Module 07: TADA and Other Triage Algorithms

Triage refers to the sorting and classification of lesions to determine which require biopsy or referral. The primary goal is to avoid missing skin cancer (maximize sensitivity). Making a specific histological diagnosis (e.g., distinguishing BCC from SCC from melanoma) is a secondary objective during triage.

Different algorithms serve different purposes, populations, and settings:

• Triage algorithms (TADA, three-point checklist, AC rule, blue-black rule, Chaos and Clues) prioritize high sensitivity to avoid missing cancers.
• Differentiation algorithms (ABCD rule, Menzies method, seven-point checklist, CASH) use semi-quantitative scoring to distinguish benign from malignant among lesions already flagged as suspicious.
• Site-specific algorithms (BRAAFF) address unique anatomic locations such as volar skin.

Virtually every dermoscopic algorithm includes asymmetry (of color, structure, or both) as a core criterion. Asymmetry in the distribution of dermoscopic colors and structures is the single most reproducible and powerful predictor of malignancy across all algorithms.

All algorithms have trade-offs between sensitivity and specificity. Newer structures (shiny white lines, negative network, angulated lines) identified since the original publication of many algorithms have not yet been formally incorporated, and clinicians should not ignore these features when using any algorithm.

---

Architecture and Philosophy

The Triage Amalgamated Dermoscopic Algorithm (TADA) is a three-step algorithm created by Jaimes, Marghoob, and colleagues to provide a simple method for guiding management decisions about whether a lesion should undergo biopsy or be referred to an expert clinician. TADA is specifically a triage algorithm that incorporates key criteria for malignancy derived from multiple existing algorithms.

Key design principles:

• TADA amalgamates criteria from established algorithms (ABCD rule, three-point checklist, Chaos and Clues, blue-black rule, AC rule) into a single streamlined workflow.
• It was designed and tested on lesions located on non-glabrous skin only. It cannot be used on lesions on volar surfaces, nails, or mucosae.
• It requires polarized light dermoscopy for Steps 2 and 3.

Performance Data

TADA has been tested in reader studies with clinicians and nurse practitioners:

Metric	Range
Sensitivity	88.1% -- 94.8%
Specificity	72.3% -- 87.8%

(Rogers et al., 2016; Seiverling et al., 2019)

TADA Algorithm Flowchart

flowchart TD
 A[Lesion Identified] --> B{Step 1: Unequivocal<br/>SK, Angioma, or DF?}
 B -->|Yes| C[Benign -- Reassure<br/>Patient]
 B -->|No| D{Step 2: Pattern<br/>Organized or<br/>Disorganized?}
 D -->|Disorganized| E[Suspicious --<br/>Biopsy]
 D -->|Organized| F{Step 3: Any of<br/>2 Patterns, 2 Structures,<br/>or 4 Colors?}
 F -->|Starburst or<br/>Negative Network| G[Biopsy<br/>Recommended]
 F -->|Vessels or<br/>Ulceration| G
 F -->|Blue, Black,<br/>Gray, or White| G
 F -->|None Present| H{Lesion<br/>Palpable?}
 H -->|No| I[Monitor with<br/>Digital Dermoscopy]
 H -->|Yes / Raised| J[Consider Excision]

Three-Point Checklist Flowchart

flowchart TD
 A[Pigmented Lesion] --> B{1. Asymmetry of<br/>color/structures?}
 B -->|+1 point| C{2. Blue-white<br/>structures?}
 B -->|0 points| C
 C -->|+1 point| D{3. Atypical<br/>network?}
 C -->|0 points| D
 D -->|+1 point| E[Calculate Total<br/>Score]
 D -->|0 points| E
 E -->|Score >= 2| F[Biopsy or Referral<br/>Recommended]
 E -->|Score 0-1| G[Low Suspicion --<br/>Monitor]

Step-by-Step TADA Application

TADA Step 1: Is the Lesion an Unequivocal Seborrheic Keratosis, Angioma, or Dermatofibroma?

The observer first determines whether the lesion fulfills the clinical and dermoscopic criteria for an unequivocal benign lesion from one of the three most commonly encountered categories:

1. Seborrheic keratosis (SK) -- gyri and sulci (ridges and fissures), milia cysts, comedo-like openings, cerebriform pattern, well-demarcated borders
2. Angioma -- red or blue-black lacunae separated by septae
3. Dermatofibroma (DF) -- peripheral network with a central scar-like area, ring-like structures

If unequivocally benign: Reassure the patient. No further evaluation required.

