Differential Diagnoses for a Painful, Enlarging, Discolored 1 cm Skin Nodule in a 71-Year-Old Woman
This presentation—a growing, discolored, painful nodule in an elderly patient—raises immediate concern for malignant melanoma, which must be excluded first through full-thickness excisional biopsy. 1
Primary Malignant Concerns
Melanoma (Highest Priority)
- The combination of recent growth, color change, and new-onset pain in a 1 cm lesion meets multiple criteria from the ABCDE rule (Asymmetry, Border irregularity, Color heterogeneity, Diameter >6 mm, Evolution of characteristics) 1
- Pain is an atypical but concerning feature that may indicate deeper invasion or ulceration 1
- At 71 years old, this patient falls within the high-risk age group for melanoma 1
- Melanoma can present as a nodular variant that grows rapidly and becomes symptomatic 2, 3
Basal Cell Carcinoma
- Common in elderly patients and can present as a growing nodule with color changes 4
- May become painful if ulcerated or inflamed 4
- Less aggressive than melanoma but requires excision 4
Squamous Cell Carcinoma
- Frequently occurs in elderly patients on sun-exposed or non-exposed skin 4, 5
- Can present as a painful, growing nodule, particularly when rapidly enlarging 4
- May arise from precursor lesions like actinic keratosis 4
Benign but Concerning Lesions
Keratoacanthoma
- Rapidly growing nodule that can mimic squamous cell carcinoma 4
- Typically grows over weeks to months and may become tender 4
- Requires biopsy to distinguish from malignancy 4
Inflamed or Infected Seborrheic Keratosis
- Common benign tumor in elderly patients that can become irritated, painful, and change in appearance 4
- However, any changing pigmented lesion requires biopsy to exclude melanoma 5
Infectious Etiologies (Lower Priority in This Context)
Atypical Mycobacterial or Fungal Infection
- Can present as painless-to-painful subcutaneous nodules in immunocompromised or elderly patients 1
- Less likely given the discoloration and growth pattern, but consider if the patient has immune deficiency 1
Nocardia
- Presents as subcutaneous nodules or abscesses, often painless initially 1
- More common in immunocompromised patients 1
Critical Next Steps
Perform a full-thickness excisional biopsy with a 2 mm margin of normal skin around the lesion immediately—partial or incisional biopsies are inadequate for pigmented lesions because they risk sampling error and cannot assess critical prognostic features like Breslow thickness 1, 6, 7
What to Document Before Biopsy:
- Exact size, shape, and color characteristics of the lesion 1
- Presence of asymmetry, border irregularity, or ulceration 1
- Duration and rate of growth 2
- Associated symptoms (pain, bleeding, itching) 1
Physical Examination Essentials:
- Complete full-body skin examination including scalp to identify additional suspicious lesions or second primary melanomas 8, 2
- Palpate all regional lymph node basins (axillary, cervical, inguinal depending on lesion location) to detect nodal metastases 8, 2, 3
Pathology Requirements:
The histopathology report must include 1:
- Confirmation of melanocytic nature and malignancy status
- Maximum tumor thickness in millimeters (Breslow depth)
- Level of invasion (Clark level)
- Presence or absence of ulceration
- Mitotic rate (for thin melanomas)
- Completeness of excision margins
Common Pitfalls to Avoid
- Never perform a shave or partial biopsy on a suspicious pigmented lesion—this prevents accurate Breslow depth measurement and can lead to understaging 6, 7
- Do not delay biopsy while observing a changing pigmented lesion in an elderly patient 5, 7
- Avoid frozen sections for pigmented lesions as they are inadequate for diagnosis 1
- Do not use laser or electrocoagulation for removal, as tissue destruction interferes with histologic assessment 2
- Do not assume pain indicates a benign process—melanoma can be painful, especially with ulceration or rapid growth 1