Dermatopathology

What is it dermatopathology?

Dermatopathology is a subspecialty of pathology.

• Pathology is the study of diseases. It includes the study of the causes, course and progression and complications arising from the disease.
• Anatomical pathology, or histopathology, refers to the study of structural and compositional changes that occur in organs and tissues as a result of disease.
• A pathologist is a physician trained in anatomical pathology who examines, describes, and interprets pathologic specimens to arrive at a specific finding or diagnosis.
• Dermatopathology is the study and description of structural and compositional changes that occur in skin diseases.

From a practical point of view, dermatopathology involves microscopic examination, description and interpretation of biopsy samples obtained from the skin. This is usually done by a general pathologist (who may or may not have received specific training in dermatopathology) or a dermatopathologist (a physician specifically trained in dermatopathology, but who may not have fully trained in anatomical pathology). Dermatologists often have clinical training. dermatology.

Interpreting skin samples can be complicated and difficult, as many inflammatory Skin diseases share the same basic inflammatory process or pattern. The final diagnosis requires clinical input and clinicopathological correlation.

How are skin biopsy samples examined?

The skin biopsy samples are processed and then stained with hematoxylin and eosin (H&E). Eosin is acidic in nature and stains the basic / alkaline / acidophilic structures red / pink. Hematoxylin is alkaline and the spots are acidic / basophilic structures (eg deoxynucleic acid, ribonucleic acid inside the cell nuclei) blue. Depending on the observed dermatopathological pattern and / or clinical characteristics, special stains may be requested to identify the agents that cause the condition (eg. bacteria or fungi), specific substances deposited on the skin (eg. amyloidiron or melanin) or specific markers to identify the origin, nature and distribution of cells in the sample being examined.

The specimen is systematically examined by observing the structure of the epidermis, dermis, subcutis, fascia and underlying structures. Based on the findings, the pathologist can reach a definitive diagnosis or list various possible explanations, creating a differential diagnosis. The integration of clinical information along with pathological findings generates the final diagnosis, or lists several possible explanations, creating a differential diagnosis. The integration of clinical information together with pathological findings generates the final diagnosis.

Possible errors in diagnosis.

Pathologists depend on the doctor to provide a good history and differential diagnosis, and their work is easier with a large biopsy sample than with a small one. Even then, the sample may not be representative of the disease as a whole.

• The biopsy may have been removed injury.
• The biopsy may not contain diagnostic material.
• The biopsy can be fragmented or crushed.
• There may be processing errors.
• An incorrect diagnosis may arise due to lack of information on the application form.
• the microscopy It may seem normal despite a fairly obvious clinical illness.
• The changes may be too subtle to diagnose if the injury is too early to develop.
• Dark secondary changes primary pathology. These include excoriation, ulcerationhealing infection, necrosis and fibrosis.
• The thin section examined by the pathologist may not contain any part of the lesion present in another portion of the original sample. In this case, a less The biopsy sample could have led to the diagnosis.
• Dense cellular infiltration it can obscure the presence of another pathological characteristic, avoiding its identification.
• Two very different skin conditions can look similar under a microscope.

Common inflammatory skin diseases.

Histological patterns of eczema, psoriasis, lichen planus, bullous pemphigoid, vasculitis and granuloma override are described below.

Eczema/dermatitis

The histological characteristics of eczema are:

• Spongiosis in acute eczema with associate lymphocyte exocytosis
• Acanthosis in chronic eczema
• Parakeratosis and perivascular lymphohistiocytic infiltrate
• Excoriation and signs of rubbing (irregular acanthosis and perpendicular orientation of collagen in dermal papillae) in chronic cases (lichen simplex).

Psoriasis

Chronic typical pathological features license plate psoriasis are:

• Hyperkeratosis - mainly parakeratosis, some orthokeratosis
• Neutrophils in stratum corneum and scaly cell layer
• Hypogranulosis
• The epidermis is thin on the dermal papillae.
• Regular acanthosis, often clubbed challenge ridges
• Relatively little spongiosis
• Expanded capillaries in dermal papillae
• Perivascular lymphohistiocytic infiltrate.

Lichen planus

The histological characteristics of lichen planus are:

• Orthokeratosis
• Hypergranulosis
• Irregular acanthosis with saw teeth ridge crests (major injuries)
• Colloid bodies in the lower epidermis and upper dermis
• Liquefaction degeneration of the basal cap
• Lichenoid lymphohistiocytic infiltrate in the upper dermis (interface dermatitis) and sometimes inside the epidermis
• Melanin incontinence.

Bullous pemphigoid

The histological characteristics of bullous pemphigoid are:

• Subepidermal ampoule
• Viable ceiling over new ampoule, necrotic over an old blister
• Variable perivascular infiltrate (lymphocytes, histiocytes, eosinophils)
• Pre-blistering lesions may show spongiosis with eosinophils exocytosis (eosinophilic spongiosis).

