In this lecture, the following basic steps by which I routinely scan specimens in our hospital will be presented with examples. 1. Evaluate the specimen preparation. 1) Is the incision for the specimen made perpendicular to the skin surface? 2) Is the slice of tissue from volar skin made perpendicular to the furrows of skin? 2. Estimate the specimen size and location. 1) Estimate the size of the lesion from the magnification of the objective lens. 2) Estimate the specimen location. 3. Precaution before evaluation 1) Observe the specimens without clinical information as much as possible. 2) Obtain as much information as possible at low magnification. 4. The steps for observation 1) At low magnification: Check the symmetric properties and circumscription of the lesion based on the following points. a. Distance from the densest area of the lesion to both ends. b. Variation of the thickness of epidermis from the center to both ends. c. Distribution of melanin in the coronoid layer, epidermis, and dermis. d. Distribution of nests and distance between each nest. e. Density of solitary distributed melanocytes. f. Existence of inflammatory infiltration in the dermis and its distribution. g. Continuity of the spread of nests and tumor cells in both ends. h. Is the bottom of the lesion smooth or not? 2) At high magnification: Check the details of tumor cells. a. Tumor cells in the epidermis: Existence of necrosis, atypia (large nucleolus), or mitosis. b. Other findings in the epidermis: Distribution of melanin in the cornified layer, the existence of tumor cells in the upper epidermis, the polymorphism of tumor cells, the relationship between tumor cells and keratinocytes. c. In the dermis: An overlapping, crowded, or sheet-like gathering of tumor cells, maturation of tumor cells, mitotic figures, or melanin of tumor cells at the bottom of the lesion. d. In the adnexal area: The existence of tumor cells in adnexal walls. 5. After provisionally giving a pathological diagnosis, check discrepancies between the pathological diagnosis and clinical findings. Return to the pathological evaluation if necessary.

1. 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

2. Contents
1.Preparation before observation
2.Clues suggesting melanoma
3.Clinical findings to avoid over diagnosis

3. 1. Preparation

4. Preparation 1
Evaluate
specimen

5. Evaluate the specimen (1)
Go!
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).

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

7. 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

8. Preparation 2
Free from
clinical information
This 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.

9. Preparation 3
Start
at low magnification
By Dr. Ackerman

10. 2. Clues suggesting
melanoma

11. 13 findings to be checked

12. 1/13 Size?

13. 5mm 5mm
Caution

14. 2/13
Solitary > Nests?
VS
X

15. Solitary proliferation of melanocytes

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

17. 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

18. 3/13Symmetric?
(1) Distance from the center

19. 3/13Symmetric?
(2) Thickness of epidermis from
the center to both ends

20. 3/13Symmetric?
(3) Distribution of nests & melanocytes

21. Equidistance?
VS

22. (3) Distribution of spaces (melanocytes)
You can see randomly distributed spaces.

23. 3/13Symmetric?
(4) Distribution of melanin in the
cornified layer, epidermis, and dermis

24. In this specimen resected from acral
region, 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.
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.

25. Symmetric?
(4) Distribution of melanin
(melanophage) in epidermis and dermis
VS
X

26. 3/13 Symmetric?
(5) Inflammatory infiltration

27. (5) Inflammatory cells
VS
x

28. 3/13 Symmetric?
(6) Heterogeneity of tumor cells

29. Round Spindle
x

30. 4/13
Circumscription?
Nests & melanocytes

31. 5/13
Melanocytes
in upper epidermis

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

33. 6/13 Size of
Nests & melanocytes

34. Size of nests & melanocytes
VS
x

35. 7/13
Confluent?
In dermis
The distribution of nevus cells is confluent or cluster?

36. Sheet

37. Relationship
Nests, melanocytes ＆ collagen bundles
VS
Spitz Melanoma

38. 8/13
Shape of bottom?

39. Shape of bottom
FLA
VS
Flat
Wedge shaped
X

40. 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.

41. High magnification
10/13 Atypia
11/13 Mitosis
12/13 Necrosis
13/13 Maturation

42. 10 Atypia?
Big and red nucleorus

43. 10 atypia
11 necrosis
12 mitosis
Presence & Distribution
in the bottom of the lesion

44. 13 Maturation

45. 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

46. 3. Clinical findings
to avoid over
diagnosis
Last step

47. Check
clinical
information
Check discrepancies between the pathological
diagnosis and clinical findings. If necessary, return to
the pathological evaluation.

48. Clinical signs
to pay attention
when your diagnosis is
malignant > benign

49. Age
Children
The specimen removed from infants
and children frequently shows
atypical findings, such as remarkable
atypia, necrosis, and mitosis.

50. Location
Mucosa (eyelid, genital)
Nail
Palm & Sole

51. History
of resection
Recurrent nevus after initial
resection shows irregular
findings like melanoma.

52. Halo nevus

53. Spitz nevus

54. If your diagnosis….melanoma?
Check !!
Age
Location
History
Halo
Spitz

55. 1. Check condition of specimen
2. Without clinical information
3. At low magnification

56. If first impression……. Benign?
Check 13 pathological findings
+ dermoscopy
If first impression….. Malignant?
Check 5 clinical findings

57. Thank you