From dermoscopedia
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Definition: no basic elements, too few to constitute a pattern, or the visible structures cannot be assigned to one of the five basic elements.

Lesions that only have a structureless pattern are difficult to diagnose using dermatoscopy and often require histopathology.

One color predominates over all others

  • Black + structureless: presence of hemoglobin (not melanin) and its degradation products, e.g. hemorrhagic crusts, hemorrhages in the epidermis and thrombosed vessels.
  • Differential diagnoses: heavily pigmented melanocytic lesions, e.g. Reed nevus, Clark nevus or melanoma.
  • Blue + structureless: "blue nevi" of all types.
  • Differential diagnoses: melanomas melanoma metastases, structureless blue pigmented basal cell carcinomas.
  • Brown + structureless: solar lentigo, flat seborrheic keratosis, pigmented Bowen’s disease, melanocytic nevus of "superficial" or "superficial and deep" congenital type.
  • Red + structureless: recent hemorrhage in the stratum corneum. This will become a black structureless lesion as the hemoglobin degrades, before it entirely disappears due to transepidermal elimination.

More than one color

Difficult to decide whether clods or structureless. Clods: well circumscribed and always occur in numbers. Structureless: one large contiguous area.

  • Colors of keratin (yellow and orange): keratinizing lesions such as seborrheic keratosis.
  • Differential diagnoses: basal cell carcinoma
  • Colors of hemoglobin (red and purple): hemorrhage, or hemorrhage in a pre-existing lesion such as a nevus.
  • Black zones in structureless lesion: thrombosis.
  • Differential diagnoses: black should be attributed to blood when it appears together with red or purple and attributed to melanin when it appears together with brown, blue or gray.
  • Symmetrical distribution of melanin: nevus.
  • Asymmetrical distribution of melanin: melanoma, melanoma metastasis, seborrheic keratosis.
  • Differential diagnosis: pigmented basal cell carcinoma or a dermatofibroma.
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