24: Skin Flashcards
Mast cells filling the papillary dermis. The inset shows mast cells staining red in Leder stain. What spectrum of diseases involve mast cell proliferation?
Urticaria pigmentosa
Icthyosis vulgaris
Thickened stratum corneum, thin/absent stratum granulosum, rest of epidermis is normal thickness. What disease?
Icthyosis vulgaris
Clumped tonofilaments in keratinocytes of the stratum spinosum makes their cytoplasm relatively clear. In the outer stratum spinosum, the clumped fibrils are further compacted and whorl about the nuclei. These cells separate from each other to produce epidermolysis. What disease is shown?
Epidermolytic hyperkeratosis
Suprabasal cleft (arrows) with a few dyshesive (acantholytic) keratinocytes surmounted by hyperkeratosis and parakeratosis. The cleft is not a vesicle because true vesicles contain inflammatory cells and tissue fluid. Dyskeratosis is present above the cleft. What disease?
Darier disease
Large, confluent, sharply demarcated, erythematous plaques on the trunk
Psoriasis
Microscopic examination of a lesion demonstrates that the rete ridges are uniformly elongated, as are the dermal papillae, giving an interlocking pattern of alternately reversed “clubs.” Suprapapillary thinning and striking parakeratosis cause scales on the surface. What disease?
Psoriasis
The clubbed papillae contain tortuous dilated venules as part of the venulization of capillaries. The papilla to the right has one cross-section of its superficial capillary venule loop, which is normal. The papilla in the center shows numerous cross-sections of its venule, indicating striking tortuosity. What disease?
Psoriasis
Neutrophils migrate into the epidermis, emerging from the venulized capillaries at the tips of the dermal papillae. They migrate to the upper stratum spinosum and stratum corneum (arrows). In some forms of psoriasis, pustules are common clinical lesions. What disease?
Psoriasis
Suprabasal dyshesion leads to an intraepidermal blister containing acantholytic keratinocytes with a row of tombstone cells remaining. What disease?
Pemphigus vulgaris
Direct immunofluorescence examination of perilesional skin reveals IgG antibodies in the intercellular substance of the epidermis, yielding a lace-like pattern outlining the keratinocytes.
Pemphigus vulgaris
Dyshesion in the outer stratum spinosum and stratum granulosum. Dyshesive and dyskeratotic keratinocytes in the stratum granulosum (arrows). What disease?
Pemphigus foliaceus
Multiple tense bullae on an erythematous base and erosions, distributed primarily on the medial thighs and trunk
Bullous pemphigoid
A subepidermal blister has an edematous papillary dermis as its base. The roof of the blister consists of the intact, entire epidermis, including the stratum basalis. Inflammatory cells, fibrin and fluid fill the blister. What disease?
Bullous pemphigoid
Direct immunofluorescence study discloses linear deposition of immunoglobulin G (IgG) (and C3) along the dermal–epidermal junction. Ultrastructurally, these antibodies and complement are present in the lamina lucida.
Bullous pemphigoid
Pruritic, symmetric, grouped vesicles on an erythematous base are seen on the elbows and knees
Dermatitis herpetiformis
Dermal papillary abscesses of neutrophils with vesicle formation at the dermal–epidermal junction are characteristic
Dermatitis herpetiformis
Direct immunofluorescence reveals immunoglobulin A (IgA) deposited in dermal papillae in association with anchoring fibrils and elastic tissue fibers. This is the site of neutrophil infiltration and subepidermal vesicle formation. What disease?
Dermatitis herpetiformis
Steroid-responsive “target” papules, characterized by central bullae with surrounding erythema, appeared after antibiotic therapy
Erythema multiforme
Perivascular and periappendageal lymphocytic inflammation is present in the superficial and deep dermis. A hair follicle plugged with keratin is present near the right edge. What disease?
Lupus erythematosus.
An active lesion shows striking basal vacuolization, with keratinocyte necrosis (arrow) forming a dense eosinophilic body (apoptotic/fibrillary/colloid body) that is surrounded by lymphocytes (satellitosis).
