Pathological evaluation of

melanocytic lesions

Hisashi Uhara, MD.

Associate professor

Department of Dermatology,

Shinshu University School of Medicine

Asahi 3-1-1, Matsumoto, Japan

uhara@shinshu-u.ac.jp

Contents

1.Preparation before observation2.Clues suggesting melanoma3.Clinical findings to avoid over diagnosis

1. Preparation

Preparation 1

Evaluate

specimen

Go!

Evaluate the specimen (1)

If the specimen is made perpendicular to the skin surface.(This is a good specimen because the width of epidermis is entirely same and it is arrayed parallel).

Stop!In These bad specimens, nests or melanocytes are frequently seen in the upper part of the epidermis

Go!

Stop!

Evaluate the specimen (2)

The slice should be made perpendicular to the furrows of skin, especially important in lesions of palm or sole. In the section like this, solitary and irregular proliferation are frequently seen even if it was originally a common nevus with regular nests

Preparation 2

Free from

clinical informationThis way has 2 benefits. One is that we can avoid a bias affected by a clinical information. The other is that it may become good training for us to get a pathological skill.

Preparation 3

Start

at low magnificationBy Dr. Ackerman

2. Clues suggesting melanoma

13 findings to be checked

1/13 Size?

5mm 5mm

Caution

Solitary > Nests?

2/13

VS

X

Solitary proliferation of melanocytes

SpaceIn low magnification, multiple small and irregular spaces may be clue to showing solitary proliferation.

3/13 Symmetric?

(1) Distance from the center

(2) Condition of epidermis

(3) Distribution of nests

(4) Distribution of melanin

(5) Distribution of inflammation

(6) Heterogeneity of tumor cells

3/13Symmetric?(1) Distance from the center

3/13Symmetric?(2) Thickness of epidermis from

the center to both ends

3/13Symmetric?(3) Distribution of nests & melanocytes

Equidistance?

VS

(3) Distribution of spaces (melanocytes)

You can see randomly distributed spaces.

3/13Symmetric?(4) Distribution of melanin in the

cornified layer, epidermis, and dermis

Saida T, Koga H, Goto Y, Uhara H. Characteristic distribution of melanin columns in the cornified layer of

acquired acral nevus: an important clue for histopathologic differentiation from early acral melanoma. Am J

Dermatopathol 2011 Jul;33(5):468-73.

In this specimen resected from acralregion, you can see nests in the basal layer not only under the surface furrow but also under the surface ridge. Ridge dominant proliferation of melanocytes or melanin deposition show clinically parallel ridge pattern, suggesting melanoma. But, in melanin stained section, melanin columns are only seen under the furrows but not ridges. So, this is benign nevus.

VS

Symmetric?

(4) Distribution of melanin

(melanophage) in epidermis and dermis

X

3/13 Symmetric?(5) Inflammatory infiltration

(5) Inflammatory cells

VS

x

3/13 Symmetric?(6) Heterogeneity of tumor cells

Round Spindle

x

4/13

Circumscription?Nests & melanocytes

5/13

Melanocytes in upper epidermis

“ascent” or “casting off” is bad sign.

6/13 Size ofNests & melanocytes

VS

Size of nests & melanocytes

x

7/13

Confluent?In dermis

The distribution of nevus cells is confluent or cluster?

Sheet

Relationship

Nests, melanocytes ＆ collagen bundles

VS

MelanomaSpitz

8/13

Shape of bottom?

FLA

Shape of bottom

VS

Flat

Wedge shaped

X

9/13 Melanocytes in adnexal walls

Melanocytes in adnexal walls are also seen in benign lesions such as congenital nevus. But, if you find solitary proliferation of melanocytes in lower potion of adnexa, it is finding to be cared.

High magnification

10/13 Atypia

11/13 Mitosis

12/13 Necrosis

13/13 Maturation

10 Atypia?

Big and red nucleorus

10 atypia

11 necrosis

12 mitosis

Presence & Distributionin the bottom of the lesion

13 Maturation

Easilear obtainable findings

1 Size (>5mm)

2 Solitary proliferation

3 Symmetry (epidermis, melanin, lymphocytes)

4 Circumscription

5 Melanocytes in upper epidermis

6 Size of nests

7 Confluent

8 Shape of bottom

9 Melanocytes in adnexal walls

10 Atypia

11 Mitosis

12 Necrosis

13 Maturation

3. Clinical findings to avoid over

diagnosis

Last step

Check

clinical

informationCheck discrepancies between the pathological

diagnosis and clinical findings. If necessary, return to

the pathological evaluation.

Clinical signsto pay attention

when your diagnosis is

malignant > benign

Age

Children

The specimen removed from infants

and children frequently shows

atypical findings, such as remarkable

atypia, necrosis, and mitosis.

Location

Mucosa (eyelid, genital)

Nail

Palm & Sole

History

of resection

Recurrent nevus after initial

resection shows irregular

findings like melanoma.

Halo nevus

Spitz nevus

If your diagnosis….melanoma?

Check !!

Age

Location

History

Halo

Spitz

1. Check condition of specimen

2. Without clinical information

3. At low magnification

If first impression……. Benign?

Check 13 pathological findings

+ dermoscopy

If first impression….. Malignant?

Check 5 clinical findings

Thank you