Supports differentiation from other similar malignancies
• Aids oncologists in treatment planning

Why Doctors Recommend This Test

Doctors recommend the IHC CD99 test when a biopsy shows a poorly differentiated or small round cell tumor. It is commonly used in:

• Suspected Ewing sarcoma cases (bone or soft tissue tumors)
• Pediatric and adolescent bone tumors
• Undifferentiated malignant tumors
• Differential diagnosis of small round cell tumors
• Oncology staging and confirmation studies

CD99 is not completely specific on its own, so it is usually used along with other markers such as FLI-1, NKX2.2, CD45, and cytokeratins to achieve a precise diagnosis.

Preparation Before Test

No special preparation is required for the patient. Key points include:

• The test is performed on a biopsy or surgical tissue sample
• No fasting or medication restrictions are needed
• Clinical history is important for interpretation

Normal Reporting Time

The reporting time is typically 3 to 5 working days, depending on laboratory workload and sample complexity.

Who Should Take This Test

• Patients with suspected Ewing sarcoma
• Individuals with bone or soft tissue tumors
• Cases of small round cell tumors of unknown origin
• Pediatric and adolescent tumor evaluations
• Oncology diagnostic confirmation cases

The IHC CD99 (MIC-2) test is an important tool in modern diagnostic pathology. It helps pathologists identify aggressive tumors accurately, ensuring correct classification and timely treatment planning.