Cerroni, Lorenzo

Lymphomatoid papulosis (LyP) has several histopathologic presentations. LyP featuring gamma-delta (γδ) T-cell receptor expression may masquerade as and may be misdiagnosed as aggressive cutaneous T-cell lymphoma, particularly primary cutaneous γδ T-cell lymphoma (PCGDTL) or γδ mycosis fungoides. We performed a clinicopathologic analysis of the largest series of LyP featuring γδ T-cell expression. We identified 26 patients with a diagnosis of LyP with γδ T cells from our institutions, as well as through a comprehensive review of the literature, and characterized these cases. Most cases were treated with topical steroids or not treated at all. The majority of cases showed a CD4-CD8+ phenotype and featured at least one cytotoxic marker. Histopathologic features included an intraepidermal or dermal infiltrate with large cells and frequent angiotropism. One case was initially misdiagnosed as PCGDTL, requiring further therapy. Our case series, the largest international cohort of γδ T cell predominant LyP cases, confirms marked clinicopathologic heterogeneity that may contribute to misdiagnosis, reasserting the need to identify classic clinical features, CD30+ T-cell components, and markers of cytotoxicity when dealing with this differential diagnosis. A limitation of this study includes somewhat limited follow-up, histologic, and immunophenotypic information for some cases.

Abstract Since the publication of the Revised European-American Classification of Lymphoid Neoplasms in 1994, subsequent updates of the classification of lymphoid neoplasms have been generated through iterative international efforts to achieve broad consensus among hematopathologists, geneticists, molecular scientists, and clinicians. Significant progress has recently been made in the characterization of malignancies of the immune system, with many new insights provided by genomic studies. They have led to this proposal. We have followed the same process that was successfully used for the third and fourth editions of the World Health Organization Classification of Hematologic Neoplasms. The definition, recommended studies, and criteria for the diagnosis of many entities have been extensively refined. Some categories considered provisional have now been upgraded to definite entities. Terminology for some diseases has been revised to adapt nomenclature to the current knowledge of their biology, but these modifications have been restricted to well-justified situations. Major findings from recent genomic studies have impacted the conceptual framework and diagnostic criteria for many disease entities. These changes will have an impact on optimal clinical management. The conclusions of this work are summarized in this report as the proposed International Consensus Classification of mature lymphoid, histiocytic, and dendritic cell tumors.

This pathology PILOT study aims to define the role and feasibility of centralized pathology review in a cohort of 75 patients from different centers in the United States and Europe using digital slide scanning. The pathologic material from 75 patients who had been diagnosed with mycosis fungoides/Sézary syndrome and were clinically staged as IIb or above was retrieved from 11 participating centers. Each pathology reviewer was provided with the pathologic diagnosis (by the referring pathologist), and the following list of histopathologic criteria (presence or absence) from the initial report: epidermotropism, folliculotropism (FT), large cell transformation, syringotropism, and granulomas. Patients with advance stage were selected for this study as this is a population where there is significant variability in the diagnosis of pathologic prognostic and predictive biomarkers. The slides were digitally scanned with an Aperio scanner and consensus review of cases occurred when major or minor discrepancies between the referral diagnosis and central pathology review occurred. Among the 75 cases, 70 (93.3%) had a final consensus diagnosis between the 3 central review pathologists. The overall agreement between the consensus review and the referring pathologist was 60%. The overall agreement was also higher between the reviewers and consensus review, compared with the referring pathologist and consensus. 65.3% of cases had some type of discrepancy (major or minor) between the outside and consensus review. Major discrepancies were seen in 34 of 73 cases (46.6%; 73 cases indicated a yes or no response). Minor discrepancies were seen in 32 of 75 (42.7%) of cases. Most of the major discrepancies were accounted by a difference in interpretation in the presence or absence of large cell transformation or FT. Most minor discrepancies were explained by a different interpretation in the expression of CD30. We found digital slide scanning to be a beneficial, reliable, and practical for a methodical approach to perform central pathology review in the context of a large clinical prospective study.