Mass. Gen. Laws ch. 59, § 12E

The real estate of a person deceased, the right or title to which is doubtful or unascertained by reason of litigation concerning the will of the deceased or the validity thereof, may be assessed in general terms to his estate, and said tax shall constitute a lien upon the land so assessed and may be enforced by sale of the same or a part thereof, as provided for enforcing other liens for taxes on real estate.