Skin & Soft tissue

Question 1

Hurley Classification of Hidradenitis Suppurativa

Answer 1

Hurley Stage I: localized abscesses; no sinus tract, no scars
Hurley Stage II: recurrent abscesses, +sinus tracts, +scars, separated by areas of normal skin
Hurley Stage III: diffuse dz, multiple connected sinus tracts/abscesses/scars affecting entire area

Question 2

Treatment of Hidradenitis Suppurativa based on Hurley Stage

Answer 2

HS I: Topical clina, antiseptic (chlorhexidine) washed, lifestyle mods

HS II: PO Doxy, +/- adalimumab

HS III: PO Doxy, PO Clinda/Rifampin/Antiandrogens (for refractory dz), +/- adalimumab, Surgical excision + STSG (for refractory dz to max medical tx)

Question 3

Burns classification

Answer 3

1st degree: only epidermis (red, without blisters)
2nd degree: extends into dermis (painful, blisters)
superficial partial thickness: papillary dermis (moist, blanches)
deep partial thickness: reticular dermis (dry, less blanching, insensate)
3rd degree (full thickness): entire dermis (leathery, painless)
4th degree: into underlying fat, muscle, bone (black, eschar)

Question 4

Nonmelanoma skin cancer (NMSC)

Answer 4

MC skin cancer. 2/2 to UV ray exposure.

Basal cell carcinoma

Squamous cell carcinoma: actinic keratosis is precursor

Question 5

Actinic keratosis

Answer 5

Can progress to SCC

small, 3-10mm, sandpaper-like spots, on elderly, fair-skinned, sun sensitive areas

Tx: topical chemo (5-FU), photodynamic tx, topical immune modulator (Imiquimod), cautery & destruction, cryosurgery, cautery & curettage, shave excision, cosmetic resurfacing (dermabrasion/chemical peels)

Question 6

MC type of collagen in a scar?

Answer 6

Type I

Collagen = principal structural protein in tissues

Made of 2 amino acids: hydroxyproline and hydroxylysine

Hydroxylation needs ascorbic acid, important for stabilization and cross-linking of collagen.

Type I collagen: predominant collagen in body, healed wounds, and scars

Type II: cartilage

Type III: blood vessels, fetal skin, uterus

Type IV: basement membrane

Type V: cornea

Question 7

Fothergill’s sign

Answer 7

rectus sheath hematoma that remains unchanged with contraction of rectus muscles

Question 8

palpable abdominal mass, most often below the umbilicus, noted in sitting or lying position that remains unchanged with contraction of rectus muscles (Fothergill’s sign)

Answer 8

Rectus sheath hematoma

Question 9

Types of rectus sheath hematomas

Answer 9

I: hematoma is intramuscular, increase in size of muscle seen, ovoid or fusiform shape, unilateral, doesn’t dissect along fascial planes. Tx: d/c home

II: intramuscular but blood between muscle and transversals fascia, bilateral, blood in prevesical space. Tx: admit for obs

III: blood b/w transversals fascia and muscle, in peritoneum, and prevesical space. Tx: angioembolization

Question 10

Decrease risk of SSI following ostomy closure by?

Answer 10

purse-string closure technique

avoids open wound, lowest wound infection rate

Question 11

Merkel cell carcinoma

Answer 11

Arise from Merkel cells of epidermis and hair follicle

Lesions are raised, purple, subcutaneous nodukes

Histo: monomorphic cells, large pale nuclei, scant cytoplasm, whorled paranuclear plaques; +CK20, -TTF1

Question 12

Radiation induced skin ulcer

Answer 12

sxs: pruritus, pain
hx of radiation

histo: epidermal atrophy, dermal sclerosis (eosinophilic homogenized sclerosis of dermal collagen), dilated superficial blood vessels, loss of adnexal structures (hair follicles, sweat ducts), increased atypical stellate-shaped fibroblasts
tx: conservative wound care (1st), aggressive radical excision w/ recon (2nd line)

Question 13

Pressure injury staging

Answer 13

Stage I: intact skin, localized nonblanching erythema

Stage II: partial thickness skin loss, exposed dermis

Stage III: full-thickness skin loss, exposed fat and granulation tissue

Stage IV: full thickness skin and tissue loss, exposed fascia, muscle, tendon, cartilage, bone

