Plasmacytoid Dendritic Cell Dermatosis Associated to Myeloproliferative/Myelodysplastic Neoplasms

Abstract

Cutaneous lesions in the setting of myeloproliferative neoplasms and myelodysplastic syndromes are poorly understood. We report 6 patients with pruritic papular eruptions composed of mature T-lymphocytes with large clusters of CD123-positive cells. Double immunohistochemical studies demonstrated a lack of myeloid cell nuclear differentiation antigen in the CD123-positive cells, which expressed SPIB, confirming that they were mature plasmacytoid dendritic cells. Four patients were diagnosed with chronic myelomonocytic leukemia and 2 with myelodysplastic syndromes (AREB-I and myelodysplastic syndromes with 5q deletion, respectively). All patients had a long history of hematological alterations, mainly thrombocytopenia, preceding the cutaneous disorder. Nevertheless, the skin lesions developed in all cases coincidentally with either progression or full-establishment of their hematological disease. Most cutaneous lesions disappeared spontaneously or after corticosteroid treatment. Molecular studies performed in both bone marrow and cutaneous lesions in 2 patients demonstrated the same mutational profile, confirming the specific, neoplastic nature of these mature plasmacytoid dendritic cells-composed cutaneous lesions.

Plasmacytoid dendritic cells in the setting of myeloid neoplasms: Diagnostic guide to challenging pathologic presentations

“…Per the fifth edition of the World Health Organization (WHO) classification, 32 MPDCPs are defined as nodules of mature pDCs in the setting of myeloid neoplasms with absence or low/partial expression of CD56 in pDCs. MPDCPs may involve the bone marrow or extramedullary sites, such as the skin and lymph nodes 3,24,33–35 . The presence of extensive pDC nodules within tissues in the absence of an established haematologic disease should prompt further evaluation to exclude a myeloid neoplasm 33 …”

“…Skin involvement often presents as pruritic papular eruptions clinically. Histologically, the involvement is composed of clusters of mature pDCs surrounding vessels or adnexa in the upper dermis with admixed abundant mature T‐cells 34 …”

“…MPDCPs may involve the bone marrow or extramedullary sites, such as the skin and lymph nodes. 3,24,[33][34][35] The presence of extensive pDC nodules within tissues in the absence of an established haematologic disease should prompt further evaluation to exclude a myeloid neoplasm. 33 In the bone marrow (Figure 2), pDC nodules are interstitially located and composed of uniform pDCs, 3 morphologically similar to physiologic pDCs, reflecting the maturity of these nodules.…”

“…Histologically, the involvement is composed of clusters of mature pDCs surrounding vessels or adnexa in the upper dermis with admixed abundant mature T-cells. 34 In lymph nodes (Figure 3), pDC nodules can resemble reactive germinal centres given the frequent presence of apoptotic bodies (starry-sky pattern) and negative BCL2 expression by immunohistochemistry. Unlike reactive germinal centres, pDC nodules lack centrocytes and centroblasts, in addition, they lack mantle and marginal zones characteristic of secondary follicles.…”

“…Immunophenotypically, MPDCPs demonstrate an antigen profile similar to their 'mature' physiologic pDCs counterpart 17,19,21,22,34,35 : positivity for CD123, CD303, CD304 and TCL1, with negativity for CD34, CD56 and Terminal deoxynucleotidyl Transferase (TdT) expression; occasional expression of CD2, CD5, CD7, CD13, and CD33 may be encountered. 18,24,36 While CD56 expression is negative in most MPDCP, focal and weak reactivity may be observed, 18,37 as it is seen in a subset of physiologic pDCs.…”