A 60-year-old man consulted for this black-blue tumor on his back.

Patient did not know when this lesion appeared.

Dermoscopy revealed a homogenous blue pattern with whiter areas.

Two diagnosis were suspected:

- blue nevus

- melanoma

This lesion was excised and pathology revealed a blue nevus with fibrous involution

Blue lesion on a leg

A 58-year-old woman consulted for a pigmented lesion on her right leg present for many years.

NB: a scar is due to a former fracture.

Dermoscopy revealed an homogeneous blue pattern in favor of a benign blue nevus.

Blue nodule

A 53-year patient consulted for this enlarging temporal  blue nodule.

Dermoscopy revealed a blue homogeneous pattern and some barely visible arborizing tree vessels in favour of a basal cell carcinoma.

This lesion was excised and pathology confirmed the diagnosis of basal cell carcinoma.

Fig 3: arborizing tree vessels (white arrows)

Homogeneous blue pattern

A 65-year-old man presented 6 blue lesions located on his trunk. Dermoscopy revealed a blue structure-less pattern (homogeneous blue pattern).
This patient had been treated 10 years before for a leukaemia. These blue lesions with blue homogeneous patterns not well demarcated corresponded to radiotherapy tattoos.

Radiotherapy tattoo

Radiotherapy tattoo

The main other cause of blue homogeneous pattern is blue nevus.
Here are above two examples of blue nevi.

Blue nevus

Blue nevus

Blue nevus

Typical blue homogeneous pattern* in favour of a blue nevus.

* synonym: blue structure less pattern

Blue nevus

A 24-year-old man presented a dark blue lesion on her right arm. Pathology revealed a blue nevus.
Dermoscopy revealed a blue pigmentation and an area of brown pigmentation and dots.
Blue nevi do not have systematically a blue homogeneous pattern and in some cases dermoscopy reveal islands of depigmentation or areas of brown pigmentation.

Blue nevus

A 32-year-old woman consulted for this blue lesion on her nose.
Dermoscopy revealed an homogeneous blue pattern in favor of a blue nevus.

Blue nevus

A 34-year-old woman consulted for a dark blue lesion on her left ankle. The lesion was not enlarging for many years.

Dermoscopy revealed a blue homogenous pattern with hypopigmented area.

The lesion was removed and pathology confirmed the diagnosis of blue nevus.