If not unequivocally benign: Proceed to Step 2.

Clinical Note: Less common benign lesions (clear cell acanthoma, molluscum, xanthogranuloma, etc.) are not formally included in TADA Step 1. However, experienced clinicians who can confidently identify other benign entities may add them to the Step 1 list.

TADA Step 2: Does the Lesion Manifest a Disorganized Pattern?

Only lesions that are not unequivocally benign proceed to Step 2, which requires polarized light.

The observer assesses whether the lesion demonstrates an organized or disorganized pattern. Dermoscopic patterns take into account the distribution of colors and structures within the lesion.

• Disorganized pattern (chaotic distribution of colors and structures): Lesion is considered suspicious -- perform skin biopsy.
• Organized pattern: Proceed to Step 3.

Asymmetry (chaos or disorganized pattern) is the most important characteristic to help differentiate benign from malignant tumors. It is reproducible and demonstrates the highest inter-observer agreement.

TADA Step 3: Does the Organized-Appearing Lesion Manifest One of Two Patterns, Two Structures, or Four Colors?

Only equivocal lesions demonstrating an organized pattern proceed to Step 3, which also requires polarized light.

The observer evaluates for the presence of any of the following features:

1. Any one of two patterns:

Pattern	Description	Significance
Starburst pattern	Streaks or globules forming a starburst (radial) arrangement	Can be seen in Spitz/Reed nevi but also in melanoma. Suspicious especially in individuals over age 12 years. Biopsy recommended.
Negative network pattern	Serpiginous negative (lighter) network throughout the lesion	Both Spitz nevi and melanomas can display this pattern. Biopsy recommended.

2. Any one of two structures:

Structure	Description	Significance
Vessels	Any vascular structure of any morphology	Lesions revealing any vascular structures should be biopsied.
Ulceration	Ulceration or erosions	Suspect lesion; biopsy recommended.

3. Any one of four colors:

Color	Clinical Significance
Blue	Blue-black color has high sensitivity for nodular melanoma.
Black	Concerning when present in an organized lesion not clearly a benign entity.
Gray	Important clue for skin cancer, particularly melanomas on sun-damaged skin. Blue-gray granularity has strong association with melanoma.
White	Includes shiny white structures (polarizing-specific) and white circles. Shiny white lines/streaks are melanoma-specific; shiny white blotches and strands are BCC-specific; white circles are associated with well-differentiated SCC. Although some benign lesions (DF, LPLK, Spitz nevi) may show white structures, for triage purposes any white color should be viewed with suspicion.

Decision after Step 3:

• If any of the above features are present: Malignancy should be considered -- biopsy recommended.
• Additional considerations (outside the three-step flow):
• Lesions on volar skin (palms/soles) displaying a parallel ridge pattern should be considered suspicious.
• Any changing lesion in an adult should be considered suspicious for malignancy.
• If none of the above features are present and the lesion is nonpalpable: The lesion can be monitored (see digital monitoring approaches, Module 37).

Check Your Understanding

What does TADA stand for, and what is the key principle behind this algorithm?

TADA stands for Triage Amalgamated Dermoscopic Algorithm. Its key principle is simplification: rather than requiring identification of specific structures, TADA asks whether the lesion has any architectural disorder or is a 'gray, blue, or white' lesion. If the answer to either is yes, the lesion warrants biopsy or referral.

Clinical Scenario

A 56-year-old woman presents with a 7 mm pigmented papule on the right forearm that she noticed changing over 3 months. You apply the TADA algorithm. Step 1: the lesion is not an unequivocal SK, angioma, or dermatofibroma. Step 2: the overall pattern appears organized -- colors and structures are relatively symmetrically distributed. Step 3: you examine for the 2-2-4 criteria and find shiny white lines visible under polarized dermoscopy.

What is your diagnosis and key dermoscopic findings?

Suspicious lesion requiring biopsy (TADA Step 3 positive)

Despite the organized appearance (Step 2 negative), TADA Step 3 detects white structures (shiny white lines under polarized light), which is one of the four suspicious colors. Any one of the 2 patterns, 2 structures, or 4 colors in Step 3 is sufficient to recommend biopsy. White structures are a critical finding because shiny white lines can indicate melanoma (dermal invasion with stromal alteration) or BCC (shiny white blotches and strands from mucin and BCC matrix). This case demonstrates why Step 3 is essential -- organized-appearing malignancies would be missed without screening for these specific features.

