Excoriation Traumatic lesion breaking the epidermis
and causing a raw linear area (i.e., deep
scratch); often self-induced
Lichenification Thickened and rough skin characterized by
prominent skin markings (as lichen on a
tree trunk); usually the result of repeated
Macule Circumscribed lesion, 5 mm or smaller in
diameter, characterized by flatness and
distinguished by coloration (patch is
greater than 5 mm)
Onycholysis Separation of nail plate from nail bed
Papule Elevated dome-shaped or flat-topped lesion
5 mm or less across (nodule is greater than
Plaque Elevated flat-topped lesion, usually greater
than 5 mm across (may be caused by
Pustule Discrete, pus-filled, raised lesion
Scale Dry, horny, plate like excrescence; usually
the result of imperfect cornification
Vesicle Fluid-filled raised lesion 5 mm or less
across (Bulla is greater than 5
mm. Blister is the common term for either.)
Wheal Itchy, transient, elevated lesion with
Acantholysis Loss of intercellular cohesion between
Acanthosis Diffuse epidermal hyperplasia
Dyskeratosis Abnormal, premature keratinization within cells
below the stratum granulosum
Erosion Discontinuity of the skin showing incomplete
loss of the epidermis
Exocytosis Infiltration of the epidermis by inflammatory
Intracellular edema of keratinocytes, often seen
in viral infections
Hypergranulosis Hyperplasia of the stratum granulosum, often
Lentiginous A linear pattern of melanocyte proliferation within the
epidermal basal cell layer
Papillomatosis Surface elevation caused by hyperplasia and
enlargement of contiguous dermal papillae
Para keratosis Keratinization with retained nuclei in the stratum
corneum. On mucous membranes, Para keratosis is
Spongiosis Intercellular edema of the epidermis
Ulceration Discontinuity of the skin showing complete loss of
the epidermis revealing dermis or sub cutis
Vacuolization Formation of vacuoles within or adjacent to cells;
often refers to basal cell-basement membrane zone
• Squamous epithelial cells (keratinocytes), in
addition to producing protective keratin
protein, are major sites for the biosynthesis of
soluble molecules (cytokines) that regulate
adjacent epidermal cells as well as cells in the
• Melanocytes within the epidermis are cells
responsible for the production of melanin, a
brown pigment that protects against
potentially injurious ultraviolet (UV) radiation
• Dendritic cells. Skin is constantly battered with
microbial and nonmicrobial antigens that are
Deep dermal and
Blue nevus Non-nested
cells with pink-
Halo nevus Lymphocytic
Melanocytic nevus, junctional type.
A, In clinical appearance, lesions are small, relatively flat, symmetric,
B, On histologic examination, junctional nevi are characterized by
rounded nests of nevus cells originating at the tips of rete ridges
along the dermoepidermal junction.
Melanocytic nevus, compound type.
(A) is more raised and dome-shaped. The symmetry and uniform
pigment distribution suggest a benign process.
(B), compound nevi combine the features of junctional nevi
(intraepidermal nevus cell nests) with nests and cords of nevus cells in
the underlying dermis).
• Dysplastic nevus.
• A, Numerous clinically atypical nevi on the back.
• B, One such lesion (inset A) has a compound
nevus component (left side of scanning field) and
an asymmetric junctional nevus component (right
side of scanning field).
• The former correlates grossly with the more
pigmented and raised central zone and the latter
with the less pigmented, flat peripheral rim.
• C, An important feature is the presence of
cytologic atypia (irregularly shaped, dark-staining
nuclei). The dermis underlying the atypical cells
characteristically shows linear, or lamellar,
• Potential steps of tumour progression in
• A, Lentiginous melanocytic hyperplasia.
• B, Lentiginous junctional nevus.
• C, Lentiginous compound nevus with abnormal
architectural and cytologic features (dysplastic
• D, Early melanoma, or melanoma in radial growth
phase (large dark cells in epidermis).
• E, Advanced melanoma (vertical growth phase)
with malignant spread into the dermis and vessels.
• The risk of malignant transformation of any single
• Clinical and pathologic features are used to gauge the
probability of metastatic spread and prognosis.
