3
Cell Type

  • Melanocytic, 155
  • Spindle cells, 164
  • Endothelial, 178
  • Giant, 192
  • Clear, 202

    Blue nevus

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  • Melanocytes
  • Cells are small and spindled/dendritic with occasional cells containing melanin pigment
  • Dermis often hyalinized
  • Melanophages often present

    Deep penetrating nevus

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  • Melanocytes
  • Epithelioid melanocytes are admixed with or bordered by uniformly distributed melanophages
  • Pattern on low power is wedge-shaped (often centered around a follicle)

    Melanoma

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  • Melanocytes
  • Cells are confluent at the junction with irregularly sized nests, scattered high and low within the epidermis
  • Atypical cells and mitoses in epidermal and dermal nests

    Mongolian spot

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  • Dendritic melanocytes distributed throughout the dermis

    Pigmented spindle cell nevus of Reed

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  • Melanocytes
  • Pigmented spindle cells are arranged in vertical fascicles in the base of the epidermis
  • Pushing margin into superficial dermis

    Recurrent nevus

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  • Melanocytes
  • Cells are in irregularly shaped nests, sometimes confluent, confined to area above a dermal scar
  • Predominantly junctional involvement

    Spitz nevus

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  • Melanocytes, spindled and epithelioid
  • Cells are in vertical fascicles within the epidermis (“school of fish”)
  • Well-circumscribed and symmetric
  • Kamino bodies
  • Clefting above nests
  • Cells are atypical but all resemble each other

    Key differences

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    (b)

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    (c)

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    (d)

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    (e)

    1. Blue nevus: finely pigmented spindle/dendritic cells and melanophages within the dermis
    2. Intradermal nevus: circular melanocytes with fine brown pigment in nests (clusters)
    3. Deep penetrating nevus: epithelioid melanocytes in clusters with surrounding melanophages
    4. Mongolian spot: dendritic melanocytes infiltrating between collagen bundles
    5. Melanoma, desmoplastic: atypical spindle cells (see page 165)

      Key differences, continued

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      (g)

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      (h)

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      (i)

    6. Melanoma – Atypical cells in irregular pattern in epidermis and dermis, asymmetric, dermal mitoses
    7. Recurrent nevus – Irregular nests of pigmented cells above a scar
    8. Spitz nevus – Vertically arranged epithelioid and spindle cells, symmetric
    9. Pigmented spindle cell nevus of Reed – Vertically arranged pigmented spindle cells in base of epidermis with pushing margin into dermis

      Blue nevus, cellular

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  • Melanocytes that are spindled (and also appear rounded when fascicles are cut cross-wise) (so-called biphasic pattern)
  • Often bulbous into the deep dermis
  • Scattered melanin pigment within the cells

    Melanoma, desmoplastic

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  • Melanocytes
  • Cells are spindled and arranged in bundles infiltrating through collagen
  • Cells are atypical
  • Often overlying in situ-melanoma changes in epidermis
  • Perivascular lymphocytes are a clue

    Dermatofibroma

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  • Short spindle cells (fibrohistiocytes) in a “busy dermis”
  • Epidermis often acanthotic and pigmented
  • May have basaloid buds or sebaceous lobules at base of epidermis
  • Cells entrap collagen at the periphery (arrows)
  • Collagen bundles appear to be “coming at you” (90° to slide surface)

    Dermatofibrosarcoma protuberans

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  • Spindle cells (fibrocytes) filling dermis
  • Cells are monomorphous and arranged in a storiform (cartwheel) pattern
  • Infiltration into the fat in layered or honeycomb pattern

    Scar

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  • Spindle cells (fibrocytes)
  • Cells are arranged parallel to epidermis
  • Vessels oriented perpendicular to epidermal surface

    Infantile digital fibromatosis

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  • Spindle cells (myofibroblasts)
  • Cells have round pink cytoplasmic inclusions (arrows)
  • Cells are arranged in long fascicles

    Nodular fasciitis

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  • Spindle cells (myofibroblasts)
  • Myxoid areas of elongated cells with oval nuclei with tapered ends and elongated cytoplasm (“tissue-culture fibroblasts”)
  • Extravasated erythrocytes
  • Mitoses may be seen
  • Radial arrangement of blood vessels at periphery
  • Deep tumor, often no epidermis present

    Leiomyoma

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  • Spindle cells (smooth muscle cells)
  • Cells are arranged in fascicles which intersect at 90 degree angles
  • Cigar-shaped nuclei (arrows)

  • Cells cut in cross-section have perinuclear vacuoles around round nuclei

    Note Normal nipple has small bundles of smooth muscle cells (same appearance as an accessory nipple, see page 78).