---

Key Takeaways

• TADA (Triage Amalgamated Dermoscopic Algorithm) is designed for non-expert users and uses simple architectural disorder plus any specific feature to flag lesions for referral.
• The 3-point checklist (asymmetry, atypical network, blue-white structures) achieves high sensitivity and is suitable for primary care screening.
• The ABCD rule provides a quantitative total dermoscopy score (TDS) where scores above 5.45 indicate high melanoma probability.
• Menzies method requires both a negative feature (absence of symmetry and single color) and at least one of nine positive features for melanoma diagnosis.

Overview

Chapter 5c organizes triage algorithms into three categories based on lesion pigmentation:

Category	Algorithms
Pigmented lesions	Three-point checklist, AC rule, Blue-black rule, Chaos and Clues
Non-pigmented lesions	Prediction without Pigment (see Module 05)
Pigmented and non-pigmented	TADA

Overall, algorithms for pigmented lesions have a sensitivity of 78.2%--92.9% and a specificity of 64%--92.3% for the diagnosis of pigmented skin cancers including melanoma and BCC.

Limitation: Algorithms designed for pigmented lesions will not help detect amelanotic or hypomelanotic skin cancers. Since the main purpose of these algorithms is to avoid missing pigmented skin cancer, some benign pigmented lesions (thrombosed hemangiomas, angiokeratomas, pigmented SK) may be misclassified as suspicious and subjected to biopsy.

---

Three-Point Checklist

Purpose: Initially developed for non-experts as a skin cancer screening tool.

Criteria (one point each):

#	Criterion	Definition
1	Asymmetry	Asymmetry in the distribution of dermoscopic color and/or structures in one or two perpendicular axes. The contour or silhouette of the lesion does not factor into symmetry assessment.
2	Blue-white structures	Blue-white veil, and/or white scar-like depigmentation, and/or blue pepper-like granules.
3	Atypical network	Pigment network with thick lines and irregular-sized holes.

Scoring: One point per criterion present. A score of 2 or 3 = positive (biopsy or referral recommended).

Hierarchy of predictive value: Asymmetry in the distribution of colors and structures is the best predictor of malignancy, followed by blue-white structures, then atypical network.

Performance:

Metric	Range
Sensitivity (melanoma and BCC)	79% -- 91%
Specificity (melanoma and BCC)	71% -- 72%

Limitation: The three-point checklist was not developed to identify pigmented SCC. It is therefore recommended that any pigmented lesion with focal adherent keratin or a rough texture revealing an asymmetric dermoscopic pattern be considered suspicious to avoid missing pigmented SCC.

Check Your Understanding

What are the three criteria in the 3-Point Checklist, and how many must be present to warrant excision?

The three criteria are: (1) asymmetry of pattern, (2) atypical network (thick lines, irregular holes), and (3) blue-white structures. The presence of any two out of three criteria warrants excision or biopsy. This algorithm was designed for simplicity and is useful for less experienced dermoscopists.

---

AC Rule

Purpose: Developed as a simple rule to identify lesions suspicious for melanoma, suitable for the wider community including laypersons.

Criteria:

Letter	Criterion	Definition
A	Asymmetry	Asymmetry in the distribution of structures and colors.
C	Color variation	Multiple colors within the lesion, with black or blue-gray color being most suggestive of melanoma.

Scoring: Both criteria present = suspicious for melanoma.

Performance (tested in laypersons):

Metric	Value
Sensitivity (melanoma)	94%
Specificity (melanoma)	62%

---

Blue-Black Rule

Purpose: Proposed specifically to identify pigmented nodular melanomas, which often appear as symmetric papules or nodules and may be missed by algorithms relying heavily on asymmetry.

Definition: The blue-black feature is defined as the presence of a combination of blue and black areas involving at least 10% of the lesion surface area.

Exclusions: The blue-black feature is NOT counted when:

• Unequivocal comedo-like openings (as found in seborrheic keratosis) are present with the blue-black background.
• Dark lacunae (as seen in angiokeratomas) occur with the blue-black background.

Performance:

Metric	Value
Sensitivity (melanoma) -- blue-black rule alone	78.2%
Sensitivity (melanoma) -- blue-black rule + melanoma-specific structures	84.6%
Specificity (melanoma) -- blue-black rule alone	80.5%
Specificity (melanoma) -- melanoma-specific structures only	97.6%
Specificity (melanoma) -- both criteria combined	80.5%

Additional melanoma-specific structures evaluated alongside the blue-black rule include: atypical network, negative network, irregular streaks, regression structures, and irregular brown structureless areas.