Lupus erythematosus
Basal cell necrosis with resultant basal keratinocytic migration and synthesis of new basement mem- brane zone leads to thickening of the epidermal basement membrane zone (BMZ), as evident in this periodic acid–Schiff (PAS) stain. Notice the vacuoles (arrows) on either side of the BMZ, an indicator of cellular injury.
Lupus erythematosus
Lichen planus
A cell-rich, band-like, lymphocytic infil- trate disrupts the stratum basalis. Unlike lupus erythematosus, there is usually epidermal hyperplasia, hyperkeratosis and wedge-like hyper- granulosis
Lichen planus
Hypergranulosis and loss of rete ridges are noted. The site of pathologic injury is at the dermal-epidermal junction where there is a striking infiltrate of lymphocytes, many of which surround apoptotic ker- atinocytes (arrows)
Lichen planus
Palpable purpuric tender papules on the legs of a 25-year-old woman. The condition resolved after therapy for streptococcal pharyngitis. B. The vessel is surrounded by pink fibrin and neutrophils, many of which have disintegrated (leukocytoclasis). Extravasated red blood cells (arrows) and inflammation give the clas- sic clinical appearance of “palpable purpura.”
Cutaneous necrotizing vasculitis
esicles and bullae developed on the volar forearm after application of perfume
Allergic contact dermatitis
Epidermal spongiosis and spongiotic vesicles (arrows) are present in this biopsy of “poison ivy.” Infiltrating lymphocytes are apparent in the epidermis, where they effect the cell-mediated delayed hypersensitivity reaction.
Allergic contact dermatitis
Numerous large granulomas fill the retic- ular dermis. Around some of the granulomas are small cuffs of lympho- cytes (arrows). The granulomas are composed of epithelioid macrophages, some of which are multinucleated (inset)
Sarcoidosis
A. The skin exhibits a typical annular plaque on the dorsal right hand. B. A central area of acellular degenerated collagen is surrounded by palisaded macrophages with the long axes of their nuclei radiating outward.
Granuloma annulare
The dermis is characterized by large, reticular collagen bundles that are oriented parallel to the epidermis. The large size and loss of basket-weave pattern of these collagen bundles are abnormal. No appendages are apparent because these structures have been destroyed.
Scleroderma
The reticular dermis is present in the upper right. Within the panniculus is a widened septum (extending through the middle of the field). Lymphocytes and macrophages are present at its interface with the adipose tissue lobules. The vessels pal- isading along the interface of the septum are infiltrated by lymphocytes.
Erythema nodosum
Honey-colored crusts secondary to rupture of vesicopustules are seen in the nasal area of a child, an area commonly colonized by Staphylococcus aureus.
Impetigo contagiosa
A leading edge of scale and erythema in a moccasin distribution characterizes this infection, most commonly caused by Trichophyton rubrum. B. A dense inflamma- tory infiltrate is present in the epidermis and dermis and is associated with the presence of fungal hyphae in the stratum corneum
Dermatophytosis / tInea pedis
Hyphae of what fungae are observed in this stratum corneum?
Dermatophytes
A Gomori methenamine silver stain highlights the organisms, which are thick-walled spores 8 to 15 microns in diameter. One of the organisms demonstrates broad-based budding.
Blastomycosis
What is making this nodule in the stratum corneum
Scabies mite
Multiple umbilicated papules in a human immunodeficiency virus (HIV)- positive patient.
Molluscum contagiosum
Name for keratinocytes infected with a poxvirus that show large eosinophilic cytoplasmic inclusions
Molluscum bodies (molluscum contagiosum)
Melanocytes are present as nests within the epidermis and dermis. An intraepidermal nest of melanocytes is surrounded by keratinocytes (inset).
Compound melanocytic nevus
Melanocytes entirely confined to the dermis
Dermal melanocytic nevus
On the right, a compound nevus is apparent with both intraepidermal and dermal components. To the left, within the epidermis, are single, atypical melanocytes within the basal layer, as well as incipient lamellar fibro- plasia. Dermal melanocytes are present below.
