What are aging brown skin lesions that can become large, elevated, and crusted?

Aging Brown Skin Lesions: Seborrheic Keratoses

The aging brown lesions you're describing are most likely seborrheic keratoses (SK), which are the most common benign epidermal tumors in elderly patients and characteristically can become large, elevated, and crusted. 1, 2

Clinical Characteristics

Seborrheic keratoses present with the following features:

• Appearance: Brown to black, oval-shaped lesions with a characteristic "stuck-on" appearance 3
• Size: Range from a few millimeters to several centimeters, and can reach pendulous proportions in areas of constant friction, especially in obese individuals 4
• Texture: Can become elevated, crusted, and develop a warty or rough surface 1
• Common locations: Face, scalp, upper trunk, chest, and back (palms and soles are spared) 1

Critical Differential Diagnosis

While seborrheic keratoses are benign, they can mimic melanoma and other malignant lesions, making accurate diagnosis essential for patient safety. 5, 6

The key concern is distinguishing SK from:

• Melanoma: Pigmented and inflamed SK may closely resemble melanoma and lack typical dermoscopic features 6
• Pigmented basal cell carcinoma 5
• Pigmented actinic keratosis 6

When to Refer or Biopsy

Any pigmented lesion with one or more of the following major signs requires referral or excision: 7

Major Warning Signs:

• Change in size 7
• Change in shape 7
• Change in color 7

Minor Warning Signs (strengthen referral indication):

• Inflammation 7
• Crusting or bleeding 7
• Sensory change 7
• Diameter ≥ 7 mm 7

Diagnostic Approach

For any melanocytic lesion thought to be malignant, complete excision with a narrow rim (2 mm) of normal skin is the standard practice rather than partial biopsy. 5, 7

The rationale for complete excision includes:

• Risk of misdiagnosis if only partially examined 7
• Need to assess all histological parameters, particularly maximum thickness 7
• If benign, no further treatment needed 7

All skin lesions that cannot be classified as clearly benign should undergo biopsy. 6

Common Pitfalls

• Pigmented and inflamed SK does not usually show typical dermoscopic features and may mimic melanoma 6
• Dermoscopy can help differentiate SK from melanoma, but in equivocal cases, accurate diagnosis can only be made by histopathology 6
• Dermatoscopy should only be used by those familiar with the technique, as accuracy depends on experience 7
• Never use laser or electro-coagulation for initial excision of suspicious lesions, as tissue destruction compromises diagnosis 7

Treatment Considerations

For confirmed benign seborrheic keratoses, treatment options include 1:

• Surgical excision
• Cryotherapy
• Electrocautery
• Laser therapy
• Topical drug therapy (currently in development)

However, there is no medical indication for removal—treatment is purely for cosmetic reasons and should be based on patient preference. 1