• 1) Tumour Depth (The Breslow Thickness)
• (2) Number Of Mitoses;
• (3) Evidence Of Tumour Regression (Presumably Due To
The Host Immune Response);
• (4) The Presence And Number Of Tumour Infiltrating
• (5) Gender; And
(6) Location (Central Body Or Extremity).
• In a retrospective multivariate study by the American Joint
Committee on Cancer (AJCC), tumour thickness and presence
or absence of ulceration had prognostic significance.
• Because most melanomas initially metastasize to regional
Benign Epithelial Tumours
• Benign epithelial neoplasms are common and
usually biologically inconsequential, although they
may cause significant psychological discomfort for
the affected individual.
• These tumours, derived from the keratinizing
stratified squamous epithelium of the epidermis
and hair follicles and the ductular epithelium of
cutaneous glands, often recapitulate the structures
from which they arise.
• They are sometimes confused clinically with
malignancy, particularly when they are pigmented
or inflamed, and histologic examination of a biopsy
• A well-demarcated coin like pigmented lesion
containing dark keratin-filled surface
plugs (inset) is composed histologically of benign
basaloid cells associated with prominent keratin-
filled "horn" cysts, some of which communicate
with the surface (pseudo-horn cysts).
• On histologic examination, these neoplasms are
exophytic and sharply demarcated from the
• They are composed of sheets of small cells that
most resemble basal cells of the normal
• Variable melanin pigmentation is present within
these basaloid cells, accounting for the brown
• Exuberant keratin production (hyperkeratosis)
occurs at the surface, and small keratin-filled
cysts (horn cysts) and invaginations of keratin
into the main mass (invagination cysts) are
• Acanthosis nigricans is a condition marked by thickened, hyper
pigmented skin with a "velvet-like" texture that most
commonly appears in the flexural areas (axillae, skin folds of
the neck, groin, and anogenital regions).
• It can be an important cutaneous marker of benign and
malignant conditions and, accordingly, is divided into two
• The benign type, which constitutes about 80% of all cases,
develops gradually and usually occurs in childhood or during
• It may occur (1) as an autosomal dominant trait with variable
penetrance, (2) in association with obesity or endocrine
abnormalities (particularly with pituitary or pineal tumors and
diabetes), and (3) as part of several rare congenital syndromes
Fibro epithelial Polyp (skin tag)
• The fibro epithelial polyp has many names (acrochordon,
squamous papilloma, skin tag) and is one of the most
common cutaneous lesions.
• It is generally detected as an incidental finding in middle-aged
and older individuals on the neck, trunk, face, and
intertriginous areas as a soft, flesh- coloured, bag-like tumour
often attached to the surrounding skin by a slender stalk
• Epithelial cysts are divided into several
• The epidermal inclusion cyst has a wall
resembling normal epidermis and is filled with
laminated strands of keratin.
• Pilar or trichilemmal cysts have a wall that
resembles follicular epithelium, without a
granular cell layer and filled by a more
homogeneous mixture of keratin and lipid.
• The dermoid cyst is similar to the epidermal
inclusion cyst, but also contains multiple
appendages (such as small hair follicles)
budding outward from its wall.
• The cylindroma is composed of islands of cells
resembling those of the normal epidermal or
adnexal basal cell layer (basaloid cells).
• These islands fit together like pieces of a jigsaw
puzzle within a fibrous dermal matrix .
• Trichoepithelioma is a proliferation of basaloid
cells that forms primitive structures resembling
hair follicles .
• Sebaceous adenoma shows a lobular proliferation
of sebocytes with increased peripheral basaloid
cells and more mature sebocytes in the central
portion, characterized by frothy or bubbly
cytoplasm due to lipid vesicle content (Fig. 25-
• Pilomatrixomas are composed of basaloid cells
that show trichilemmal or hair like differentiation
similar to that seen in the germinal portion of the
normal hair bulb in the anagen growth phase (Fig.