Compound nevus with melanocytic dysplasia.
There is bridging of rete ridges by nests of melanocytes, melanocytes with cytologic atypia (curved arrows), lamellar fibroplasia (straight arrows) and a scant perivascular lymphocytic infiltrate.
Dysplastic nevus
To the left is a zone containing typical dermal nevus cells of a compound melanocytic nevus. In the epidermis on the right is a proliferation of atypical melanocytes with lamellar fibroplasia. This photomicrograph is taken from the junction of the papular and mac- ular components of this dysplastic nevus. Dysplasia usually develops in the macular portion, which takes up most of the field.
Dysplastic nevus
Irregular melanocytic nests resting above lamellar fibroplasia (straight arrows) exhibit large epithelioid melanocytes with atypia (curved arrows).
Dysplastic nevus
Malignant melanoma of the superficial spreading type
Melanocytes grow singly within the epidermis at all lev- els and as large, irregularly sized nests at the dermal–epidermal junc- tion. Tumor cells are present in the papillary dermis (arrows), but no nest shows preferential growth over the others.
Malignant melanoma, superficial spreading type, radial growth phase.
The superficial spreading type is represented by the relatively flat, dark, brown–black portion of the tumor. Three areas in this lesion are characteristic of the vertical growth phase. All are nodular in configuration; two have a pink coloration, and the largest is a rich, ebony black.
Malignant melanoma
Vertical growth is manifested by the distinct spheroid tumor nodule to the right. This focus of melanocytes clearly has a growth advantage (larger size of the aggregate) over nests in the adja- cent radial growth phase (left).

Malignant melanoma, superficial spreading type, vertical growth phase
The host response consists of lymphocytes infiltrating amid the melanocytes (“tumor-infiltrating lymphocytes”).
Malignant melanoma, vertical growth phase
Intraepidermal growth is essentially absent. There is no radial growth lateral to the nod- ule. This tumor expands the papillary dermis and distorts the reticular dermal junction; it is therefore level III.
Malignant melanoma, nodular type
Malignan tmelanoma of the lentigo maligna type,radial growth phase.
Primary focus of growth is in the dermis
Malignant melanoma of the nodular type
Atypical melanocytes grow mostly at the dermal–epidermal interface (straight arrow), with extension down the external root sheath of follicles (curved arrow). Upward growth of melanocytes is much less prominent than in malignant melanoma of the superficial spreading type.
Lentigo maligna
Lentigo melanoma
Atypical melanocytes are present along the dermal–epidermal junction. A small dermal nest of atypical melanocytes is present (arrow).
Malignant melanoma, acral lentiginous type, princi- pally intraepidermal radial growth.
Malignant melanoma, acral lentiginous type (radial growth phase).
Large melanocytes with prominent dendrites (arrows) are present in the basilar region of the epidermis. The tumor cells contain numerous melanosomes, making the perinuclear and dendritic cytoplasms brown
Malignant melanoma, acral lentiginous type
The lesion on the heel is the primary tumor. The flat portion represents the radial growth phase, whereas the elevated portion indicates the vertical growth phase. The dark nodule on the instep is a metastasis.
Malignant melanoma, acral lentiginous type
On the left is confluent growth of atypical dermal melanocytes filling and expanding the papillary dermis.
Malignant melanoma, acral lentiginous type, vertical growth phase.
Numerous tumor-infiltrating lymphocytes (arrows) are arranged among individual tumor cells.
Malignant melanoma, vertical growth phase.
A symmetric pink nodule appeared suddenly in a child but then remained stable for several weeks until it was excised.
Spindle and epithelioid cell (Spitz) nevus
Large melanocytes with prominent nuclei. Within a hyperplastic epidermis, the melanocytes are present in large nests. Even though the cells are large and, at first glance, suggest melanoma, they are much more uniform than the cells of most malignant melanomas.
