How to recognize a difficult squamous cell carcinoma? A retrospective analysis of clinically and dermatoscopically misdiagnosed tumors.

Abstract

Background: Squamous cell carcinoma (SCC) is usually non-pigmented in fair-skinned individuals and has to be discriminated from other non-pigmented tumors. Although the dermatoscopic features of SCC are well-known, some SCCs are challenging to recognize even with dermatoscopy.

Objectives: To investigate clinical and dermatoscopic features responsible for an inaccurate clinical diagnosis of invasive SCC and potential clues that could help in their recognition.

Methods: Retrospectively screening our institutional database, we screened for clinically misdiagnosed SCCs within a time period of 10 years (2013 to 2023). 10 expert dermatoscopists were presented a series of clinical and dermatoscopic images of misdiagnosed invasive SCCs.

Results: Seventy-three SCCs from 73 patients (55 males and 18 females) aged 37 to 97 years old (mean age 78.8 years) were included. Most tumors were located on the cheek (20,5%), followed by forehead (16,4%), nose (12,32%) and scalp (12,32%). Thirty-seven SCCs were misdiagnosed as BCC, 15 as actinic keratosis, 10 as irritated seborrheic keratosis, 7 as Bowen disease, 2 as viral wart and 2 as cutaneous horn. White scales and keratin were voted as the main features that might have helped in the accurate clinical diagnosis of the included SCCs (29/73).

Conclusions: The dermatoscopic characteristics of invasive SCC might overlap with other tumors. In challenging tumors, white scale and keratin might guide the accurate recognition of invasive SCC.