Pyoderma gangrenosum with myeloperoxidase-positive histiocytoid cells

Pyoderma gangrenosum (PG) is a neutrophilic dermatosis, typically presenting as painful ulcers. This article reports a unique case of genital PG in a 72-year-old female with myelodysplastic syndrome. The histopathological examination revealed an unusual histiocytic infiltration. Immunohistochemistry showed the positivity of myeloperoxidase positivity along with CD68 positivity. Notably, while histiocytoid Sweet’s syndrome is recognized as a distinct pathological entity, no such classification exists for PG with a histiocytoid predominant infiltrate. Currently, the presence of a neutrophilic infiltrate is a primary criterion for diagnosing PG. These findings highlight the need for revised diagnostic criteria to account for the variability in histopathological presentations of PG and to prevent misdiagnosis.