The Spade Sign as a Pathognomonic Histopathologic Feature of Acne Keloidalis: Analysis of 33 Cases of Cicatricial Alopecia

The study analyzed 33 cases of cicatricial alopecia to evaluate the sensitivity and specificity of the "spade sign" (SS) and "balloon sign" (BS) in diagnosing acne keloidalis (AK), a form of primary cicatricial alopecia. The SS and BS are defined as a spade-shaped or round space created by the dilated and thinned follicular epithelium in the lower isthmus. The study found that the SS or BS was present in 33% of AK specimens and was not present in other forms of cicatricial alopecia. The sensitivity and specificity of the SS or BS for AK were found to be 33% and 100%, respectively. The study concluded that the SS or BS is a highly specific feature of AK, and while its absence does not argue against AK, its presence supports its diagnosis.