Pigmented Fibroepithelioma of Pinkus in Pregnancy: Strengths and Limitations of Reflectance Confocal Microscopy, Line‐Field Optical Coherence Tomography and Line‐Field Optical Coherence Tomography Artificial Intelligence Tool

Pigmented fibroepithelioma of Pinkus (FeP), a rare fibroepithelial variant of basal cell carcinoma (BCC), is clinically and dermoscopically challenging to diagnose and may mimic melanoma as well as benign lesions, such as sebhorreic keratosis. In pregnancy, a newly detected or progressively enlarging pigmented lesion raises additional diagnostic and management challenges, as timely and accurate classification must be balanced with maternal–foetal safety. A 31-year-old woman at 38 weeks' gestation presented with a slowly enlarging 5 × 7 mm translucent black–brown papule on the right abdominal flank. Dermoscopy showed a light-brown structureless background with patchy blue blotches, peripheral linear irregular/serpentine vessels and a central milia-like cyst/rosette under polarized light. Reflectance confocal microscopy (RCM) revealed, at higher magnification, epidermis-derived anastomosing basaloid cords with peripheral palisading and occasional clefting, with abundant plump bright cells in the stroma consistent with melanophages; these features were compatible with pigmented FeP and explained a deceptive low-magnification ‘ringed’ appearance. Line-field optical coherence tomography (LC-OCT) revealed epidermis-originating anastomosing cords surrounding hyper-reflective cell aggregates or hypo-reflective stroma. The device's embedded LC-OCT artificial intelligence classifier provided only focal ‘BCC-consistent’ outputs while labelling other areas as melanocytic, underscoring the need for critical, whole-lesion review. Given the third-trimester status and low-risk tumour behaviour, excision was deferred until postpartum. Histopathology confirmed pigmented FeP, with thin epithelial cords and strands arborizing in a collagenous stroma with ectatic vessels and superficial dermal melanin. Multimodal RCM and LC-OCT assessment revealed therefore useful and consistent, resolving diagnostic uncertainty in pregnancy and enabling individualized timing of surgery. Pigmented FeP may lack canonical LC-OCT patterns and may mislead low-magnification RCM or AI outputs; therefore, high-resolution assessment and cautious interpretation are essential.