Spindle and epithelioid cell (Spitz) tumor
Within the dermis there is a poorly defined but symmetric spindle cell proliferation that is dark brown. B. The lesion is composed of elongated cells with heavily pigmented dendrites and small bland nuclei.
Blue nevus
A fair-complexioned man has a prominent brown macule that darkens in sunlight.
Freckle
The prototype of papillary epidermal hyperplasia. Squamous epithelial-lined fronds have fibrovascular cores. The blood vessels within the cores extend close to the surface of verrucae, which makes them susceptible to traumatic hemorrhage and the resultant black “seeds” that patients observe.
Verruca vulgaris
A 1-cm irregular patch of slightly variegated hyperpigmentation is present with a background of chronic solar damage.
Lentigo
Characteristic cytopathic changes occur in the outer portion of the stratum spinosum and stratum granu- losum, in which there is perinuclear vacuolization and prominent kera- tohyaline granules, with homogeneous blue inclusions (arrow).
Verruca vulgaris
Broad anastomosing cords of mature stratified squamous epithelium are associated with small keratin cysts.
Seborrheic keratosis
Cytologic atypia within the stratum basalis and lower stratum spinosum with loss of polarity. A lichenoid, band-like, lymphocytic infiltrate is frequently present. Parakeratosis is present in a small focus (arrow).
Actinic keratosis
Striking cytologic atypia of the basal keratinocytes is the hallmark of what lesion?
Actinic keratosis
A keratin-filled crater lined by glassy proliferating keratinocytes
Keratoacanthoma
Buds of atypical basaloid keratinocytes extend from the overlying epidermis into the papillary dermis. The peripheral keratinocytes mimic the stratum basalis by palisading. The separation artifact (arrow) is present because of poorly formed basement membrane components and the hyaluronic acid-rich stroma that contains collagenase.
Basal cell carcinoma, superficial type
Pearly papule: the tumor exhibits typical rolled pearly borders with telangiectases and central ulceration
Basal cell carcinoma
Sclerosing and infiltrative lesion. Irregularly branching strands of tumor cells permeate the dermis, with induction of a cellular, fibroblastic, hyaluronic acid-rich stroma.
Morpheaform basal cell carcinoma
The tumor is composed of solid nests of undifferentiated cells that resemble small cell carcinoma of the lung.
Merkel cell carcinoma
A. An ulcerated, encrusted and infiltrating lesion is seen on the sun-exposed dorsal aspect of a finger. B. The entire epidermis is replaced by atypical keratinocytes. Mitoses are apparent, as is apoptosis (arrows).
Squamous cell carcinoma in situ.
Sharply circumscribed islands of basophilic epithelial cells reside in a jigsaw puzzle–like array. Dense eosinophilic hyaline sheaths surround each island.
Cylindroma
A.Within the upper dermis is an epithelial proliferation forming ducts, tubules, and solid islands amid a dense fibrous stroma. B. The ductal differentiation closely mimics that of the straight dermal eccrine duct, with a central lumen and cuticle formation.
Syringoma
Uniform cells with narrow ductal lumina
Poroma
Fibrous tissue replaces the dermis and forms poorly defined cartwheels
Dermatofibroma
The tumor is composed of keratinized centers surrounded by basophilic epithelial cells (“horn cysts”; arrows).
Trichoepithelioma
Tumor cells form small cartwheels with central vascular spaces.
Dermatofibrosarcoma protuberans.
A.A 66-year- old woman presented with a 30-year history of erythematous scaly patches and plaques with telangiectases, atrophy and pigmentation. B. An atypical infiltrate of lymphocytes expands the papillary dermis and extends into the epidermis (“epidermotropism”).
Mycosis fungoides
Some of the lymphocytes display hyperchromatic and convoluted (“cerebriform”) nuclei
Mycosis fungoides
A.A large nodule is composed of proliferating endothelial cells forming fascicles and vascular spaces. B. A higher-power view shows cytologic atypia of the spindle cells. Red blood cells appear agglutinated (arrows). The endothelial cells, in which the agglutinated red blood cells are present, form slit-like spaces.
Kaposi sarcoma, nodule stage.
