Morphology & Grade

Major Cellular Classifications for Non-Hodgkin Lymphomas (now considered obsolete)

6th Digit Morphology (Grade/Differentiation)

The sixth digit (behavior/differentiation) of the morphology code can be added to the cell types of lymphomas that have been identified by surface marker studies. Code any statement of T-cell or B-cell involvement whether or not marker studies are documented in the patient record.

1. Well differentiated
2. Moderately differentiated
3. Poorly differentiated
4. Undifferentiated
5. T-cell
6. B-cell
7. Null cell (no longer for leukemias only)
8. NK cell (new for 1995 cases and after)
9. Not determined, not graded

Guidelines

For lymphomas, information on T-cell and B-cell has precedence over information on grading or differentiation.

The term "phenotype," as in B-cell phenotype, indicates the type or origin of the tumor. This information can be used to assign the 6th digit B-, T-, or NK-cell code.

Do not code grade 1, 2, or 3 for Hodgkin lymphoma, nodular sclerosing or follicular lymphoma in the 6th digit grade field.

For lymphomas, do not code the descriptions "high grade," "low grade," or "intermediate grade" in the 6th digit grade or differentiation field. These terms refer to categories in the Working Formulation and not to histologic grade.

Most lymphoblastic lymphomas are T-cell. With the exception of the immunoblastic large cell lymphomas and the mixed small and large cell diffuse lymphoma, most of the rest are B-cell.

The following lymphoma morphologies and codes were added to ICD-O-2 starting with Jan. 1, 1995 diagnoses:

Classification Systems for Hematopoietic and Lymphoid Neoplasms

• Rappaport Classification
• Rye Classification
• Kiel Classification
• Working Formulation
• REAL Classification
• WHO Classification