The additional diagnostic value of optical coherence tomography in clinically diagnosed basal cell carcinomas undergoing direct surgical excision
Authors: F. Adan, P.J. Nelemans, N.W.J. Kelleners‐Smeets, J.P.H.M. Kessels, T. Brinkhuizen, K. Mosterd
Journal: British Journal of Dermatology (2021)

Dear Editor, Clinical examination appears to be very sensitive for diagnosing basal cell carcinoma (BCC) (90%), but the specificity is reported to be low (28·6–48·9%).1, 2 Additional use of dermoscopy can increase specificity to 54·3–55·6% compared with clinical examination alone.1, 2 With use of optical coherence tomography (OCT), a noninvasive diagnostic method, in addition to clinical and dermoscopic examination, it is possible to further increase the specificity to 76% at a sensitivity of 95%.1, 3, 4 These results apply to a population of patients with a clinical suspicion of BCC who had an indication for biopsy (e.g. high-risk location or uncertainty about diagnosis). However, there are subgroups of patients, such as patients with a very high clinical suspicion for a low-risk BCC or patients with multiple BCCs, who undergo direct surgical excision without prior histopathological verification of BCC diagnosis.5, 6 The aim of this study was to investigate whether OCT has additional diagnostic value in these subgroups of patients and whether it can help to reduce the risk of misclassification of non-BCC lesions as BCC. Patients were included from August 2019 to January 2021 in one academic hospital and two general hospitals in the Netherlands. The study was approved by the local ethics committee and was conducted in accordance with the Declaration of Helsinki. Written informed consent was obtained from all patients. All included lesions were highly suspicious for BCC based on clinical and dermoscopic examination and were scheduled for surgical excision without prior histopathological verification. Before surgery, an OCT scan was obtained for study purposes and the OCT diagnosis did not influence the treatment decision. A commercially available OCT device (< 7·5 μm lateral and < 5 μm axial optical resolution) was used for imaging (VivoSight, Michelson Diagnostics Ltd., Maidstone, UK). Analysis of OCT images was performed by one experienced observer using the morphological characteristics of BCC as previously described.7 Histopathological diagnosis was used as the gold standard. In total, 114 patients with a high clinical and dermoscopic suspicion of BCC were included; 59 (51·8%) in an academic hospital and 55 (48·2%) in general hospitals. The median age was 71 years (21–91) and 63 patients were male (55·3%). Lesions were located on the trunk (47·4%), head or neck area (35·1%) and extremities (17·5%). The results with respect to diagnostic accuracy of OCT are summarized in Table 1. According to histopathological diagnosis, 109 of 114 lesions were BCCs, which corresponds to a positive predictive value (PPV) of 95·6% for clinical and dermoscopic diagnosis. All 109 histopathologically verified BCCs were identified as such by OCT (sensitivity 100%) and the negative predictive value in cases with a negative OCT result was 100% (four of four). In only five of 114 lesions (4·4%) histopathology revealed an alternative diagnosis, i.e. seborrhoeic keratosis, solar elastosis, benign lichenoid keratosis, warty dyskeratoma and squamous cell carcinoma (SCC). OCT identified four of these five lesions as non-BCC lesions. A benign lichenoid keratosis was misclassified as BCC by both clinical and dermoscopic examination and OCT. Furthermore, the SCC was excised with a 3-mm margin and was radically removed. The majority (97·4%) of the lesions in this study, all scheduled for excision, were diagnosed as nodular BCCs according to clinical and dermoscopic findings. There were only three superficial BCCs, as noninvasive treatment is usually preferred in superficial BCC. Of all 109 BCCs, 11 (10·1%) were superficial, 81 (74·3%) were nodular and 17 (15·6%) were found to be infiltrative upon histopathology. Clinical and dermoscopic examination misclassified eight of 11 (72.7%) superficial BCCs as nodular, whereas with OCT seven of 11 (63.6%) were misclassified as mixed superficial/nodular BCC. In total, 17 (100%) infiltrative BCCs were misclassified as nodular by clinical and dermoscopic examination and 14 (82.4%) were misclassified by OCT. With additional use of OCT, the PPV increased from 95·6% (without OCT) to 99·2% (109 of 110) with OCT. The decrease in the percentage of misclassifications was not significant, but a study with enough power to detect differences in this order of magnitude would require a much larger sample size. In another prospective study, the PPV of an OCT diagnosis that was made with high confidence was only 80%, but the BCC prevalence in that study was also lower (58·2%) than in the present study (95·6%). The PPV depends on prevalence and becomes lower if prevalence decreases.8 The use of OCT in addition to clinical and dermoscopic examination may reduce the risk of misclassification of non-BCC lesions as BCC; however, this study also shows that in cases of high clinical and dermoscopic suspicion of BCC, this risk is already very low. The gain from additional use of OCT in patients with high clinical suspicion of BCC must be balanced against the financial investment required for the purchase of an OCT device and training of OCT users. We would like to thank pathologist Robert Riedl for his contribution to the manuscript. Fieke Adan: Conceptualization (equal); Formal analysis (lead); Investigation (lead); Methodology (equal); Project administration (lead); Validation (equal); Visualization (lead); Writing-original draft (lead); Writing-review & editing (equal). Patty Nelemans: Conceptualization (equal); Formal analysis (lead); Investigation (equal); Methodology (lead); Supervision (equal); Validation (equal); Writing-original draft (equal); Writing-review & editing (equal). Nicole WJ Kelleners-Smeets: Conceptualization (equal); Investigation (equal); Methodology (equal); Supervision (equal); Validation (equal); Writing-original draft (equal); Writing-review & editing (equal). Janneke Kessels : Conceptualization (equal); Investigation (equal); Methodology (equal); Supervision (equal); Validation (equal); Writing-review & editing (equal). Tjinta Brinkhuizen: Conceptualization (equal); Investigation (equal); Methodology (equal); Supervision (equal); Validation (equal); Writing-review & editing (equal). Klara Mosterd: Conceptualization (equal); Formal analysis (equal); Investigation (equal); Methodology (equal); Supervision (equal); Validation (equal); Visualization (equal); Writing-original draft (equal); Writing-review & editing (equal).