Which of the following is the most common histological subtype of basal cell carcinoma encountered in routine dermatopathology practice?

Explanation

## Most Common Histological Subtype of BCC **Key Point:** **Nodular BCC** is the most common histological subtype, accounting for 60–80% of all BCC cases. It is characterized by well-circumscribed nests of basaloid cells in the dermis with peripheral palisading and mucin deposition. ### Histological Subtypes and Frequency | Subtype | Frequency | Key Features | Prognosis | | --- | --- | --- | --- | | **Nodular** | 60–80% | Well-circumscribed nests, peripheral palisading, mucin, pearly nodule clinically | Excellent, low recurrence | | Superficial | 15–25% | Buds connected to epidermis, multifocal, erythematous patches | Good, responds to topical therapy | | Infiltrative/Morpheaform | 5–10% | Thin strands, fibrosis, ill-defined borders, scar-like | Poor, higher recurrence, aggressive | | Basosquamous | 1–3% | Mixed basaloid + squamous differentiation, high mitotic rate | Poor, aggressive, higher recurrence | ### Clinical Correlation **High-Yield:** Nodular BCC typically presents as a **pearly, translucent nodule** with **arborizing (branching) vessels** on dermoscopy and often shows **central ulceration** (rodent ulcer). This is the classic teaching presentation. **Clinical Pearl:** The histological subtype does NOT always correlate with clinical appearance. A clinically nodular lesion may show superficial, infiltrative, or mixed histology on biopsy. However, nodular is by far the most common. **Mnemonic:** **SNIB** = Superficial, Nodular, Infiltrative, Basosquamous (in order of frequency, with Nodular most common). ### Why Nodular is Most Common 1. **Pathogenesis** — arises from basal layer of epidermis in sun-exposed areas with chronic UV damage 2. **Growth pattern** — well-demarcated, slow-growing, low-risk lesions that don't progress to aggressive subtypes 3. **Clinical detection** — pearly appearance and ulceration make it clinically obvious, so it is diagnosed earlier than infiltrative variants 4. **Genetics** — most nodular BCC arise from sporadic PTCH1 or TP53 mutations, not syndromic causes **Warning:** Do NOT confuse histological subtype with clinical presentation. A patient may have a clinically "nodular-looking" lesion that is histologically infiltrative (and thus has higher recurrence). Always correlate clinical and pathological findings.