A Wellington teacher died in her sleep on Monday from an undiagnosed brain tumour, Dominion Post reports.

Thirty-nine year old Lorena Henriquez, a single mother and a positively popular teacher among her students, had felt flu-like symptoms for three days before succumbing to cancer while sleeping.

Wellington High School principal Nigel Hanton told Dominion Post many pupils were taking up the school's offer of counselling to deal with the sudden loss of the well-loved Spanish and English teacher.

Lorena's close friend Emily Telfer said she could be described as "fearless and fabulous...she just lived life completely to the full."

Dominion Post spoke to Lorena's brother Jose Henriquez, who said the family were shocked at the sudden passing of his loving sister, and they were devastated for her son Saul, 14.

Lorena had shown flu-like symptoms since Thursday, and had called in sick on Friday. She had seemed to be feeling better on Sunday, Mr. Henriquez said, adding their mother called emergency services when she found Lorena unresponsive at 7:30am on Monday morning.

Mr. Henriquez said their family did not notice anything seriously wrong other than the flu like symptoms that seemed to have gotten better a day before his sister died.

"She was a warm, lovely, bubbly person, very, very caring... She could just about get on with anyone which was fantastic, she loved to talk and she loved music. It's just a tragic loss."

Chile-born Lorena had moved to Johnsonville with her family in 1978. Stricken with wanderlust, she had travelled to Europe, Korea, and South America, among other countries.

She was a reliever at many Wellington schools before joining Wellington High School in 2010.

In this forum over three years ago, an unnamed cancer patient narrated that his/her cancer was diagnosed after a consult with the doctor over his/her sleeping problems.

In cancerhelp.org, drowsiness is listed as one of the symptoms of brain tumour. A person with brain tumour may sleep more than usual, and may even doze off irregularly during the day. If not treated, the drowsy person with a brain tumour may have difficulty waking.

Headaches and fits are the most common symptoms of a brain tumor. A fit, according to cancerhelp.org, "can just be jerking or twitching of a hand, arm or leg."

An estimated 24,000 people in the United States are diagnosed each year with a malignant brain or spinal cord tumor, according to the American Cancer Society.