Safety rules — the parallel checks

The TADA three-step sequence is your primary framework, but it doesn't work alone. Four safety rules run in parallel, acting as a safety net for the cases that might slip through the algorithm's structure.

These are the same rules you learned in Module 3. Here's how they integrate with TADA in practice.

The Blue-Black Rule

Any nodular lesion with blue-black colour warrants urgent evaluation — regardless of other features.

This rule can override the normal TADA sequence entirely. You don't need to work through Steps 1, 2, and 3 methodically if a dome-shaped nodule presents with striking blue-black colour. The colour pattern alone is sufficient to trigger urgent further evaluation.

Why a separate rule? Because nodular melanoma can present as a featureless dark nodule that doesn't obviously fit the "disorganised" pattern at Step 2 — it may look uniform in its darkness. The Blue-Black Rule catches this.

Prediction Without Pigment

A changing, growing, or symptomatic amelanotic lesion warrants evaluation — even without pigmented features.

Amelanotic lesions are TADA's blind spot. The algorithm is built around pigmented features — network patterns, colour distribution, pigment depth. When a lesion has no pigment, many of these criteria simply don't apply.

Instead, look for vascular patterns (dotted vessels, polymorphous vessels) and shiny white structures. And crucially, listen to the history: a pink lesion that's growing, changing, or symptomatic should not be dismissed just because TADA can't find pigmented features to analyse.

The Ugly Duckling Sign

A lesion that stands out from the patient's other moles warrants closer evaluation — even if it doesn't trigger specific TADA concerns.

This is a comparative check, not a feature-based one. Step back and look at the patient's mole landscape. Most people's naevi share a family resemblance — similar size, colour, and pattern. An outlier — the one mole that looks different from all the others — deserves a lower threshold for further evaluation, even if its individual features don't seem alarming.

The Evolution Factor

Patient history of change overrides current dermoscopic appearance.

A lesion that looks reassuring today but has been growing, darkening, changing shape, or developing new features over recent months should not be dismissed based on TADA alone. What the patient tells you about how the lesion has changed can matter more than what you see through the dermatoscope right now.

This is why the Clinical Context module exists alongside this one. TADA addresses observation; the patient narrative addresses everything the dermatoscope cannot see.