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Diagnosing Melanoma: D is for Different

<p><span>Abandoning "Diameter"</span></p>

Abandoning "Diameter"

Melanoma, a potentially deadly skin cancer, can be cured by early detection and thorough surgical removal. Earlier detection has been strongly associated with improved survival of stage I melanoma (Conic). Self-examination is incredibly important, as demonstrated by a 63% relative reduction in deaths from melanoma in patients who find the melanoma themselves (Berwick).



The ABCD criteria were first proposed in 1985 as a guide to help physicians recognize suspicious lesions. (Friedman) The mnemonic was developed to be memorable, but also with the stated goal of diagnosing melanoma earlier. It has been subsequently adopted by organizations and individuals and has helped spread melanoma detection awareness. It has likely saved lives. The original mnemonic is A for asymmetry, B for border irregularity, C for color variation, and D for diameter greater than 6 mm. It is useful and memorable with one glaring flaw. Criticism of diameter as a criterium was expressed soon after the mnemonic was proposed.


In 1993, a 5th criterium, E for “evolution” was added. This would account for changing nature of melanomas over time. Also, the authors of the original criteria gave an explanation for diameter: the findings of asymmetry, border irregularity, and color variation are most consistently found when the diameter of a melanoma is greater than 6 mm, leading to a more facile diagnosis. (Rigel)


Unlike the largely subjective asymmetry, border irregularity, color variation, and evolution criteria, diameter is an objective measurement. It can easily lead patients astray. Patients and physicians might erroneously believe that a lesion equal to or less than 6 mm is benign and delay evaluation and potentially curative treatment.


Of course, it is easier to find larger melanomas. It is preferable to find them when they are small.

In fact, the point of melanoma detection is to find them as early as possible and surgically intervene, giving the patient the best chance of survival.


Small Melanomas

Subsequently, multiple reports of series of small melanomas led to substantiation of the intuitive fact that melanomas often occur that are equal or less than 6 mm in size. (Gonzales, Shaw, Bono, Kamino) Further, it could be argued that all melanomas start at a single or a few number of malignant cells, whose diameter is very small indeed. (Marine) Melanoma may also arise within existing nevi that are variable in size. (Duman) In a retrospective study, 206 pigmented lesions less than or equal to 3 mm that were clinically suspicious were investigated. 23 were melanomas; 4 in situ and 19 invasive with a depth between 0.2 and 1.08 mm. The authors stated that color is most important and did not consider dimension as a diagnostic criterium. (Bono)


The original authors of the ABCD criteria revisited the issue in 2004, once again insisting on the validity of diameter as a diagnostic tool. (Abbasi)


In 2011 the Georgia Society of Dermatology proposed that D should stand for “dark” and an additional “ugly duckling” sign be added to the diagnostic criterium. However, melanomas are not always dark. Others have pointed out that frequent modifications of the mnemonic could further add to diagnostic confusion (Maley).


The Ugly Duckling

The “ugly duckling” sign has been validated as a diagnostic clue. It is a mole different than other moles on a patient, just as a cygnet looks different than ducklings in the Hans Christian Andersen fairy tale. Patients who are instructed in the ugly duckling sign show higher specificity and accuracy for melanoma detection. The authors recommend including it as a diagnostic sign for melanoma recognition (Ilyas).


By 2013, the American Academy of Dermatology guide to melanoma diagnosis, explaining the ABCDE rule, noted that “melanomas are usually greater than 6 mm when diagnosed, but they can be smaller.” Such a qualification for an objective measurement is confusing and not useful. Additionally, though melanomas may be more often and more easily diagnosed at >6 mm does not abrogate the urgency to diagnose them earlier.


