Diagnostic pitfalls: how availability and anchoring biases lead to errors in dermatology

OBJECTIVES: We will explore the diagnostic similarities of spindle cell neoplasms and the attributed heuristics that lead to misdiagnosis biases. The biases explored will include availability bias and anchoring bias, with a discussion on the events leading to their formation. CASE PRESENTATION: A 58-year-old African American male with a past medical history of well-controlled HIV presented to the dermatology clinic for a two-year history of several persistent skin nodules on his lower legs. One lesion on his left lateral calf, a 1.5 cm dome-shaped nodule with a centralized keratinous plug, was suspicious for squamous cell carcinoma (SCC), prompting a shave biopsy. The dermatopathology report identified the lesion as dermatofibrosarcoma protuberans (DFSP) with CD34 positivity and the patient was referred for Mohs Micrographic Surgery. Frozen sections during Mohs surgery revealed concern for an alternative diagnosis, which was then confirmed as Kaposi Sarcoma. CONCLUSIONS: This case highlights the susceptibility of dermatology to misdiagnosis. Availability bias in the clinical setting led to an inadequate biopsy method. Further anchoring bias then potentially influenced histologic interpretation and management decisions. Insufficient appreciation of Kaposi Sarcoma development in the setting of well-controlled HIV also further influenced the diagnosis rendered. Mohs Surgery evaluation allowed for de-biased clinical and histologic assessment, correcting diagnosis. Several overlying factors, such as time pressures, knowledge gaps, and technique limitations, create a reliance on cognitive heuristics. Recognizing these external pressures can help clinicians enhance diagnostic accuracy by systematically considering alternative diagnoses.