Cobblestone Area-Forming Cells

**Semantic type:** Laboratory Procedure

**Definition:** The number of hematopoietic stem cells (HSCs) that migrate between or beneath a co-cultured feeder cell layer and become trapped. When HSCs are cultured with a feeder layer and observed using phase contrast microscopy, the trapped cells appear less spherical and less refractile than the HSCs that are floating loosely on top of the feeder layer.

**Synonyms:** - CAFC - Cobble Stone Area-Forming Cells - Cobblestone Forming Units