BCC Ovoid Nests — SCE Dermatology MCQ

Correct answer: B — Blue-grey ovoid nests — clusters of basaloid tumour cells with melanin in the dermis; one of the most specific dermoscopic features of BCC

The correct answer is B, blue-grey ovoid nests, described as clusters of basaloid tumour cells with melanin in the dermis and one of the most specific dermoscopic features of BCC. These are large, well-circumscribed, confluent pigmented structures larger than simple globules, corresponding histologically to tumour islands containing melanin within the dermis. Their presence, in the absence of a pigment network, is a core positive criterion in the two-step dermoscopy algorithm used to diagnose pigmented BCC. The stem specifically describes multiple blue-grey globules scattered throughout a BCC lesion, which dermoscopedia and UK teaching resources classify as ovoid nests when large and confluent, distinguishing them from melanocytic pigment patterns. Why the other options are wrong: E. Comedo-like openings: these are keratin-filled follicular plugs seen in seborrhoeic keratosis, not a recognised BCC criterion. A. Lacunae: these are red-blue to red-black round to oval lacunar structures characteristic of vascular lesions such as haemangiomas, reflecting blood-filled dermal spaces, not basaloid tumour nests. D. Milia-like cysts: these are small white or yellow round structures from keratin-filled epidermal cysts, classically seen in seborrhoeic keratosis (and occasionally papillomatous melanocytic naevi), not specific to BCC. C. Chrysalis structures: these are white, shiny, orthogonal crystalline lines seen only under polarised dermoscopy, associated with dermatofibroma and some melanomas, arising from collagen birefringence rather than pigmented tumour islands. Key point: large, well-circumscribed blue-grey ovoid nests, representing dermal basaloid tumour islands with melanin and occurring alongside absence of a pigment network, are among the most specific dermoscopic clues to pigmented BCC.

Reference: DermNet NZ, Basal cell carcinoma dermoscopy, https://dermnetnz.org/topics/basal-cell-carcinoma-dermoscopy