Dogliotti and Phillips classifications are unsuitable for grading the histopathological findings of exogenous ochronosis

Background: Cutaneous exogenous ochronosis (EO) is frequently graded and staged according to the Dogliotti or Phillips classification system, in both research studies and in clinical practice. There are no data to support the use of these systems in either of these settings. These systems additionally purport that the clinical and histopathological findings of EO are concordant, however, anecdotal evidence suggests otherwise. We aimed to determine the clinical-histopathological concordance rates in EO and to assess the suitability of the Dogliotti and Phillips classification systems for the grading and staging of EO lesions. Methods: Five cutaneous EO cases diagnosed at our institution were studied. Clinical and histopathological data were obtained by medical record and histopathology slide review. Each case was assigned a clinical and histopathological grade according to both the Dogliotti and Phillips classifications. Clinical-histopathological concordance rates were determined for each classification. Results: Clinical-histopathological concordance was seen in 80% and 60% of EO lesions when graded according to the Dogliotti and Phillips classifications, respectively. Conclusions: Cutaneous EO lesions do not consistently show clinical-histopathological concordance. Although the Dogliotti and Phillips classifications may have clinical utility, they are not suitable to grade EO histopathologically.