HISTIOCYTOID SWEET SYNDROME VERSUS MYELODYPLASIA CUTIS: ΑΝ UNUSUAL CASE PRESENTATION

Summary: Histiocytoid Sweet syndrome (HSS) is a rare variant of Sweet syndrome (SS). HSS demonstrates papillary dermal edema with immature myeloid cells that resembled histiocytes rather than the neutrophils seen in SS. Recently, a new category of myeloid dermatosis has been proposed, called myelodysplasia cutis (MDS-cutis), describing the specific skin infiltration by myelodysplastic cells in patients with myelodysplastic syndrome (MDS). We report a case of a 75-year-old male with MDS presenting with a 4-5 cm erythematous lesion on his right chest wall. Punch biopsy revealed a dense dermal mixed infiltrate containing “histiocytoid” mononuclear cells with papillary dermal edema. The histiocytoid mononuclear cells were positive for MPO, CD33 and CD68 and negative for CD34 and CD117, supporting HSS. FISH/molecular studies performed on skin were positive for deletion 5q and 7q, and a TP53 mutation, similar to bone marrow (BM) studies. This case emphasizes a possible new category of myeloid dermatosis, MDS-cutis, uniquely presenting in a MDS patient with biallelic TP53 inactivation. HSS occurring in the context of MDS is better considered MDS-cutis to describe skin infiltration of myelodysplastic cells. Patients with the same clonal origin of myeloid cells present in the BM and the skin, suggests MDS-cutis as a true entity.