Pathology

Question 1

Cowdry Type A Bodies

Answer 1

intranuclear eosinophilic amorphous bodies surrounded by a clear halo
- seen in VZV/HSV

Question 2

Asteroid Bodies

Answer 2

1. intracellular stellate eosinophillic inclusion bodies withing a multinucleated giant cell (sarcoidosis, foreign body rxn)
2. extracellular central spore surrounded by radiating homogeneous eosinophilic material (sporotrichosis –> splendore-hoeppli phenomenon)

Question 3

Caterpillar Bodies

Answer 3

wavy eosinophilic material in the basal epidermal layer or roof of a blister
- seen in PCT and EEP

Question 4

Donavan Bodies

Answer 4

intracytoplasmic bacteria in infected histiocytes

- seen in granuloma inguinale

Question 5

Dutcher Bodies

Answer 5

eosinophilic intranuclear inclusions of Ig in malignant plasma cells
- seen in multiple myeloma

Question 6

Henderson-Patterson Bodies

Answer 6

large eosinophilic inclusion of viral protein in keritinocytes
-seen in molluscum contagiosum

Question 7

5 cells that stain positive with S100

Answer 7

melanocytes
langerhans cells
schwann cells (nerve in general)
eccrine cells
adipocytes

Question 8

Mucin stains

Answer 8

colloidal iron, toluene blue, alcian blue

Question 9

What is Factor XIIIa positive?

Answer 9

Dermatofibroma, angiofibroma, fibrous papule of nose, acquired digital fibrokeratoma, malignant fibrous histiocytoma, xanthogranuloma

Question 10

What is CD34 positive?

Answer 10

Dermatofibrosarcoma protuberans, pleomorphic fibromas, sclerotic fibroma, spindle cell lipoma, nephrogenic fibrosing dermopathy

Question 11

What do you call a tumor made of cuboidal cells with ample pink cytoplasm and cuticle-lined ducts that connects to the epidermis? What if it is confined to the epidermis? The dermis? If not connected to epidermis?

Answer 11

Poroma; if in epidermis only - Hidroacanthoma simplex (ddx clonal SK but has ducts); if in dermis - Dermal duct tumor; if not connected to epidermis - Nodular Hidradenoma (dermal nodule)

Question 12

Staining pattern for Xanthogranuloma

Answer 12

CD68 +, Factor XIIIa +, vimentin +; CD34 -, S100 -, CD1a - (Bonus: if multiple xanthogranulomas, check eyes…increased risk glaucoma or anterior-chamber hemorrhage)

Question 13

Where can you see Touton Giant Cells?

Answer 13

Dermatofibroma (can contain hemosiderin = ringed lipidized siderophages), juvenile xanthogranuloma, necrobiotic xanthogranuloma

Question 14

Differential for neutrohils in the stratum corneum?

Answer 14

Psoriasis, Tinea, Impetigo, Candida, Seborrheic Dermatitis, Syphilis (“PTICSS”)

Question 15

Differential for painful tumors…

Answer 15

Blue rubber bleb, Leiomyoma, Eccrine spiradenoma, Neuroma, Dermatofibroma, Angiolipoma, Neurilemmoma, Endometrioma, Glomus tumor, Granular cell tumor (BLEND AN EGG)

Question 16

Paisley tie pattern Ddx:

Answer 16

Desmoplastic trichoepithelioma, morpheaform BCC, MAC, syringomas

Question 17

What is seen on staining of minocycline hyperpigmentation?

Answer 17

Perls –> hemosiderin (iron) BLUE within macrophages; Fontana Masson –> melanin BLACK

Question 18

What is the histopath Ddx of blue tumors?

Answer 18

“LEMONS” = lymphoma, Ewing’s sarcoma, Merkel cell carcinoma + Melanoma, Oat cell carcinoma of lung, Small cell endocrine carcinoma

Question 19

Ddx of flame figures? What are flame figures made of?

Answer 19

Eosinophilic cellulitis (Wells syndrome), arthropod bites and stings (tick, bee, flea, spider), mastocytomas, scabies, prurigo nodularis, eczema, dermatophyte infections

Made of necrobiotic collagen and major basic protein (from eos)

Question 20

Where do mast cells live and what stains them?

Answer 20

Greatest density in papilary dermis; Giemsa stains granules purple; Leder stains granules red.

Question 21

What is the differential diagnosis of a Grenz zone?

Answer 21

Granuloma faciale, lepromatous leprosy, leukemia cutis, B-cell lymphomas

Question 22

What is the differential diagnosis of striking upper dermal edema?

Answer 22

“PUBES” = PMLE (lymphs superficial and deep), Pernio, Urticaria, Bug bite, EM (superficial lymphs), Sweets (neuts)

Question 23

What is the normal skin ddx on histopathology?

Answer 23

Tinea, Ichthyosis, Porokeratosis, Inferface dermatitis (GVHD and DM can be subtle), Vitiligo, Alopecia, Myxedema, Scleromyxedema, Connective tissue abnormalities (nevi, anetoderma), Argyria, Urticaria, TMEP

Question 24

What is the Ddx of a square punch biopsy?

Answer 24

Pretybial myxedema, morphea, scleroderma, scleredema, NLD

Question 25

What is the histological Ddx of nodular lymphoid infiltrate?

Answer 25

Seven Ls

Lupus
polymorphous Light eruption
Lymphoma
Lymphocytoma cutis
Lichen striatus
Lymphocytic eruption of Jessner and Kanoff
Lues

Question 26

What IHC, if positive, makes a biopsy consistent with primary cutaneous follicle center lymphoma more likely to be a systemic follicle center lymphoma?

Answer 26

Bcl-2

Bcl-2 results in a 14;18 translocation, which is found in 85-90% of systemic follicle center lymphomas. Only 10-40% of primary cutaneous follicle center lymphomas are Bcl-2 positive. No reactive lymphoid infiltrates are Bcl-2 positive.

Question 27

What is the name of the condition and the immunohistochemistry for the solitary variant of mycosis fungicides that is most common on a distal extremity?

Answer 27

Pagetoid reticulosis

CD3+…can be CD4/CD8+ or CD4/CD8-