KS

Skin & Soft Tissue Lesions

Overview & Scope

  • Focus of lecture: skin & soft-tissue lesions seen on a surgical rotation.

    • Predominantly benign vs malignant neoplasms.

    • Infectious entities included (surgical site infection, cellulitis, abscess, NSTI).

    • Burns discussed in separate lecture

Skin Anatomy & Potential Neoplasm Origins

  • Epidermis (outermost)

    • Produces keratin; multiple sub-layers.

    • Neoplasms arising here: squamous cell carcinoma (SCC), basal cell carcinoma (BCC).

    • Stratum basale contains melanocytes → melanoma originates here.

  • Dermis

    • Contains sweat glands, hair follicles.

    • Lesions: Kaposi sarcoma, keloids.

  • Hypodermis / subcutaneous tissue

    • Rich in lymphatics, arteries, veins, nerves.

    • Tumors: schwannomas, neurofibromas.

Clinical Evaluation of Skin Lesions

  • History

    • Duration & tempo of growth.

    • Symptom changes: itching, bleeding, pain, color evolution/darkening.

    • Past lesions/skin cancer; prior surgery, trauma, radiation to area.

    • Immunosuppressive states (drugs, organ transplant, systemic disease).

    • Genetic disorders: neurofibromatosis, tuberous sclerosis.

    • Family history of skin cancers or neoplasms.

    • Social: occupational & recreational UV exposure, tobacco, environmental irritants.

  • Physical exam

    • Complete skin survey (scalp → soles, interdigital, axillae).

    • Inspect & palpate regional lymph-node basins relevant to lesion site.

    • Melanoma red-flags: ABCDE mnemonic

    • A – Asymmetry

    • B – Border irregularity

    • C – Color variegation

    • D – Diameter >(6\text{ mm}) (classic cutoff)

    • E – Elevation / Evolution (recent changes in lesion)

Diagnostic Biopsy Techniques

  • Shave biopsy

    • Tangential slice of raised lesion; quick, minimal depth info.

    • NOT appropriate when melanoma is suspected (destroys depth measurement).

  • Punch biopsy

    • Cylindrical core through epidermis → dermis ± hypodermis; preserves architecture & depth.

    • Preferred for pigmented or flat lesions, suspected melanoma.

  • Excisional biopsy

    • Local anesthetic → complete removal with narrow margin; diagnostic & (maybe) therapeutic.

    • Ideal for small pigmented lesions where melanoma is possible.

Common Benign & Infectious Conditions

  • Surgical site infection (SSI)

    • Erythema, warmth, tenderness around wound ≈ 3{-}7 days post-op.

    • No fluctuance/abscess; treat with antibiotics & local care.

  • Cellulitis

    • Diffuse dermal infection; erythema, warmth, tenderness without pus pocket.

    • Managed with systemic antibiotics alone.

  • Abscess

    • Localized collection of pus; often surrounded by cellulitis.

    • Requires incision & drainage (I&D); antibiotics adjunctive.

Necrotizing Soft Tissue Infection (NSTI / Necrotizing Fasciitis)

  • Definition

    • Rapidly progressive infection tracking along fascial planes → toxin-mediated tissue necrosis.

  • Pathophysiology

    • Bacterial toxins → intense inflammation → obliterative endarteritis, thrombosis, tissue ischemia/necrosis.

  • Risk factors

    • Skin injury/trauma, recent surgery.

    • Immunosuppression, diabetes, obesity.

    • Extremes of age, frailty.

    • Peripheral vascular disease (poor perfusion).

  • Common pathogens

    • Group A Streptococcus, Staphylococcus aureus, Clostridium spp., E.\ coli.

  • Clinical diagnosis (imaging/calculators are adjunct). NSTI remains a clinical diagnosis—maintain high suspicion and act on subtle clues .

    • Toxic appearance: fever, tachycardia, hypotension.

    • Pain out of proportion to exam.

    • Rapidly expanding erythema (markable hour-to-hour growth).

    • Ecchymotic/hemorrhagic bullae

    • Crepitus from subcutaneous gas.

    • Laboratory red-flags: marked leukocytosis, anemia, hyponatremia, hyperglycemia, elevated creatinine/lactate.