Note: In addition to detecting nodular melanoma, the presence of blue-black color can also aid in detection of other heavily pigmented skin malignancies, including pigmented nodular BCCs.

---

ABCD Rule of Dermoscopy

Purpose: A semi-quantitative scoring system created by Stolz and colleagues (1994) for the evaluation of pigmented lesions. This is a differentiation algorithm (not purely a triage tool).

Criteria and Scoring:

Criterion	Assessment	Points	Multiplication Factor	Score Range
A -- Asymmetry	Contour AND content (color/structure distribution) in two perpendicular axes	0 (none), 1 (mono-axial), 2 (bi-axial)	x 1.3	0 -- 2.6
B -- Border	Abrupt cutoff of pigmentation at perimeter; lesion divided into 8 pie-shaped sections; score 1 for each segment with abrupt cutoff	0 -- 8	x 0.1	0 -- 0.8
C -- Colors	Presence of: white, red, light brown, dark brown, blue-gray, black (1 point each)	1 -- 6	x 0.5	0.5 -- 3.0
D -- Dermoscopic structures	Presence of: pigment network, branched streaks, dots, globules, homogeneous/structureless areas (1 point each). Homogeneous areas include hyperpigmented blotches, hypopigmented areas, depigmented or scar-like areas involving >10% of the lesion surface.	1 -- 5	x 0.5	0.5 -- 2.5

Total Dermoscopy Score (TDS): Sum of all four weighted scores.

TDS	Interpretation
< 4.75	Benign
4.75 -- 5.45	Suspicious
> 5.45	Highly suggestive of malignancy (melanoma)

TDS range: 1.0 -- 8.9 (theoretical: 0.5 -- 8.5 per some sources)

Important note: In contrast to most other algorithms, the ABCD rule of dermoscopy and the CASH algorithm are the only methods that take into account both the contour (shape) and the content (color/structure distribution) of the lesion during asymmetry evaluation.

Performance:

Metric	Range
Sensitivity (pigmented melanoma)	78% -- 98%
Specificity (experts)	45% -- 80%
Specificity (non-experts)	56% -- 78%

---

ABCDE Modification

The ABCDE method is a clinical (not dermoscopic) modification that adds E for Evolution to the original clinical ABCD criteria (Asymmetry, Border irregularity, Color variation, Diameter >6 mm). The E criterion acknowledges that change over time (evolution) is an important indicator of melanoma.

While the delineation of dermoscopic algorithms has certainly improved diagnostic accuracy, the ABCDE method for clinical examination remains a useful adjunct, though it is limited in cases where nevi and melanoma are difficult to distinguish clinically.

Reference: Rigel DS, Friedman RJ, Kopf AW, Polsky D. ABCDE -- an evolving concept in the early detection of melanoma. Arch Dermatol. 2005;141:1032-4.

Check Your Understanding

In the ABCD rule of dermoscopy, what four features are scored and what is the threshold for suspicion?

The ABCD rule scores Asymmetry (0-2), Border irregularity (0-8), Color diversity (1-6 colors), and Dermoscopic structures (1-5 types). Each is multiplied by a weighting factor. A total dermoscopy score (TDS) above 5.45 suggests melanoma, while scores below 4.75 suggest a benign lesion.

---

Menzies Method

Purpose: Developed to differentiate invasive melanomas from other pigmented lesions.

Structure: Evaluates 11 dermoscopic criteria classified into negative features (low sensitivity for melanoma when absent) and positive features (high specificity for melanoma, >85%).

Negative Features (2) -- Neither can be present in melanoma:

Feature	Definition
Symmetrical pigmentation pattern	Symmetric pigment pattern across all axes
Presence of only one color	Only one of: tan, dark brown, black, gray, blue, red

If both negative features are present: the diagnosis of melanoma is excluded.

Positive Features (9) -- At least one must be present to consider melanoma:

#	Feature	Description
1	Blue-white veil	Irregular and confluent blue pigmentation with an overlying white "ground glass" film, not associated with red-blue lacunae
2	Multiple brown dots	Aggregations of dark brown dots, usually within the body of the lesion
3	Pseudopods	Finger-like projections with small knobs at their tips, directly connected to the tumor body or pigment network
4	Radial streaming	Radial and asymmetric linear extensions at the edge of the lesion
5	Scar-like depigmentation	White, irregular area of depigmentation
6	Peripheral black dots/globules	Black dots or globules at or near the edge of the lesion
7	Broadened network	Pigment network with areas of thick grids
8	Multiple blue/gray dots	Diffuse, partly aggregated dots, "pepper-like" in appearance
9	Multiple colors	Presence of five or more colors (of the six: tan, dark brown, black, gray, blue, red)

Decision logic: If both negative features are present AND no positive feature is present, melanoma is excluded. If any positive feature is present, melanoma should be suspected.

