Missed or delayed melanoma diagnosis

Melanoma is a cancer that begins in melanocytes, the cells that make the pigment melanin (opens in a new tab), and it may begin in a mole. The National Cancer Institute says its signs include a change in the way a mole or pigmented area looks (opens in a new tab), and that these signs may be caused by melanoma or by other conditions.

The diagnosis is made on tissue. The Institute describes a biopsy as the removal of cells or tissues so they can be viewed under a microscope (opens in a new tab). The doctor who reads them is a pathologist.

Screening means examining people who have no symptoms. On April 18, 2023 the U.S. Preventive Services Task Force concluded that the current evidence is insufficient to assess the balance of benefits and harms of visual skin examination by a clinician (opens in a new tab) to screen adolescents and adults for skin cancer.

The Task Force calls that an I statement, its term for evidence that is lacking, of poor quality, or conflicting (opens in a new tab). In its words there is insufficient evidence to recommend for or against screening (opens in a new tab), and the statement creates no legal duty.

The screening statement does not cover that. The Task Force says it does not apply to symptomatic patients, including those who present with a suspicious skin lesion (opens in a new tab). What a clinician should do for such a patient is a question of careful practice.

The National Cancer Institute tells patients that it can be hard to tell the difference between a colored mole and an early melanoma (opens in a new tab), and that they may want to have the sample of tissue checked by a second pathologist.

Neither a screening statement nor a patient summary is a rule. What careful practice required in a particular case is for a qualified physician to explain.

One place is the slide. In a 2017 study, 187 U.S. pathologists read biopsies of moles and melanomas that a panel of experienced pathologists had classified. The authors estimated that, in the population at large, 82.8% of such diagnoses would be verified by a panel of that kind, 8.0% would be found to overstate the lesion and 9.2% to understate it (opens in a new tab). The yardstick was expert agreement, which is not proof of what the lesion was.

Agreement was weakest for lesions ranging from moderately abnormal moles to early invasive melanoma. Reading the same slide a second time, a pathologist repeated the first diagnosis 35.2% to 63.2% of the time for lesions in that range (opens in a new tab), in a set of slides weighted toward difficult cases. So a melanoma found after an earlier biopsy was read as benign is not, for that reason alone, a missed melanoma.

Among 362 pathology malpractice claims reported to one insurer from 1995 through 2001, 46 involved the misdiagnosis of melanoma, or 13%, and 70% of those were for a melanoma that was not diagnosed (opens in a new tab).

A caution applies to those figures. They count claims reported to one insurer more than two decades ago. They are shares of claims, and they say nothing about how often a melanoma is misread among patients in general.

The research stops short of a firm answer. A 2015 review of studies of time to diagnosis in patients with symptoms named melanoma among the cancers with more reports of an association between shorter times to diagnosis and more favorable outcomes (opens in a new tab). It also said that differences among the studies precluded definitive findings.

A 2018 study of a national cancer database looked at the wait between biopsy and surgery. In stage I, the earliest of the stages studied, a longer wait was associated with a higher risk of death (opens in a new tab). In stages II and III, the timing of surgery did not affect survival.

That study measured delay in treatment after a biopsy had already shown melanoma. It did not measure delay in reaching the diagnosis, and it counted deaths from any cause.

In Illinois a patient has to prove that the care was negligent and that the negligence more probably than not caused the harm, which can be a lost chance of a better outcome. That takes expert proof in each case.

Three things held by a laboratory matter most: the glass slides the pathologist read, the block of tissue, and the pathology report. Federal rules set a minimum period for each.

A laboratory must keep the slides of biopsy tissue for at least 10 years from the date of examination, and the tissue blocks for at least 2 years (opens in a new tab). It must keep pathology reports for at least 10 years after the date of reporting (opens in a new tab). The block has the shortest minimum.

You can ask for copies of your reports, and how to request records under Illinois law is on our law page. It helps to write down the date of each visit and biopsy, and what you were told about the result.