Pathological evaluation of melanocytic lesions
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Pathological evaluation of melanocytic lesions Hisashi Uhara, MD. Associate professor Department of Dermatology, Shinshu University School of Medicine Asahi 3-1-1, Matsumoto, Japan [email protected]
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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.
Transcript of Pathological evaluation of melanocytic lesions
Pathological evaluation of
melanocytic lesions
Hisashi Uhara, MD.
Associate professor
Department of Dermatology,
Shinshu University School of Medicine
Asahi 3-1-1, Matsumoto, Japan
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
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