The State House in Augusta.

A southern Maine state representative who was diagnosed last year with lung cancer said Tuesday he would be resigning from his post this week.

Rep. Dale Denno, D-Cumberland, said he made the decision to resign, effective Wednesday, with “sadness and gratitude.”

Denno, a Democrat who serves House District 45, was re-elected for a second term in November. Soon after his diagnosis last August, he vowed, with his doctor’s approval, not to let his recent lung cancer diagnosis derail his intention to hold state office.

Credit: Maine House of Representatives

“Based upon initial medical advice, as well as strong energy and good spirits, I decided to continue representing the great people of Cumberland and Gray,” Denno said in a statement Tuesday.

But, he said, during the past few weeks, “it has become apparent that it is no longer realistic for me to continue in my current role as state representative, and I only want the best representation for the people of House District 45.”

Denno, who did not immediately return a phone call early Tuesday afternoon, said in the statement that serving his district “has been one of the greatest honors of my life.”

“I will always be grateful to my friends and colleagues in the Legislature, and especially the folks in Cumberland and Gray for placing their confidence in me and offering me nothing but the best wishes in good times and bad,” Denno said.

In a separate statement, Democratic Gov. Janet Mills called Denno a “tireless champion for his constituents” and House Speaker Sara Gideon, D-Freeport, called him a “passionate public servant.”

A special election to fill Denno’s seat will likely be held in June. Republicans, Democrats and Green Independents from the district will be able to caucus to choose candidates for the special election. Former Democratic state Rep. Steve Moriarty has expressed interest in running to succeed Denno, according to Sean Smith of the Maine House Democratic Campaign Committee.

Denno is the third Democrat elected to the House last November to leave his seat. Aaron Frey of Bangor chose not to be sworn in after he won a fourth term because legislators elected him to be Maine’s attorney general. Jennifer DeChant, D-Bath, resigned Feb. 1 to take a private-sector job.

Rep. Joe Perry, a Democrat, won the March 12 special election to succeed Frey. Voters in Bath will elect DeChant’s successor April 2.

Prior to winning election to the Legislature, Denno worked for years for the Maine Department of Health and Human Services, including a stint as director of the State Office of Family Independence.