Melanoma Prognosis
Breslow thickness (vertical depth of invasion from granular layer) is the single most important prognostic factor for cutaneous melanoma.
Basal Cell Carcinoma (BCC)
Pearly, translucent papule with central ulceration ('rodent ulcer') and arborizing telangiectasias on sun-exposed head/neck; palisading basaloid cells.
Squamous Cell Carcinoma (SCC)
Hyperkeratotic, ulcerated crusted plaque on lower lip or ears; arises from Actinic Keratosis; keratin pearls and intercellular bridges on histology.
Necrotizing Soft Tissue Infection
Severe pain out of proportion to exam, crepitus, rapid bullous progression, dusky skin discoloration; surgical emergency with immediate surgical debridement.
Cutaneous Malignancies: Melanoma vs. BCC vs. SCC
| Malignancy | Clinical Appearance & Risk Factors | Histopathologic Hallmarks | Staging & Curative Treatment |
|---|---|---|---|
| Basal Cell Carcinoma (BCC) | Most common skin cancer; pearly papule with arborizing telangiectasias, rolled border, central crater/ulcer; sun-exposed head/neck | Nests of basaloid cells with peripheral palisading and retraction artifact from surrounding stroma | Surgical excision with 4 mm margins; Mohs micrographic surgery for cosmetically sensitive facial areas; locally invasive, rarely metastasizes |
| Squamous Cell Carcinoma (SCC) | Second most common; scaling, indurated, crusted ulcerated plaque; precursor lesion: Actinic Keratosis (sandpaper-like rough macules); chronic draining sinuses (Marjolin ulcer) | Sheets of atypical keratinocytes with keratin pearls and prominent intercellular bridges (desmosomes) | Complete surgical excision with 4–6 mm margins; higher metastatic potential than BCC, particularly on lips, ears, or perineum |
| Malignant Melanoma | ABCDE criteria: Asymmetry, Border irregularity, Color variegation, Diameter > 6 mm, Evolution; BRAF V600E mutation common | Atypical melanocytes with hyperchromatic nuclei nesting along dermal-epidermal junction; S100 and Melan-A positive | Excisional biopsy with narrow 1–3 mm margins (avoid punch/shave); Wide local excision based on Breslow depth ± Sentinel lymph node biopsy |
Cellulitis vs. Erysipelas vs. Necrotizing Fasciitis
| Infection | Depth of Tissue & Primary Pathogens | Key Differentiating Physical Findings | First-Line Antimicrobial / Surgical Intervention |
|---|---|---|---|
| Erysipelas | Upper dermis and superficial lymphatics; Group A Streptococcus (Streptococcus pyogenes) | Abrupt onset, bright fiery red, raised with sharply demarcated borders; facial or lower extremity predilection | Oral Penicillin VK or Amoxicillin; IV Cefazolin or Ceftriaxone if systemic signs |
| Non-Purulent Cellulitis | Deeper dermis and subcutaneous fat; Group A Strep > Staphylococcus aureus | Erythema, warmth, edema, tenderness with indistinct, poorly demarcated margins; constitutional fever | Oral Cephalexin or Cefazolin; elevate affected extremity to promote lymphatic drainage |
| Necrotizing Fasciitis | Fascial planes and subcutaneous soft tissues; Type I: Polymicrobial (enterics + anaerobes); Type II: Group A Strep alone (flesh-eating bacteria) | Pain out of proportion to physical exam, anesthesia over central area, bronze/purple bullae, crepitus, septic shock, elevated LRINEC score | Emergent surgical fasciotomy and radical debridement + IV broad-spectrum: Vancomycin + Piperacillin-tazobactam + Clindamycin (inhibits toxic shock exotoxins) |
OMM Board Correlate: Lymphatic Drainage in Lower Extremity Infections
- Contraindication in Active Infections: Effleurage, petrissage, and lymphatic pump techniques directly over acute bacterial cellulitis or erysipelas are STRICTLY CONTRAINDICATED due to the danger of hematogenous bacterial dissemination and septicemia.
- Central Release Only: Once systemic antimicrobial coverage is initiated, gentle passive treatment of central thoracic inlet (T1, 1st rib) and abdominal diaphragm crura (L1–L3) helps clear systemic edema without disturbing the localized limb nidus.
Board Traps & Common Distractors
- Pain out of proportion to exam or soft tissue crepitus on palpation is Necrotizing Fasciitis until proven otherwise; NEVER delay emergent surgical exploration for imaging or laboratory workup.
- Shave biopsy of a pigmented lesion suspicious for melanoma is contraindicated; full-thickness excisional biopsy with 1–3 mm margins is required to accurately assess Breslow depth for staging.
- Clindamycin must always be added to beta-lactams in severe Group A Streptococcal necrotizing fasciitis or toxic shock syndrome because it acts on bacterial ribosomes (50S subunit) to halt M-protein and pyrogenic exotoxin production.