    Neurofibroma

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  • Spindle cells (neural – pericytes)
  • Cells have thin, wavy nuclei (long arrow)
  • Light pink stroma
  • Scattered mast cells (short arrow)
  • Not encapsulated

    Palisaded encapsulated neuroma

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  • Spindle cells (neural – Schwann cells)
  • Cells are arranged in fascicles with characteristic clefting
  • Often not truly encapsulated

    Schwannoma

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  • Spindle cells (neural – Schwann cells)
  • Antoni A areas – cellular
  • Antoni B areas – myxoid
  • Verocay bodies (arrows) – palisaded arrangement of nuclei around a central pink area of collagen
  • Encapsulated
  • Vascular spaces may be very dilated
  • Often a deep tumor with no epidermis present

    Kaposi sarcoma, nodular

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  • Spindle cells, hyperchromatic (endothelial cells)
  • Interspersed erythrocytes
  • Intracytoplasmic pink globules (erythrophagolysosomes) (arrows)

    Key differences

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    (c)

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    (d)

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    (e)

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    (f)

    1. Blue nevus, cellular: spindled melanocytes with fine melanin pigment in the cytoplasm; fascicular arrangement
    2. Desmoplastic melanoma: spindled atypical melanocytes in fascicles; often overlying melanoma in situ
    3. Dermatofibroma: fibrohistiocytic cells with collagen entrapment at periphery, epidermal acanthosis
    4. Dermatofibrosarcoma protuberans: monomorphous fibroblastic spindle cells in cartwheel arrangement; infiltration into fat
    5. Infantile digital fibromatosis: spindled myofibroblasts with bright pink cytoplasmic inclusions
    6. Kaposi sarcoma, nodular: atypical spindled endothelial cells with interspersed erythrocytes and intracytoplasmic erythrophagolysosomes

      Key differences, continued

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      (h)

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      (l)

    7. Leiomyoma: smooth muscle cells (cigar-shaped nuclei with perinuclear clear space) in long fascicles
    8. Neurofibroma: pericytes with wavy nuclei, mast cells, bubble-gum pink stroma
    9. Nodular fasciitis: elongated myofibroblasts in loose stroma, extravasated erythrocytes, often deep in the fat
    10. Palisaded encapsulated neuroma: clefts between collections of spindle cells (Schwann cells) with nuclear palisading
    11. Scar: spindle cells (fibroblasts) arranged parallel to epidermal surface
    12. Schwannoma: Schwann cells with particular architectural features – Verocay bodies, myxoid areas, encapsulation

    Angioleiomyoma

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  • Endothelial cells (suggestion of vessels)
  • Circular pink ball in dermis
  • Scar-like appearance
  • Mass composed of smooth muscle cells (cigar-shaped nuclei – long arrow) with compressed vessels (short arrows) (sometimes dilated)

    Angiolymphoid hyperplasia with eosinophilia

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  • Endothelial cells (and vessels)
  • Numerous vessels with epithelioid (“hobnail”) endothelial cells (arrow) surrounded by inflammation
  • Clusters of epithelioid endothelial cells may mimic granulomas
  • Eosinophils may be prominent

    Angiosarcoma

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  • Endothelial cells (suggestion of vessels)
  • Dissection of collagen bundles by a maze-like arrangement of vessels lined by atypical cells
  • Papillary endothelial fronds (papillated clusters of endothelial cells)
  • Deeply infiltrative

    Bacillary angiomatosis

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  • Endothelial cells (and vessels)
  • Superficial vessels surrounded by plasma cells and “clouds” of organisms (arrow) that stain with silver

    Chondrodermatitis nodularis helicis

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  • Endothelial cells (and vessels)
  • Hyperkeratosis
  • Central erosion/ulceration of epidermis with underlying pink fibrin and flanking vessels
  • Vascular ectasia with plump endothelial cells
  • Cartilage may be present beneath fibrin

    Dermatofibroma, hemosiderotic

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  • Suggestion of vessels
  • Epidermal acanthosis
  • Touton giant cells with rim of hemosiderin pigment as well as spindle and epithelioid cells

    Fibrous papule

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  • Endothelial cells (and vessels)
  • Fibrotic stroma
  • Concentric fibrosis around vessels/adnexae (long arrow)
  • Stellate fibroblasts (short arrow)

    Infantile hemangioma

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  • Endothelial cells (suggestion of vessels)
  • Lobules of small blue cells
  • Scattered spaces containing erythrocytes within the lobules

