In ICD-O coding, which statement correctly describes the morphology component?

• A. It encodes the cell type and uses four digits
• B. It encodes the tumor grade and uses two digits
• C. It encodes the site of metastasis and uses three digits
• D. It encodes patient demographics and uses five digits

Answer: (A)

Morphology in ICD-O represents the tumor’s histology—the specific cell type and how the tumor cells appear under the microscope. It is encoded with a four-digit histology code, usually shown with a behavior digit after a slash to indicate malignant, in situ, or benign behavior. This is why the statement that the morphology component encodes the cell type and uses four digits is correct. Other aspects like the site of metastasis relate to topography, tumor grade isn’t part of the four-digit histology code, and patient demographics aren’t encoded in this morphology component.