SCC Dermoscopic Mimics

01Irritated seborrheic keratosis (ISK) is the most common SCC mimic in everyday clinical practice. Papageorgiou (JAAD 2021) compared 104 SCCs and 61 ISKs and identified discriminating features. SCC favors: dotted vessels (OR 10.4), branched linear vessels (OR 5.3), white structureless areas (OR 6.78), white circles around follicles (OR 23.45), peripheral or diffuse irregular vessel arrangement, central scale distribution. ISK favors: hairpin vessels (OR 0.38 for SCC, i.e., favors ISK), diffuse regular vessel arrangement (OR 0.39 for SCC), white halos around vessels covering >10 percent of lesion (OR 0.29 to 0.12 for SCC). The key gestalt: ISK is symmetric with diffuse regular hairpin vessels surrounded by multiple white halos; SCC is asymmetric with focal, polymorphic, often peripheral vessels and white circles around follicles.

02Erosive pustular dermatosis of the scalp (EPDS) is a chronic neutrophilic dermatosis of bald photodamaged scalp that mimics SCC clinically and even on biopsy if the sample is too superficial. Scharf (Dermatol Pract Concept 2025) compared 43 EPDS cases initially diagnosed as SCC with 43 confirmed scalp SCCs. EPDS favors: orange/salmon background (51 vs 0 percent in SCC, p<0.01), polymorphic vessels (49 vs 19 percent), branched vessels in EPDS (16 vs 0 percent in SCC), absence of vessels in some cases (16 percent of EPDS vs 0 percent of SCC), targetoid hair follicles/white circles (47 vs 24 percent). SCC favors: hairpin vessels (40 vs 0 percent), dotted vessels (36 vs 0 percent), white background (30 vs 0 percent), combined colors (39 vs 21 percent). Surprisingly, white circles were more common in EPDS than in SCC in this referral cohort, breaking the traditional rule. The orange/salmon background is the most specific EPDS clue.

03EPDS has a chronic relapsing course on bald scalp with persistent erosions, pustules, crusts, and scarring alopecia. It often follows trauma, cryotherapy, 5-FU, imiquimod, PDT, or laser. Differential includes multiple AKs, infiltrative SCC, and infected scalp. Treatment is high-potency topical corticosteroids, topical tacrolimus, oral tetracyclines, or oral steroids/dapsone for refractory disease. Prompt response to topical steroids supports the diagnosis.

04Hypertrophic discoid lupus erythematosus (DLE) on the face, ears, and scalp produces hyperkeratotic plaques with follicular plugging that mimic SCC and AK. Dermoscopic clues for DLE: keratotic follicular plugs (vs the open follicular ostia of SCC), white structureless areas, fine telangiectasia in a regular distribution, perifollicular whitish halos, follicular red dots, and absent or sparse polymorphic vessels. The clinical context (other DLE lesions, photosensitivity, ANA, oral ulcers) is critical. Hypertrophic DLE on the lip can mimic SCC and biopsy is mandatory because both can coexist (DLE-associated SCC) and DLE has a recognized SCC progression risk.

05Bowenoid papulosis is HPV-16-related multiple genital papules in younger sexually active patients. Histologically resembles Bowen's but generally has a more indolent course and may regress. Dermoscopically: brown structureless areas, irregular dotted/glomerular vessels in clusters, surface scale. Distinguishing from anogenital Bowen's and condyloma can be challenging; biopsy and HPV testing guide management. Unlike Bowen's, Bowenoid papulosis is usually treated less aggressively (cryotherapy, topical imiquimod) given its lower invasion risk.

06Lichen planus and lichen planus-like keratosis (LPLK) overlap with pigmented Bowen's and SCC. LPLK is the regressing phase of solar lentigo or seborrheic keratosis with lichenoid inflammation, often on chronically photodamaged skin. Dermoscopy: gray-brown granular pigment in fine annular distribution, pseudonetwork, sometimes residual lentigo features. Unlike Bowen's, LPLK lacks clustered glomerular vessels and white scale. Lichen planus proper shows Wickham striae (white reticular lines), purple-violaceous color, and well-defined polygonal papules.

07Eccrine poroma occurs on palms, soles, and rarely elsewhere. It can ulcerate and bleed, mimicking amelanotic melanoma, BCC, and SCC. Dermoscopy: pink to red lesion with characteristic 'frogspawn' vascular pattern (large clods of vascular structures), milky-red areas, white structureless areas. Vascular pattern can be polymorphic. Biopsy is required for definitive diagnosis. Malignant variant (porocarcinoma) is rare but locally aggressive.

08Other SCC mimics worth knowing: amelanotic melanoma (chaotic polymorphous vessels, milky-red areas, lack of keratin); Merkel cell carcinoma admixed with SCC (Suarez JAAD 2015 reported polymorphous vessels with milky-red areas, central scale, large-diameter arborizing vessels); pyogenic granuloma (collarette of scale, red lobules); chondrodermatitis nodularis helicis (tender white-yellow ulcer on antihelix in middle-aged men); deep fungal or atypical mycobacterial infections (pearly papules with central crust, can persist for years).

09Practical approach when an SCC mimic is suspected: (1) take a careful history (chronicity, prior trauma, immunosuppression, sexual history for genital lesions); (2) palpate (induration favors malignancy); (3) dermoscope with both polarized and non-polarized modes; (4) trial of topical corticosteroid or empiric anti-fungal/anti-bacterial only in low-risk locations and only if dermoscopy is reassuring; (5) biopsy with a deep specimen if anything is atypical, persistent beyond 4-6 weeks of empiric therapy, indurated, painful, or in a high-risk anatomic site.