• Apocrine carcinoma shows ductal differentiation
with prominent decapitation secretion similar to
• Actinic keratosis are usually less than 1 cm in diameter; are
tan-brown, red, or skin-colored; and have a rough,
sandpaper-like consistency. Some lesions may produce so
much keratin that a "cutaneous horn" develops.
• A, Excessive scale formation in this lesion has
produced a "cutaneous horn."
• B, Basal cell layer atypia (dysplasia) is associated
with marked hyperkeratosis and Para keratosis.
• C, Progression to full-thickness nuclear atypia,
with or without the presence of superficial
epidermal maturation, heralds the development
of squamous cell carcinoma in situ.
• ACTINIC (Solar) KERATOSIS, i.e. precursor to SCC
• SQUAMOUS CELL CARCINOMA, squamous
“pearls”, intercellular bridges
• BASAL CELL CARCINOMA, by far, MOST
COMMON, BLUE palisading nests
• MERKEL CELL CARCINOMA (TUMOR), VERY
MALIGNANT AND LETHAL, LOOK LIKE SMALL CELL
CA. OF LUNG
• BOTH SCC and BCC related to SUN (i.e., radiation)
• SCC also related to As, carcinogens, chaw, betel
nut, HPV, familial, etc.
• BOTH SCC and BCC can do local damage but very
• MERKEL CELL tumors metastasize early and
extensively, like melanomas.
SQUAMOUS CELL CARCINOMA
• Squamous cell carcinoma is the second most common tumour
arising on sun-exposed sites in older people, exceeded only
by basal cell carcinoma.
• Except for lesions on the lower legs, these tumours have a
higher incidence in men than in women.
• Invasive squamous cell carcinomas are usually discovered
while they are small and resectable.
• Less than 5% of these tumours metastasize to regional nodes;
these lesions are generally deeply invasive and involve the
• A.Lesions are often nodular and ulcerated as
seen in this scalp tumour.
• B, Tongues of atypical squamous epithelium
have transgressed the basement membrane,
invading deeply into the dermis.
• C, A magnified image reveals invasive
tumour cells showing enlarged nuclei with
angulated contours and prominent nucleoli.
• Squamous cell carcinomas that have not
invaded through the basement membrane of
the dermoepidermal junction (termed in situ
carcinoma) appear as sharply defined, red,
• More advanced, invasive lesions are nodular,
show variable keratin production
(appreciated grossly as hyperkeratosis scale),
and may ulcerate .
• The most important cause of cutaneous squamous
cell carcinoma is DNA damage induced by
exposure to UV light.
• Tumour incidence is proportional to the degree of
lifetime sun exposure.
• A second common association is with
immunosuppression, most notably chronic
immunosuppression as a result of chemotherapy
or organ transplantation.
• Immunosuppression may contribute to
carcinogenesis by reducing host surveillance and
increasing the susceptibility of keratinocytes to
infection and transformation by oncogenic
• Other risk factors for squamous cell carcinoma
include industrial carcinogens (tars and oils),
chronic ulcers and draining osteomyelitis, old
burn scars, ingestion of arsenicals, ionizing
radiation, and (in the oral cavity) tobacco and
betel nut chewing .
• Basal cell carcinoma is the most common invasive
cancer in humans, with nearly 1 million estimated
cases per year .
• These are slow-growing tumours that rarely
metastasize. They have a tendency to occur at
sun-exposed sites and in lightly pigmented people.
• As with squamous cell carcinoma, the incidence of
basal cell carcinoma rises sharply with
immunosuppression and in people with inherited
defects in DNA repair such as xeroderma
Basal cell carcinoma. Pearly, telangiectatic nodules (A) are composed
of nests of uniformly atypical basaloid cells within the dermis (B) that
are often separated from the adjacent stroma by thin clefts (C), an
artefact of sectioning.
• the tumour cells resemble those in the normal basal cell layer of
the epidermis. They arise from the epidermis or follicular
epithelium and do not occur on mucosal surfaces. Two patterns are
• Multifocal growths originating from the epidermis and sometimes
extending over several square centimeters or more of skin surface
(multifocal superficial type) and nodular lesions growing downward
deeply into the dermis as cords and islands of variably basophilic
cells with hyper chromatic nuclei, embedded in a mucinous matrix,
and often surrounded by many fibroblasts and lymphocytes.
