<===> input.scss
.parent-sel-value {
  font-family: &;
  .parent-sel-interpolation {
    font-family: #{&};
     .parent-sel-value-concat {
        font-family: "Current parent: " + &;
     }
  }
}

<===> output.css
.parent-sel-value {
  font-family: .parent-sel-value;
}
.parent-sel-value .parent-sel-interpolation {
  font-family: .parent-sel-value .parent-sel-interpolation;
}
.parent-sel-value .parent-sel-interpolation .parent-sel-value-concat {
  font-family: "Current parent: .parent-sel-value .parent-sel-interpolation .parent-sel-value-concat";
}