    Kaposi sarcoma, patch/plaque

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  • Endothelial cells (suggestion of vessels)
  • Vessels forming around other vessels (promontory sign)
  • Vessels may be lined by inconspicuous endothelial cells

    Pyogenic granuloma

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  • Endothelial cells (and vessels)
  • Lobules of dilated vessels embedded in loose stroma with inflammatory cells

    Stasis dermatitis

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  • Endothelial cells (and vessels)
  • Hyperkeratosis
  • Variable spongiosis
  • Small caliber thick-walled capillaries in clusters in the upper dermis (arrows)
  • Hemosiderin

    Targetoid hemosiderotic (hobnail) hemangioma

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  • Endothelial cells (and vessels)
  • Somewhat wedge-shaped arrangement of vessels
  • Biphasic with slightly dilated vessels centrally and compressed vessels at periphery
  • Hemosiderin (arrow) around the peripheral vessels

    Key differences

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    (d)

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    (e)

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    (f)

    1. Angioleiomyoma: well-circumscribed pink ball composed of cigar-shaped spindle cells and compressed to dilated vessels
    2. Angiolymphoid hyperplasia with eosinophilia: dilated vessels with prominent hobnail endothelial cells surrounded by inflammation, +/– numerous eosinophils
    3. Angiosarcoma: maze-like connection of vessels lined by atypical endothelial cells
    4. Bacillary angiomatosis: dilated vessels surrounded by inflammation that includes plasma cells and ill-defined “clouds”
    5. Chondrodermatitis nodularis helicis: dilated vessels on either side of fibrin; epidermis may be eroded/ulcerated or acanthotic/atrophic
    6. Dermatofibroma, hemosiderotic: histiocytes and giant cells with hemosiderin

      Key differences, continued

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      (h)

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      (i)

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      (k)

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      (l)

    7. Fibrous papule: fibrotic stroma with stellate fibroblasts and dilated vessels
    8. Infantile hemangioma: lobules of small blue cells with interspersed spaces containing erythrocytes
    9. Kaposi sarcoma, patch/plaque: slit-like or angulated spaces dissecting through collagen; vessels around vessels
    10. Pyogenic granuloma: clusters of dilated vessels surrounded by mixed inflammation
    11. Stasis dermatitis: small clusters of capillaries in upper dermis with hemosiderin
    12. Targetoid hemosiderotic hemangioma: wedge-shaped area of increased vessels with hemosiderin at periphery

    Atypical fibroxanthoma

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  • Giant cells with bizarre nuclei
  • Cells are atypical
  • Mitoses
  • Often a grenz zone above the atypical cells and solar elastosis flanking the atypical cells

    Giant cell tumor of tendon sheath

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  • Giant cells of osteoclastic type (nuclei arranged haphazardly on one side of the cell)
  • Nuclei of giant cells resemble the nuclei of adjacent histiocytes
  • Hemosiderophages
  • Often a deep tumor (no epidermis present)

    Juvenile xanthogranuloma

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  • Touton giant cells (wreath of nuclei with pink center and foamy cytoplasm outside the wreath) arranged at periphery of collection of histiocytes
  • Eosinophils may be present
  • Scattered foamy cells may be present

    Reticulohistiocytosis

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  • Oncocytic giant cells (multinucleated cells with ground glass pink cytoplasm) (arrow)

    Rosai-Dorfman disease

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  • Giant cells and interspersed collections of lymphocytes giving an alternating pink and blue color
  • Giant cells show emperipolesis (intact inflammatory cells in the cytoplasm); the giant cells are S-100 positive

    Ruptured cyst/keratin granuloma

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  • Foreign-body giant cells (haphazardly arranged nuclei), neutrophils
  • Keratin spicules can be seen near/engulfed by multinucleated cells

    Sarcoidosis

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  • Langhans giant cells (nuclei arranged in a horseshoe shape) (arrow)
  • Epidermis usually normal
  • Giant cells within collections of histiocytes that are usually “naked” (lacking surrounding lymphocytes)

    Suture granuloma

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  • Foreign-body giant cells
  • Cells surrounding suture material (braided in this case)

    Key differences

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    (d)

    1. Atypical fibroxanthoma: atypical nuclei, mitoses
    2. Giant cell tumor of tendon sheath: osteoclastic giant cells
    3. Juvenile xanthogranuloma: Touton giant cells
    4. Reticulohistiocytosis: oncocytic giant cells
    5. Rosai-Dorfman disease: giant cells with emperipolesis (other inflammatory cells within the cytoplasm)

      Key differences, continued

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      (e)

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      (f)

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      (g)

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      (h)

    6. Ruptured cyst/keratin granuloma: foreign-body giant cells, keratin spicules
    7. Sarcoidosis: Langhans giant cells, naked granulomas (arrow)

    8. Suture granuloma: foreign-body giant cells, suture material

      Note Infections and scars are other common entities that frequently have giant cells.