• The cells at the periphery of the tumour cell islands tend to be
arranged radially with their long axes in parallel
alignment (palisading). In sections, the stroma retracts away from
• Benign fibrous histiocytoma refers to a
heterogeneous family of morphologically and
histogenetically related benign dermal
neoplasms of uncertain lineage.
• These tumours are usually seen in adults and
often occur on the legs of young to middle-aged
• The most common form of fibrous histiocytoma is
referred to as a dermatofibroma.
• These tumours are formed by benign, spindle-
shaped cells arranged in a well-defined,
nonencapsulated mass within the mid-dermis.
• Extension of these cells into the subcutaneous fat
is sometimes observed.
• Many cases demonstrate a peculiar form of
overlying epidermal hyperplasia, characterized by
downward elongation of hyper pigmented rete
ridges (a pseudo- epitheliomatous pattern).
• Dermatofibrosarcoma protuberans is best
regarded as a well-differentiated, primary fibro
sarcoma of the skin.
• These tumours are slow growing, and although
they are locally aggressive and can recur, they
• Clinically they are firm, solid nodules that arise
most frequently on the trunk. They often develop
as aggregated "protuberant" tumours within a
firm (indurated) plaque or nodule that may
Benign fibrous histiocytoma (dermatofibroma). This firm, tan papule
on the leg (A) shows a localized proliferation of benign-appearing
spindle cells within the dermis (B). C, Note the characteristic
overlying epidermal hyperplasia and the tendency of fibroblasts to
surround individual collagen bundles.
• These neoplasms are cellular, composed of
fibroblasts arranged radially, reminiscent of
blades of a pinwheel, a pattern referred to
• Mitoses are rare. In contrast to that in
dermatofibroma, the overlying epidermis is
• Deep extension from the dermis into
subcutaneous fat, producing a characteristic
"honeycomb" pattern, is frequently present .
• These tumours may extend down fibrous septae
in the subcutis and thus require wider excision
• Cutaneous T cell lymphoma (CTCL) represents a
spectrum of lymph proliferative disorders
affecting the skin
• Two different clinical types of malignant T-cell
disorders were originally recognized: mycosis
fungoides, a chronic proliferative process; and a
more aggressive nodular eruptive variant, mycosis
• It is now known that a variety of presentations of
T-cell lymphoma occur in the skin, but this section
will focus on mycosis fungoides.
A, Several ill-defined, erythematous, often scaling, and occasionally
B, Microscopically, there is an infiltrate of atypical lymphocytes that
show a tendency to accumulate beneath the epidermal layer and to
invade the epidermis.
• The histologic hallmark of CTCL of the mycosis
fungoides type is the presence of the Sézary-
• These are T-helper cells (CD4+) that
characteristically form band-like aggregates
within the superficial dermis (Fig. 25-19B) and
invade the epidermis as single cells and small
clusters (Pautrier micro abscesses).
• The term mastocytosis refers to a spectrum of rare
disorders characterized by increased numbers of
mast cells in the skin and, in some instances, in
• A localized cutaneous form of the disease that
affects predominantly children and accounts for
more than 50% of all cases is termed urticaria
• These lesions are multiple, although solitary
mastocytomas may also occur, usually shortly after
A, Solitary mastocytoma in a 1-year-old child. B, By routine histology, numerous
ovoid cells with uniform, centrally located nuclei are observed in the
dermis. C, Giemsa staining reveals purple, "metachromatic" granules within the
cytoplasm of the cells.
• The histologic picture in urticaria pigmentosa or
solitary mastocytoma varies from a subtle
increase in the numbers of spindle-shaped and
stellate mast cells around superficial dermal blood
vessels, to large numbers of tightly packed, round
to oval mast cells in the upper to mid-dermis
• Variable fibrosis, edema, and small numbers of
eosinophils may also be present.
• Mast cells may be difficult to differentiate from
lymphocytes in routine, hematoxylin and eosin-
stained sections, and special metachromatic stains