Histiocytoid Sweet syndrome harboring an isocitrate dehydrogenase 1 mutation: A case report and retrospective analysis of 29 cases of histiocytoid Sweet syndrome

Abstract

Histiocytoid Sweet syndrome (HSS) is a rare histopathologic variant of Sweet syndrome that demonstrates dermal and/or subcutaneous infiltrate with a prominent component of myeloid cells resembling histiocytes. It has been known to occur in association with hematologic neoplasms, including myelodysplastic syndrome (MDS) and acute myelogenous leukemia, but whether it confers an increased risk of such neoplasms is controversial. Here, we describe a case of a HSS that led to the diagnosis of MDS with an isocitrate dehydrogenase 1 (IDH‐1) mutation and a corresponding study looking for additional cases of IDH‐1 mutations in biopsies of histiocytoid and conventional Sweet syndrome.

Differentiation syndrome during ivosidenib treatment with immunohistochemistry showing isocitrate dehydrogenase R132H mutation

“…In contrast to histiocytoid Sweet syndrome, in overt leukemia cutis, immature myeloblasts are present and can stain positive for CD34 and CD117 7 . Interestingly, histiocytoid Sweet syndrome harboring an IDH1 mutation has been previously reported, demonstrating a neutrophil‐rich infiltrate 8 . In contrast to this previously reported case, the infiltrate in our case was composed primarily of immature mononuclear cells compatible with blasts.…”

Neoplastic or inflammatory? A case report of Sweet syndrome with CD30+ cells in a patient with B‐lymphoblastic leukemia

“…The biopsy findings were also unique and demonstrated morphologic features of both variants of Sweet syndrome. Histopathologic variants of Sweet syndrome include the subcutaneous form with deeper involvement and histiocytoid Sweet syndrome that includes the presence of neutrophilic precursors with kidney‐shaped elongated nuclei resembling histiocytes 7 . Histiocytoid Sweet may also have the infiltrate extending into the subcutis, 8 similar to that seen in our case.…”

Sweet Syndrome Associated with Myelodysplastic Syndrome—A Review of a Multidisciplinary Approach

“…No biopsies of H-SS demonstrated purely subcutaneous infiltrates, although some cases did have an extension of the dermal infiltrate into the subcutis. Similarly, some of the conventional Sweet syndrome cases had at least minor involvement of the subcutis in addition to the dermis, but no cases had purely subcutaneous involvement [ 53 ].…”

“…It has been hypothesized that these lesions begin with the release of immature myeloid cells from the bone marrow in early stages, and these cells mature to neutrophils in later stages of the disease [ 53 ]. Histopathological differential diagnosis should be established with leukemia cutis [ 63 ] and other inflammatory conditions characterized by histiocytes interstitially arranged between collagen bundles of the dermis [ 52 , 54 , 61 ].…”

“…Libby et al [ 53 ] discuss a case of Histiocytoid Sweet syndrome, later diagnosed as MDS-EB1 with IDH-1 mutation. Background MDS was exposed with immunohistochemical stains for IDH-1, with positive markers on lungs and skin specimens.…”