Performance:

Metric	Range
Sensitivity (pigmented melanoma)	86% -- 95%
Sensitivity (amelanotic melanoma)	54%
Specificity (experts)	71% -- 78%
Specificity (non-experts)	38% -- 76%
Diagnostic accuracy	83%

---

Seven-Point Checklist

The seven-point checklist evaluates seven dermoscopic features frequently associated with melanoma, categorized into major and minor criteria.

Classic Version (Argenziano et al., 1998)

Major Criteria (2 points each):

Criterion	Definition	Score
Atypical pigment network	Prominent (hyperpigmented or thick) and irregular network	2
Blue-whitish veil	Irregular, structureless white-blue area with an overlying "ground glass" film; cannot occupy the entire lesion	2
Atypical vascular pattern	Linear irregular or dotted vessels, irregularly distributed outside areas of regression	2

Minor Criteria (1 point each):

Criterion	Definition	Score
Irregular streaks	Radial and asymmetric linear or bulbous projections at the edge of the lesion	1
Irregular blotches	Black, brown, and/or gray structureless areas with irregular shape or distribution	1
Irregular dots and globules	Black or brown round structures irregularly distributed	1
Regression structures	White scar-like depigmentation and/or "peppering"	1

Scoring:

• Major criteria range: 0 -- 6 points
• Minor criteria range: 0 -- 4 points
• Total score range: 0 -- 10 points
• Threshold for melanoma: Total score of 3 or more

flowchart TD
 A[Pigmented Lesion] --> B{Major Criteria}
 B --> C[Atypical pigment<br/>network? +2]
 B --> D[Blue-whitish<br/>veil? +2]
 B --> E[Atypical vascular<br/>pattern? +2]
 A --> F{Minor Criteria}
 F --> G[Irregular<br/>streaks? +1]
 F --> H[Irregular<br/>blotches? +1]
 F --> I[Irregular dots<br/>& globules? +1]
 F --> J[Regression<br/>structures? +1]
 C & D & E & G & H & I & J --> K[Total Score<br/>0-10 points]
 K -->|Score >= 3| L[Suspicious for<br/>melanoma -- Biopsy]
 K -->|Score < 3| M[Low suspicion --<br/>Monitor or reassure]

Revised Version (Argenziano et al., 2010)

The revised seven-point checklist lowered the threshold for biopsy:

• Each criterion (major or minor) scores 1 point (all criteria weighted equally)
• Threshold for excision: Total score of 1 or more (i.e., the presence of any single criterion is sufficient to consider a lesion suspicious)
• Result: Higher sensitivity but lower specificity compared to the classic version

The authors acknowledge that a sensitive and specific method requires consideration of additional context: clinical characteristics, age and skin type, lesion location, whether the lesion is an outlier (comparative approach), and whether it has changed during follow-up.

Performance:

Version	Sensitivity	Specificity
Classic (score >= 3)	62% -- 95%	35% -- 97%
Revised (score >= 1)	88%	75%
Amelanotic melanoma (classic)	41%	--

Note on Terminology: The seven-point checklist described here is sometimes referred to as the Italian version (Argenziano et al., 1998). The term "Glasgow 7-point checklist" refers to a clinical (not dermoscopic) scoring system using different criteria (change in size, shape, color; inflammation; crusting/bleeding; sensory change; diameter >=7 mm). This module focuses on the dermoscopic seven-point checklist.

---

CASH Algorithm

Purpose: The CASH (Color, Architecture, Symmetry, Homogeneity) algorithm provides a semi-quantitative scoring system for the dermoscopic evaluation of pigmented lesions.

Criteria and Scoring:

Criterion	Assessment	Score Range
Color	Presence of each: light brown, dark brown, brown, red, white, blue (1 point each)	0 -- 6
Architectural disorder	None/mild (0): colors and structures distributed in an organized or slightly disordered manner; Moderate (1): structures lose uniformity and are distributed irregularly; Marked (2): completely disorganized (chaotic) arrangement	0 -- 2
Symmetry	Taking into account shape AND dermoscopic structures: Bi-axial symmetry (0); Mono-axial symmetry (1); Bi-axial asymmetry (2)	0 -- 2
Homogeneity/Heterogeneity	Number of dermoscopic structures present (1 point each): network, dots/globules, streaks/pseudopods, blue-white veil, regression structures, blotches, polymorphous vessels	0 -- 7

Total CASH score range: 2 -- 17

Threshold: A total score of 8 or more is considered suspicious for melanoma.