Later, after ongoing critique of diameter, the issue was again revisited in 2015. Again, the American Academy of Dermatology missed an opportunity to set the record straight. Multiple authors were involved, several that were on the original paper, which was the 4th time they commented on the size criterium. They reviewed the criteria, with an emphasis on diameter, to address criticism that has continued over three decades. The article states that “a significant percentage of melanoma may be less than 6 mm and may not be detected solely through use of diameter criteria.” However, instead of rejecting diameter, they quadrupled down, stating that there is not sufficient evidence to abandon D for diameter. (Tsao)



As Goldsmith and Cognetta stated (also in 2015), “the committee report evades the critical discussion of the likelihood that the 6 mm diameter criterion actually deters recognition of the earliest melanomas, a reality even the criteria authors acknowledged as obvious 20 years ago.”


With the general acknowledgement that melanomas can be of variable size, and earlier detection is best, diameter should be completely dispensed with as a diagnostic criterium. In place, the ugly duckling sign should be substituted for D. This can be abbreviated as D for “different.” Is the mole different than the other moles on the patient? This removes an arbitrary objective measurement that should not have been included. In its place is a criterium that has proven value in recognizing melanomas earlier.


References and further reading

Pediatric melanomas, while rare, are rather different than adult melanomas and lack the classic criteria. Authors have proposed using a de novo lesion of any diameter as a criterium. (Carrera) It is ironic that they include “any diameter” as a criterium, emphasizing the lack of utility of size. Once again, diameter is discounted.

Friedman RJ, Rigel DS, Kopf AW. Early detection of malignant melanoma: the role of physician examination and self-examination of the skin. CA Cancer J Clinical.1985;35(3):130-51.

Marghoob AA, Slade J, Kopf AW, et al. The ABCDs of melanoma: why change? JAAD:1995;682-4

Gonzales A, West AJ, Pitha JV et al. Small diameter invasive melanomas: clinical and pathologic characteristics. J Cutaneous Path 1996:23(2):126-32.

Branstrom R, Hedblad MA, Krakau I, et al. Laypersons perceptual discrimination of pigmented skin lesions. JAAD. 2002;46:667-73.

Abbasi NR, Shaw HM, Rigel DS, et al. Early diagnosis of cutaneous melanoma: revisiting the ABCD criteria. JAMA. 2004;292(22):2771-6.

Bono A, Tolomio E, Trincone S, et al. Micro-melanoma detection: a clinical study on 206 consecutive cases of pigmented skin lesions with a diameter </= 3 millimeters. Brit J Derm. 2006:155;570-3.

Hill D. Editorial: health promotion programs for melanoma prevention. Arch Derm. 2008:144(4);538-40.

Duman N, Erkin G, Gokoz O. et al. Nevus associated versus de novo melanoma: do they have different characteristics and prognoses? Dermatopathology; 2015;2(1):46-51.

Tsao H, Begolka WS. Reply to: time to move forward after the report of the AAD task force for the ABCDEs of melanoma. JAAD. 2015:e151.

Goldsmith SM, Cognetta AB. Time to move forward after the report of the AAD task force for the ABCDEs of melanoma. JAAD. 2015:e149-50.

Maley A, Rhodes AR. is a preoperative tumor diameter of 6 mm or less reliable in excluding a diagnosis of melanoma? JAAD. 2015:e75

Tsao H, Begolka WS. Reply to: “the ABCDs of melanoma-- a complicated morphologic message not intended for the General Public.” JAAD. 2015:e61.

American Academy of Dermatology ad hoc task force for the ABCDEs of melanoma. Early detection of melanoma: reviewing the ABCDEs. JAAD 2015;72:717-23.

Ilyas M, Costello CM, Zhang N, et al. The role of the ugly duckling sign in patient education. JAAD. 2017:77(6);1088-1095.

Marine JC et al. Mouse cutaneous melanoma induced by mutant BRaF arises from expansion and dedifferentiation of mature pigmented melanocytes. Cell stem cell: 2017.

Conic RZ, Cabrera CI, Khorana AA, et al. Determination of the Impact of Melanoma Surgical Timing on Survival using the National Cancer Database. JAAD. 2018:78(1);40-46.

Carrera C, Scope A, Dusza SW, et al. Clinical and Dermoscopic characterization of Pediatric & Adolescent melanomas: Multicenter study of 52 cases. JAAD. 2018:78(2);278-88.

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