The number of people waiting more than six weeks for key medical tests has increased by almost 350% in just two years, new figures revealed, prompting cancer charities to call for urgent action.
At the end of December 2017 15,956 people were waiting longer than the target time for diagnostic procedures such as CT scans, MRI scans and ultrasounds.
That compares to 3,554 at December 31 2015, and while the number of people on the list for tests rose 47.6% to 77,256 over the period, there was an increase of 348.9% in the number waiting more than six weeks for the checks.
Gregor McNie, Cancer Research UK's senior public affairs manager in Scotland, said the latest health service figures "paint a picture of a service struggling to keep up with growing demand".
He stated: "Waiting to find out if you do or don't have cancer can cause huge anxiety to patients.
"Staff shortages are partly to blame and the recent initiative to recruit more radiologists will go some way to alleviate current pressures.
"But a more urgent plan for all diagnostic staff is also needed."
Janice Preston, head of Macmillan Services in Scotland, stated: "To wait more than six weeks for that critical test must seem like an eternity filled with stress and anxiety.
"Ensuring that people are diagnosed as quickly as possible is vital in both supporting patients and boosting the chances of survival.
"Cancer waiting times haven't been met since 2012 and these latest statistics add to a growing issue that must be addressed head on and a solution found.
"While action has been taken, we want to work with the Scottish Government to face the challenge of supporting the vastly increasing number of people with cancer."
According to the figures the number of people being tested within six weeks has fallen from 94.7% in February 2016 to a low of 79.3% in December 2017.
Meanwhile the number of people waiting more than six weeks for an endoscopy - where a tiny camera is inserted into the body on a thin tube - has gone from 2,563 in June 2016 to a high of 11,105 at 31 December 2017.
Health Secretary Shona Robison said: "The Scottish Government has made £4.85 million of funding available to support access to diagnostics for suspected cancer patients, including £2 million for improvements to scopes alone.
"I have made it clear to Boards that they must continue to treat these patients with the highest priority."
The figures were released at the same time as separate statistics showing that in December 2017, 82.5% of patients went from referral to treatment within the target time of 18 weeks - not including NHS Tayside which failed to provide figures.
The Scottish Government standard of having 90% of patients go from referral to treatment in this time has not been met since July 2014.
There has also been an increase in the number of people waiting more than 12 weeks for an outpatient appointment at hospital or treatment as either an inpatient or a day patient.
At the end of December last year 95,922 people had been waiting over 12 weeks for a new outpatient appointment, up from 73,857 in December 2016 and 33,221 in the same month in 2015.
There were 13,927 people who waited more than 12 weeks for inpatient or day treatment in December 2017, up from 9,805 the previous year and 3,754 in December 2015.
Labour health spokesman Anas Sarwar hit out, saying: "The SNP made a promise - in fact ministers made a legal guarantee - that inpatient or day case treatment patients would receive treatment within 12 weeks for certain conditions.
"Instead new figures reveal that promise has been broken and that performance is sliding.
"A decade of SNP mismanagement has left our NHS under staffed an under pressure. Patients aren't getting the care they deserve because staff aren't getting the support they need."
But Ms Robison stated: "It is testament to hard-working staff right across the NHS that, despite winter pressures, almost 351,000 patients were seen and treated by NHS Boards, up 3% on the last quarter."