Important note: Like the ABCD rule, CASH evaluates both the contour (shape) and the content (structure distribution) for asymmetry assessment.

Performance:

Metric	Range
Sensitivity	87% -- 98%
Specificity	67% -- 68%

---

BRAAFF Rule

Purpose: Created by Lallas et al. (2015) specifically for the evaluation of volar (acral) skin lesions.

Structure: The algorithm uses both positive (associated with melanoma) and negative (associated with benign nevi) criteria, with each criterion having a different score weight based on the strength of its association.

Scoring:

Type	Letter	Criterion	Score
Positive	B	Irregular blotch	+1
Positive	R	Parallel ridge pattern	+3
Positive	A	Asymmetry of structures	+1
Positive	A	Asymmetry of colors	+1
Negative	F	Parallel furrow pattern	-1
Negative	F	Fibrillar pattern	-1

Interpretation: A total score of >= 1 is required for the diagnosis of acral melanoma (i.e., the lesion should be considered suspicious).

Note: The parallel ridge pattern carries the highest positive weight (+3), reflecting its strong association with acral melanoma. The negative criteria (parallel furrow pattern, fibrillar pattern) are characteristic benign acral patterns that reduce suspicion.

---

Clinical Scenario

A 65-year-old man presents for a routine skin check. You evaluate a 10 mm pigmented macule on the left forearm using the Three-Point Checklist. You note: (1) Asymmetry of structures -- the lesion has an irregular reticular pattern on one side and a structureless area on the other (1 point). (2) Blue-white structures -- a faint blue-whitish haze is present centrally (1 point). (3) Atypical network -- thick brown lines with variation in color and spacing are present in the reticular area (1 point). Total score: 3.

What is your diagnosis and key dermoscopic findings?

Melanoma (suspected -- Three-Point Checklist score 3, threshold is 2)

The Three-Point Checklist requires only a score of 2 or more to recommend biopsy or referral. This lesion scores 3/3, indicating high suspicion. The asymmetry of structures reflects a disorganized growth pattern. The blue-white structures suggest either melanin deep in the dermis with overlying orthokeratosis (blue-white veil) or regression. The atypical network indicates irregularly thickened rete ridges with disarranged melanocyte proliferation. This case also illustrates cross-algorithm concordance: applying TADA would flag the disorganized pattern (Step 2), and the ABCD rule would generate a high TDS from asymmetry, border, color, and dermoscopic structure scores.

Prediction without Pigment

This algorithm was created for the evaluation of amelanotic (non-pigmented) lesions and is discussed in detail in Module 05. It is referenced here for completeness as the counterpart to pigmented lesion algorithms.

---

Chaos and Clues

This algorithm is discussed in detail in Module 06. It was developed for the evaluation of pigmented skin lesions with a sensitivity of 90.6% (BCC 98.5%, SCC 86.5%, melanoma 79.3%) and a specificity of 62.7% for malignancy of any type.

---

Key Takeaways

• The 7-point checklist assigns weighted scores to major criteria (atypical network, blue-white veil, atypical vascular pattern) and minor criteria, with a threshold of 3 points.
• No single algorithm is definitively superior; choice depends on clinical setting, user experience, and whether sensitivity or specificity is prioritized.
• All algorithms share common features that predict malignancy: asymmetry, irregular vasculature, blue-white structures, and atypical pigment patterns.

Criterion	3-Point	AC Rule	Blue-Black Rule	Chaos & Clues	Prediction w/o Pigment	TADA
Asymmetry	x	x		x		x
Color variation	x	x	x	x		x
Atypical network	x			x
Blue-white structures	x			x		x
Blue-black colors (>10%)			x			x
Ulceration					x	x
Shiny white structures					x	x
Keratin clues					x	x
Vascular pattern					x	x

---

Key Takeaways

• Algorithm comparison shows that simpler algorithms (3-point, TADA) favor sensitivity while more detailed ones (ABCD, pattern analysis) can achieve higher specificity.
• In primary care or screening settings, high-sensitivity algorithms are preferred to minimize missed melanomas even at the cost of more referrals.
• Experienced dermoscopists may use pattern analysis as the primary method, reserving algorithmic checklists for equivocal cases or teaching.