Objective To establish dermatoscopic findings of clinically challenging FPSLs conforming PAK, SK, SL and LM and derive an Algorithm with diagnostic features for detecting Premalignant Facial Pigmented Skin Lesions. Methods We here in conducted a largest case study a cross sectional analysis of clinically challenging 182 flat FPSLs, evaluated dermoscopic images consistent to pigmented AK, early SK, SL and LM and subsequently biopsied for histopathological evidence. Four major dermoscopic features were appraised: pigment pattern, sharp demarcation, vascular criteria and follicular/epidermal pattern. Results We derived an Algorithm elucidating diagnostic findings of FPSLs. Pigmented AK on dermoscopy has strawberry pattern in 42% of lesions (pink to red pseudo-network with erythematous background, prominent follicular ostia fenced by a white targetoid halo), while Sharp demarcation (57.15%) and follicular/epidermal pattern (cerebriform pattern 100% of lesions, milialike cysts, 50%, and comedo-like openings 38.57%) are distinctively observed SK. In SL, homogenous structureless pigmentation is significant entirely (100%). However, in LM predominates pseudonetwork (89.47%), homogenous structureless pigmentation (78%) and vascular patterns while strawberry pattern is observed in (26.31%) of lesions. Conclusion Dermoscopy is extremely valuable tool for categorisation and diagnosis of different pigmented lesions on face. The patterns described and algorithms used are a perfect guideline for Dermatologists.