3. BENIGN MELANOCYTIC
TUMORS
Melanocytic tumors may arise from ,
1. Naevus cells – Naevocellular Naevi
2. Epidermal melanocytes – lentigo, freckles,
pigmentation associated with Albright’s
syndrome and café – au – lait spots of
neurofibromatosis.
3. Dermal Melanocytes – Mongolian spots naevi of
Ota, blue naevus.
4. NAEVOCELLULAR NAEVUS
Pigmented naevi or moles are common lesions
on the skin.
They are mostly tan to brown, uniformly
pigmented, small (<6mm across) , solid regions of
relatively flat(macules) to elevated skin (papules)
with well defined rounded border.
6. Other disorders of Pigmentation of
Melanocytes
1. Lentigo – Replacement of the basal layer of the
epidermis by melanocytes.
2. Blue Naevus – Characterized by dendritic
spindle naevus cells rather than the usual
rounded or cuboid naevus cells.
3. Dysplastic Naevi – Certain atypical naevi
which have increased risk of progression to
malignant melanoma. These lesions are larger,
multiple , irregular bordered and slightly
elevated than usual congenital naevi with
variable pigmentation.
8. MALIGNANT MELANOMA
Melanocarcinoma arises from melanocytes
which is spread fast and occurs at all ages.
Etiology – Unknown, but usually considered
due to higher exposure of sunlight.
Melanomas can occur at various sites such as
oral and anogenital mucosa, oesophagus,
conjuctiva , orbit and leptominges.
Common sites : Skin and Trunk ( in men) ,
legs ( in women) .
9. Risk factors:
Persistent change in appearance of a mole.
Presence of dysplastic nevi.
Family history of melanoma.
More than 50 moles 2mm or more in diameter.
- Molecular studies in hereditary cases have
revealed germiline mutation in CDKN2A gene
which encodes for cycline-dependent kinase
inhibitor, activating mutations that turn on
telomerase and mutation in several other tumour
suppressor genes.
10. Morphological classification of
cutaneous malignant melanomas.
1. Lentigo Maligna Melanoma – Develops from pre-
existing Lentigo. It is a malignant melanoma in-situ.
Favourable Prognosis.
2. Superficial spreading melanoma – Develops from
a superficial spreading melanoma ( pagetoid
melanoma ) in 5 to 7 years. Slightly elevated lesion.
Unfavorable prognosis.
3. Acral Lentigous Melanoma – Occurs commonly in
soles, palms, and mucosal surfaces.Tumour
undergoes metastasis and ulceration rapidly.
Prognosis is worse.
4. Nodular Melanoma – Appears as an elevated and
deeply pigmented nodule that grows rapidly with
ulceration. This variant carries the worst prognosis.
5. Desmoplastic melanoma – The tumor has a
fibrotic stroma, neural invasion and frequent local
reccurences.
11.
12. Histological characteristics of
malignant melanoma.
1. Origin – Epidermo-dermal junctional origin.
2. Tumour cells – Larger than naevus cells. May be
epithelioid or spindle shaped. Have amphophillic
cytoplasm and large pleomorphic nuclei. Mitosis is
present. Presence of multinucleated giant cells. The
tumour cells are arranged in various patterns –
masses, sheets, islands, alveoli etc.
3. Melanin – If present ( melanotic) ; If absent (
amelanotic melanoma) without any prognostic
influence. Sometimes there may be no evidence of
melanin granules in the cytoplasm of tumour cells
when stained with H and E. But Fontanna – Masson
stain or dopa reaction reveals melanin granules in the
cytoplasm of tumour cells.
4. Inflammatory Infiltrate – Some amount of
inflammatory infiltrate is present in the invasive
melanomas.
14. Prognosis:
In order to determine the prognosis
of a malignant melanoma, tumour
thickness is measured by its depth
of invasion into the skin.
This is assessed by two types of
staging scales: Clark staging and
Breslow staging.
15. Clark's level is a staging system, used in conjunction with Breslow's
depth, which describes the level of anatomical invasion of the melanoma in
the skin. It was developed by Wallace H. Clark Jr at Harvard University
and Massachusetts General Hospital in the 1960s.
Clark’s Staging Breslow Staging.
Five anatomical levels are
recognized, and higher
levels have worsening
prognostic implications.
These levels are:
Level 1: Melanoma confined
to the epidermis (melanoma
in situ).
Level 2: Invasion into
the papillary dermis.
Level 3: Invasion to the
junction of
the papillary and reticular
dermis.
Level 4: Invasion into
the reticular dermis.
Level 5: Invasion into the
T1:< 1.00mm thickness
T2: 1.01 to 2.00mm
thickness
T3: 2.01 to 4.00mm
thickness
T4: >4.00mm thickness
16.
17. References:
1. Harsh Mohan’s textbook of Pathology
2. Robbins and Contran Pathological Basis of
Disease
3. Wikipedia
4. Cancerresearchuk.com
