As a primary care physician, how should I manage a female patient with a one‑week history of a red, crusted vulvar lump (originating from a rash on the side of the vagina) who is already receiving ceftriaxone for a shoulder infection?

Immediate Clinical Assessment and Biopsy Required

You must perform a vulvar punch biopsy immediately to establish a definitive diagnosis, as this red, crusted vulvar lump persisting for one week could represent anything from a benign inflammatory dermatosis to a premalignant or malignant lesion. 1, 2

Why Biopsy is Critical Now

The clinical presentation—a rash that evolved into a red, crusted lump over one week—is non-specific and cannot be diagnosed by appearance alone. The differential diagnosis is broad and includes:

• Infectious causes: Secondary bacterial infection (impetigo, cellulitis), herpes simplex virus, fungal infection
• Inflammatory dermatoses: Contact dermatitis (irritant or allergic), psoriasis, lichen simplex chronicus, lichen sclerosus
• Premalignant/malignant lesions: Vulvar intraepithelial neoplasia (VIN), basal cell carcinoma, squamous cell carcinoma 3, 2, 4

Any persistent, pigmented, irritating, or expanding vulvar lesion should be biopsied regardless of patient age. 2 Delays in diagnosis of vulvar pathology average 2 years from initial presentation, which can lead to anatomical changes, malignant transformation, sexual dysfunction, and decreased quality of life. 3

The Ceftriaxone Issue

The patient is already receiving ceftriaxone for a shoulder infection. While ceftriaxone has broad-spectrum coverage, it does not adequately cover common vulvar skin pathogens if this is a secondary bacterial skin infection (e.g., Staphylococcus aureus, Streptococcus pyogenes). 5 Additionally, ceftriaxone can precipitate vulvovaginal candidiasis in some patients, though this typically presents with pruritus and white discharge rather than a red, crusted lump. 6

Immediate Management Algorithm

Step 1: Detailed Clinical History

• Symptom timeline: Exact progression from rash to lump
• Associated symptoms: Pruritus, pain, burning, dyspareunia, discharge, fever
• Product exposure: New soaps, detergents, lubricants, topical medications, hygiene products (common allergens/irritants) 7, 8
• Sexual history: New partners, STI risk factors, condom use
• Medical history: Immunosuppression, diabetes, previous vulvar conditions, autoimmune diseases
• Medication history: Recent antibiotics (can trigger candidiasis), topical steroids

Step 2: Systematic Vulvar Examination

• Inspect all vulvar structures: Labia majora, labia minora, clitoris, vestibule, perineum, perianal area 9, 7
• Document lesion characteristics:
  • Size, shape, borders (well-demarcated vs. irregular)
  • Color (erythematous, hyperpigmented, white)
  • Surface texture (crusted, ulcerated, verrucous, smooth)
  • Single vs. multiple lesions
  • Palpate for induration, tenderness, fluctuance
• Check for lymphadenopathy: Inguinal nodes
• Examine vagina and cervix: Rule out concurrent infections or lesions

Step 3: Perform Vulvar Punch Biopsy

Indications for immediate biopsy (this patient meets criteria):

• Persistent lesion >2-4 weeks despite conservative management
• Lesion with concerning features (crusting, induration, irregular borders, pigmentation changes)
• Uncertain diagnosis
• Failure to respond to empiric treatment 1, 2, 7

Biopsy technique:

• Use 4-6mm punch biopsy tool
• Local anesthesia with 1% lidocaine with epinephrine
• Biopsy from most abnormal-appearing area, including edge if ulcerated
• Include dermis and subcutaneous tissue
• Send for routine histopathology; consider additional tissue for culture if infection suspected 1

Step 4: Obtain Ancillary Tests

• Bacterial culture and sensitivity: Swab from lesion surface if infection suspected
• HSV PCR: If vesicular component or history suggests herpes
• Fungal culture: If candidiasis suspected (though presentation atypical)
• STI screening: Consider gonorrhea/chlamydia testing, syphilis serology, HIV testing 10, 11

Step 5: Empiric Treatment While Awaiting Biopsy Results

Do NOT start empiric treatment before biopsy unless there is evidence of acute bacterial infection with systemic symptoms (fever, rapidly spreading erythema, lymphangitis).

If acute bacterial superinfection is suspected based on:

• Purulent drainage
• Rapidly expanding erythema
• Warmth, tenderness
• Systemic symptoms

Then add targeted antibiotic coverage:

• Cephalexin 500mg PO QID for 7-10 days (covers Staph/Strep skin flora)
• OR Doxycycline 100mg PO BID for 7-10 days (alternative if beta-lactam allergy)

The current ceftriaxone for shoulder infection is not adequate for vulvar skin infection and should not be relied upon. 5

Common Pitfalls to Avoid

1. Assuming it's "just yeast": Red, crusted lesions are not typical for candidiasis, which usually presents with pruritus, white discharge, and normal vulvar pH <4.5. 11, 6

2. Delaying biopsy: Waiting to see if lesions resolve with empiric treatment delays diagnosis of potentially serious conditions. 3, 2

3. Treating empirically without diagnosis: This can mask underlying pathology and delay appropriate management.

4. Overlooking contact dermatitis: Many vulvar complaints are due to irritant or allergic contact dermatitis from hygiene products, detergents, or topical medications. 7, 8

5. Inadequate examination: Failing to visualize the entire vulva, vagina, and cervix can miss concurrent pathology.

Follow-Up Plan

• Biopsy results: Review within 5-7 days
• Culture results: Review within 48-72 hours if obtained
• Adjust treatment based on histopathology and culture results
• Refer to gynecology or dermatology if biopsy shows:
  • Premalignant lesions (VIN)
  • Malignancy
  • Complex inflammatory dermatoses requiring specialized management (e.g., lichen sclerosus, erosive lichen planus)
  • Lesions not responding to appropriate treatment 3, 7

The key message: Biopsy now, treat based on results, not assumptions.