      Note This list is of the classical type of giant cell for each entity; none of the giant cells are pathognomonic.

    Cryptococcosis, gelatinous

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  • Clear “cells”
  • The organisms (long arrows) are surrounded by capsules, which are seen in sections as clear spaces (short arrows)

    Granular cell tumor

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  • “Clear” cells
  • Epidermis may be acanthotic or display pseudoepitheliomatous hyperplasia
  • Cells are polygonal to oval and contain a granular pink material (phagolysosomes)
  • Large granules are surrounded by haloes

    Hibernoma

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  • “Clear” cells
  • Cells are adipocytes that are so-called “mulberry” cells, with a net-like vacuolar pattern around the nuclei

    Histoplasmosis

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  • “Clear” cells
  • Cells are macrophages that contain the organisms
  • Organism is encapsulated so is often surrounded by a clear space

    Leishmaniasis

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  • “Clear” cells
  • Cells are macrophages that contain the organisms
  • Organisms may cluster at periphery of the macrophages

    Lepromatous leprosy

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  • “Clear” cells
  • Cells are histiocytes (“Virchow cells”) that look subtly foamy and are filled with organisms (seen with special stains)
  • Vacuoles with clusters of organisms (globi)
  • On low power, the histiocytes are arranged in linear configurations
  • Grenz zone present
  • Nerves may appear thickened

    Lipoma (left) / Angiolipoma (right)

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  • “Clear” cells with compressed peripheral nucleus (arrow, left lower image)
  • Clear cells are adipocytes, arranged in lobules
  • Decreased/absent septae
  • Angiolipoma also has an increased number of small vessels, some containing fibrin (arrows, right lower image)

    Melanoma, balloon cell

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  • “Clear” cells
  • Cells are melanocytes that have clear/foamy cytoplasm
  • Cells have atypical nuclei (arrows)
  • Special stains may be necessary to confirm the diagnosis
  • Foci of conventional melanoma or a junctional component as clues

    Nodular hidradenoma

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  • “Clear” cells
  • Cells are arranged in lobules with areas of ductal differentiation
  • Hyalinized collagen often present

    Renal cell carcinoma

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  • “Clear” cells
  • Often in cords, islands or pseudoglandular structures
  • Cells are of renal origin and are surrounded by prominent blood vessels/extravasated erythrocytes

    Sebaceous adenoma

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  • “Clear” cells
  • Cells are sebocytes often with spiky/scalloped nuclei bordered by several layers of basaloid cells (arrows)
  • Generally on low power is a downward lobular proliferation from the epidermis

    Xanthelasma

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  • “Clear” cells
  • Cells are foamy histiocytes (filled with lipid), arranged in between collagen bundles
  • Often a thin epidermis (eyelid skin)
  • Vellus hairs may be present (eyelid skin)

    Xanthogranuloma (older lesion)

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  • “Clear” cells
  • Cells are histiocytes, arranged in a well-circumscribed mass in the upper dermis
  • Touton giant cells and eosinophils often seen

    Xanthoma

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  • “Clear” cells
  • Cells are foamy histiocytes (filled with lipid), in clusters in the dermis
  • Free lipid is present in eruptive xanthomas

    Key differences

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    (f)

    1. Cryptococcosis, gelatinous: clear spaces representing the capsule of the organism
    2. Granular cell tumor: cells with grainy cytoplasm
    3. Hibernoma: cells with net-like vaculolated cytoplasm
    4. Leishmaniasis: macrophages filled with organisms
    5. Lepromatous leprosy: histiocytes filled with organisms; linear arrangement on low power
    6. Histoplasmosis: histiocytes with intracytoplasmic round organisms; organisms often surrounded by a clear space (the capsule)

      Key differences, continued

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      (l)

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      (m)

    7. Melanoma, balloon cell: atypical nuclei with clear cytoplasm
    8. Nodular hidradenoma: clear cells with interspersed ducts and hyalinized collagen
    9. Renal cell carcinoma: clear cells with extravasated erythrocytes
    10. Sebaceous adenoma: clear sebocytes with star-shaped nuclei with a rim of basaloid cells
    11. Xanthelasma: foamy cells interspersed in eyelid skin
    12. Xanthogranuloma: foamy cells with some Touton cells
    13.  Xanthoma: foamy cells and extracellular lipid