Question 14

Lymphangitis

Answer 14

Infection of superficial lymphatic vessels

MCC: group A strep (strep pyogenes)

Streaking erythema, warmth, tenderness, induration, lymphadenopathy, hx of trauma to affected area

Tx: I&D of entry wound, Abx

Question 15

Basal cell carcinoma

Answer 15

excision w/ 0.5cm margins

pearly, rolled edges, pink/brown/black

Question 16

Necrotizing fasciitis

Answer 16

Type 1: polymicrobial (MC)
Type 2: monomicrobial (Group A strep, Staph/MRSA)
Type 3: Trauma, marine (Clostridium, vibrio)
Type 4: Fungal (Candida)

High suspicion -> surgical exploration & debridement
Low suspicion -> Labs & imaging
MR/CTs are highly sensitive but not specific
XR showing subQ gas in ~30% of NSTIs

Question 17

Dermatofibrosarcoma protuberans (DFSP)

Answer 17

Flesh colored mass
Dermal or subdermal tumor, no penetration into epidermis

Histo: proliferation of spindle-shaped tumor cells involving dermis and subcutaneous adipose tissue; tentacles extend laterally from the lesion

tx: en bloc excision w/ wide margin (2-4cm)

t(17;22)(q22;q13) translocation - fuses COL1A1 and PDGFB genes

Imatinib (PDGFB rec blocker) can downstage locally advanced tumor

+CD34, +vimentin
-Factor XIIIa, -alpha-smooth muscle actin

Question 18

Strongest independent prognostic factor of soft tissue sarcomas, independent indicator of degree of malignancy, and probability of distant mets & death

Answer 18

histo grading

Question 19

Soft tissue sarcoma

Answer 19

~80% originate from soft tissue, rest from bone
Dx: CNBx

Histo grading system:

1) Tumor differentiation
2) Mitotic count
3) Tumor necrosis

Grade 1 (<3), Grade 3 (>5)

Well-differentiated: liposarcoma, leiomyosarcoma
Poorly-differentiated: pleomorphic sarcomas, synovial sarcomas, osteosarcoma, PNET

Question 20

Undifferentiated spindle cell tumor

Answer 20

MC location: prox tibia, distal metaphyses of femur

Radiography: loss of normal trabeculation, cortical destruction, adjacent soft tissue invasion, mass

Imaging of choice: MRI w/ contrast

Path: high-grade (>90%), fibroblasts, whirling pattern, multinucleated giant cells, inflammatory cells, foamy mononuclear giant cells

Tx: neoadjuvant chemo (relieve pain, decrease edema, contracture, size), urgent surgical resection w/ wide margins

Question 21

Steps for skin graft healing

Answer 21

Imbibition -> inosculation -> revascularization

Imbibition: day 0-2, gets nutrients from plasma through direct contact

Inosculation: day 2-3, progressive anastomosis of transected vessels

Revascularization: new vessels from capillary bed

Question 22

Tx of metastatic melanoma

Answer 22

If neg for anti-programmed cell death protein (PD1) & pos for BRAF -> ipilimumab (cytotoxic T-lymphocyte Ag-4 - CTLA-4; blocking antibody). humanized IgG1-kappa monoclonal Ab that competitively inhibits CTLA-4 negative regulatory checkpoint. Improves overall and progression-free survival.

Nivolumab: PD-1 inhibitor (good for metastatic melanoma with pos PD-1

Vemurafenib: used in unresectable melanomas with V600E mutations in BRAF gene

Question 23

Temperature at which collagen uncoils

Answer 23

45C (113F)

Question 24

Temp at which protein denaturation occurs, coagulation necrosis begins

Answer 24

60C (140F)

Question 25

Temp at which carbonization begins, drying and shrinkage of tissue

Answer 25

80C (176F)

Question 26

Temp at which cell vaporization and vacuoles form causing cell destruction

Answer 26

100C (212F)

Question 27

Temp at which oxidation of protein/lipids -> carbon residue or eschar formation

Answer 27

125C (257F)

Question 28

Familial BK Mole Syndrome mutation

Answer 28

p16, CDKN2A gene

Question 29

Melanoma tumor markers

Answer 29

S-100+
HMB45
Tyrosinase
V600E