    • Skin necrosis/black eschar = late finding.

  • Management

    • ABCs: airway, breathing, circulation; aggressive fluid resuscitation; vasopressors prn.

    • Broad-spectrum antibiotics covering gram+ cocci, gram– rods, anaerobes:

      • Options: carbapenem OR piperacillin-tazobactam + vancomycin (MRSA) + clindamycin (toxin inhibition).

    • Emergent surgical exploration & radical debridement to viable fascia/muscle/skin; often multiple returns & subsequent reconstruction.

Malignant Skin Neoplasms

Common Risk Factors

  • Ultraviolet radiation (cumulative & intense exposure).

  • Immunosuppression (organ transplant, chronic steroids, biologics, HIV).

Basal Cell Carcinoma (BCC)

  • Origin: basal keratinocytes of epidermis.

  • Clinical appearance: shiny, pearly papule/nodule with rolled borders ± telangiectasias.

  • Diagnosis: biopsy.

  • Treatment

    • Standard excision with 4\text{ mm} clinical margins.

    • Mohs micrographic surgery for cosmetically sensitive areas (face, eyelids, nose, ears) to preserve tissue while ensuring clear margins.

Squamous Cell Carcinoma (SCC)

  • Origin: squamous keratinocytes; frequently evolves from actinic keratosis (premalignant epidermal dysplasia).

  • Presentation: scaly, erythematous plaque or nodule; may ulcerate or crust.

  • Diagnosis: biopsy.

  • Treatment: excision with 4{-}6\text{ mm} margins; Mohs an option on high-risk sites.

Merkel Cell Carcinoma

  • Rare neuroendocrine cutaneous malignancy linked to Merkel cell polyomavirus.

  • Aggressive behavior; management often multimodal (wide excision, lymph-node evaluation, radiation, systemic therapy).

Melanoma

Types
  • Superficial spreading (most common).

  • Nodular.

  • Acral lentiginous (palms, soles, nail beds; more common in darker-skinned patients).

Work-up & Full Exam
  • Comprehensive H&P; inspect entire skin surface.

  • Evaluate regional lymph-node basin:

    • Arm/hand → axillary nodes.

    • Head/neck → cervical nodes.

    • Leg/foot → inguinal nodes.

  • Biopsy MUST provide depth → excisional or punch; avoid shave.

Pathology Report Essentials
  • Breslow thickness (tumor depth in mm).

  • Ulceration status.

  • Mitotic rate (per \text{mm}^2).

Surgical Management: Primary Site (Wide Local Excision = WLE)

Melanoma Category

Required Margin

Melanoma in situ

5{-}10\text{ mm}

Invasive <1\text{ mm}

1\text{ cm}

Thickness 1{-}2\text{ mm}

1{-}2\text{ cm} (lean toward 2\text{ cm} if laxity allows)

≥2\text{ mm}

2\text{ cm}

  • Even if biopsy “removed” lesion, still perform WLE around scar.

  • Incision design: elliptical/oval with length ≈ 3\times width to facilitate linear closure; deeper/wider defects may need flap or skin graft.

Regional Lymph-Node Management
  • Clinically negative nodes + melanoma thickness ≥1\text{ mm} (SLNB generally not required if <0.7 mm depth, can consider SLNB if depth 0.8-1 mm esp if risk factors like high mitotic rate or ulceration present):

    • Perform Sentinel Lymph Node Biopsy (SLNB) in corresponding basin during WLE.

    • SLNB negative → no further nodal surgery.

    • SLNB positive → options:

      • Completion lymph-node dissection.

      • Active nodal surveillance with serial ultrasound (supported by MSLT-II trial), generally preferred.

  • Palpable/enlarged nodes

    • First step: needle/core biopsy to confirm metastatic melanoma.

    • If positive → therapeutic complete node dissection + WLE of primary site.

Systemic / Adjuvant Therapy for Melanoma
  • Immunotherapy (e.g., anti-PD-1, anti-CTLA-4 antibodies).

  • Molecular targeted therapy for BRAF-mutant tumors (BRAF ± MEK inhibitors).

  • Consider in stage III (node-positive) and stage IV disease or high-risk resected melanomas.