diff --git a/resources/cql/DKTK_REPLACE_HISTOLOGY_STRATIFIER b/resources/cql/DKTK_REPLACE_HISTOLOGY_STRATIFIER
new file mode 100644
index 0000000..b7b70d3
--- /dev/null
+++ b/resources/cql/DKTK_REPLACE_HISTOLOGY_STRATIFIER
@@ -0,0 +1,4 @@
+define Histo:
+if InInitialPopulation then [Observation] else {} as List <Observation>
+
+define function Histology(histo FHIR.Observation):