Vasculitis

Note: vascular Damage may be a secondary feature of conditions that are not primarily vasculitis.

The histological characteristics of leukocytoclastic vasculitis (small vessel) are:

• Damage to the vessel wall - necrosis, hyalinization, fibrin
• Invasion of inflammatory cells in the vessel walls.
• Red blood cells extravasation
• Nuclear neutrophil leukocytoclasia powder
• Severe cases can show ischemic necrosis of the epidermis.

Granuloma annulare

The histological characteristics of the granuloma annulare are:

• Normal epidermis
• Central foci of dermal collagen degeneration (necrobiosis) and mucin accumulation
• Histiocyte palisade
• Multinucleate giant cells
• A single presentation of inflammatory cells between bundles of collagen ("occupied" dermis).

Common cutaneous tumors

• Histology of common skin tumors seborrheic keratosisbasal cell carcinomaSquamous cell carcinoma in the place (intraepidermal carcinoma), squamous cell carcinoma, cysts, lentigo, melanocytic nevus, melanoma and dermatofibroma are described below.

Seborrheic keratosis

The histological features of seborrheic keratosis can be quite varied and may overlap with solar lentigo, but generally show:

• Hyperkeratosis papillomatosisacanthosis
• Basaloid keratinocytes
• horn cysts
• Abundant melanin in the basal layer or in the entire epidermis
• Acute demarcation base of epidermal hyperplasia
• Located largely on the surrounding epidermis

Irritated seborrheic keratosis can show many suggestive features of malignancy, and can sometimes be difficult to differentiate from squamous cell carcinoma.

Basal cell carcinoma

The histological features of basal cell carcinoma are typically:

• Cohesive basaloid nests tumor cells (sometimes with a small amount of squamous differentiation)
• Peripheral palisade of nuclei at the margins of cell nests
• Retraction artifact (clefts) around cell nests
• Variable inflammatory infiltrate and ulceration.

Actinic keratosis

The histological characteristics of actinic keratosis are:

• Hyperkeratosis and / or ulceration.
• Parakeratosis columns, overlying. atypical keratinocytes, separated by areas of orthokeratosis
• Basal atypical keratinocytes with varying degrees of overlying maturation loss, hyperchromatism, pleomorphism, increased and abnormal mitosis, dyskeratosis - the complete thickness change can be called “bowenoid actinic keratosis”
• Chronic perivascular inflammatory infiltrate or variable superficial lichenoid
• Solar elastosis.

Squamous cell carcinoma in situ

The histological characteristics of SCC in situ (intraepidermal carcinoma) show a wide overlap with actinic keratosis and are:

• Hyperkeratosis, parakeratosis
• Acanthosis
• Full thickness epidermal involvement by atypical keratinocytes, with paleness vacuolated or multinucleated cells
• In some injuries pagetoid spread on the margins.

Invader squamous cell carcinoma

The histological characteristics of invasive squamous cell carcinomas can vary, but generally they are:

• Proliferation of atypical keratinocytes
• Dermis invasion
• Variable degrees of keratinizationsometimes scaly eddies or curb pearls

Epidermoids and pillar cysts

The histological characteristics of epidermal inclusion cysts (epidermoid cysts) are:

• Cyst lined by scaly epitheliumsometimes flattened with a granular layer
• Keratin laminated inside the cyst

Dermoid cysts differ by showing hair follicles and sebaceous glands on the wall and hairs on the contents

• Milia they are very small epidermoid cysts

Tricylemmal cysts (abutments) show:

• Scaly lining but without granular layer.
• Dense keratin content
• Frequent calcification.

Lentigo

The histological characteristics of lentigines They are:

• Hyperpigmented elongated ridge ridges
• Increased melanocytes.

Melanocytic nevus

The histological characteristics of the melanocytic. naevi They are:

• Variable epidermal changes: atrophy, hyperplasia, papillomatosis, tube cysts
• Melanocyte nests / nevus cells at the dermoepidermal junction (junction nevi) and / or in the dermis (compound nevus, dermal nevus)
• Naevus cells in the epidermis confined to the basal layer, generally at the tips of the rete ridges
• Round nevus cells generally show a decreasing size of both cells and cell nests with increasing depth in the dermis (so-called maturation)
• Little inflammation unless you are traumatized (except halo and dysplastic naevi).

Melanoma

The histological characteristics of melanoma differ, depending on the type of tumor, but in general terms they show:

• Asymmetric melanocyte proliferation
• Atypical melanocytes that invade up through the epidermis and down into the dermis
• Cytological variable atypia: loss of maturation, pleomorphism, hyperchromatism, increased mitosis, prominent nucleoli.

Dermatofibroma

The histological characteristics of the dermatofibroma are:

• Epidermal hyperplasia (sometimes mimicking basal cell carcinoma)
• Hyperpigmented basal layer
• Circumscribed but bad demarcated spindle proliferation fibroblasts
• Histiocytes and few giant cells.
• Variable amounts of collagen.