A 72-year-old woman from Mumbai with a history of chronic sun exposure presents with multiple small, flesh-colored to translucent papules on her forehead and cheeks that have been present for 2 years. She reports that they occasionally bleed with minor trauma. On dermoscopy, multiple lesions show a homogeneous pattern with fine telangiectasia and no pigmentation. A biopsy of one lesion shows nests of basaloid cells with peripheral palisading and retraction artifact. Which histological variant of basal cell carcinoma is most likely?

Explanation

## Histological Diagnosis: Nodular Basal Cell Carcinoma ### Clinical-Histological Correlation **Key Point:** The biopsy description — **nests of basaloid cells with peripheral palisading and retraction artifact** — is the classic histological hallmark of **nodular BCC**, the most common variant (~60–80% of all BCCs). Superficial BCC, by contrast, shows thin buds or strands of basaloid cells attached to the undersurface of the epidermis, confined to the papillary dermis, without forming large discrete nests. ### BCC Histological Variants: Comparative Table | Variant | Clinical Presentation | Histology | Key Distinguishing Feature | | --- | --- | --- | --- | | **Nodular** | Pearly/translucent papule or nodule, telangiectasia, bleeds easily | Large nests of basaloid cells in dermis, peripheral palisading, retraction artifact | Most common; large discrete nests | | **Superficial** | Erythematous scaly patch/plaque, trunk > face | Thin buds attached to epidermis, confined to papillary dermis | No large nests; epidermal attachment | | **Infiltrative** | Ill-defined, scar-like plaque | Thin strands infiltrating dermis, perineural invasion | Aggressive; no palisading | | **Basosquamous** | Aggressive nodule | Mixed basaloid + squamous differentiation | Metastatic potential | **High-Yield:** Peripheral palisading + retraction artifact in **large nests** = Nodular BCC. Superficial BCC does NOT form large nests; it shows thin epidermal buds/strands limited to the superficial dermis. ### Histopathological Features of Nodular BCC 1. **Large nests of basaloid cells** extending into the dermis 2. **Peripheral palisading** of nuclei at the tumor-stroma interface 3. **Retraction artifact** (clefting) between tumor nests and stroma — due to mucin dissolution during processing 4. **Scant cytoplasm**, hyperchromatic nuclei, minimal mitoses 5. **Mucinous stroma** surrounding nests 6. **No squamous differentiation** (distinguishes from basosquamous carcinoma) **Clinical Pearl:** Nodular BCC classically presents as a **pearly/translucent papule or nodule** with **rolled borders** and **arborizing telangiectasia** on the face of elderly patients with chronic sun exposure — exactly as described in this vignette. Multiple small nodular BCCs can occur in the same patient. ### Why Nodular BCC and NOT Superficial BCC? - **Histology is decisive**: The question explicitly states "nests of basaloid cells with peripheral palisading and retraction artifact." This describes **nodular BCC**. Superficial BCC shows thin epidermal buds/strands, NOT discrete nests. - **Translucent papules with telangiectasia** → classic for nodular BCC (the "pearly" quality comes from the large nests visible through thin epidermis) - **Bleeding with minor trauma** → fragile telangiectatic vessels overlying nodular nests - **Dermoscopy: homogeneous pattern + fine telangiectasia** → consistent with nodular BCC (arborizing vessels are characteristic) - Superficial BCC typically presents as **flat erythematous patches/plaques**, more common on the trunk, with a different dermoscopic pattern (superficial fine telangiectasia + shiny white areas) ### Why the Original Answer (Superficial BCC) Was Incorrect Superficial BCC histology shows **thin strands or buds of basaloid cells budding from the epidermis**, confined to the papillary dermis — it does **not** form the large discrete nests described in the stem. The presence of "nests" with peripheral palisading is definitional for nodular BCC (Lever's Histopathology of the Skin, 11e; Robbins & Cotran Pathologic Basis of Disease, 10e, Ch. 25). **Mnemonic:** **NESTS = Nodular BCC** — **N**ests, **E**pidermis-independent, **S**troma retraction, **T**elangiectasia, **S**un-exposed face. [cite: Robbins & Cotran 10e Ch 25; Lever's Histopathology of the Skin 11e]