This special section of 6 articles includes the proceedings of the Seventh Princeton Integrated Pathology Symposium (PIPS): Bone, Soft Tissue and Hematologic Pathology, and other related reviews. The symposium was held virtually on Saturday, May 16, 2020. These reviews have numerous tables and figures, and may serve as a handy reference for your daily practice.

Beginning Part I, to commemorate the late Juan Rosai, MD, Garcia and DiCarlo review the clinical, radiologic, and pathologic features of Rosai-Dorfman disease of bone and soft tissue. The authors discuss its differential diagnosis, pathogenesis, and current management. The diagnostic hallmarks are emperipolesis and S100-positive histiocytes. However, bone and soft tissue lesions tend to have a small number of characteristic histiocytes, less conspicuous emperipolesis and areas of fibrosis or storiform spindle cells, and can become a diagnostic challenge. The authors summarize the markers and genomic profiles of Rosai-Dorfman disease versus its differential diagnoses in a table.

Advances in tumor genetics and markers propelled updates in the most recent edition of the World Health Organization classification of soft tissue and bone tumors. Wei and Siegal thus provide an overview on the current concepts of small round cell tumors of bone and soft tissue. They focus on salient histologic features, key immunophenotypic characteristics, and recent molecular genetic advancements of these small, round cell tumors. Several emerging entities are noteworthy for their unique molecular and clinical characteristics.

Similar to the small, round cell tumors, some lesions of bone and soft tissue were historically classified as reactive, but are recently considered as neoplasms. They are clinically aggressive and have reproducible molecular signatures. Thus, these “reactive” lesions should be best classified and treated as neoplasms. A timely update by Memon, Wei, and Siegal on the subject addresses these evolving lesions, and will help meet the diagnostic challenges of these “reactive” yet aggressive lesions. Of note, molecular typing is often required to accurately diagnose these lesions.

In Part II of this special section, we begin with the discussion of lymphoproliferative neoplasms with plasmablastic morphology that includes plasmablastic lymphoma, plasmablastic myeloma, primary effusion lymphoma, human herpesvirus 8–positive diffuse large B-cell lymphoma, and anaplastic lymphoma kinase–positive large B-cell lymphoma. They each have distinct morphologic and immunophenotypic characteristics. Here, Zhou and Nassiri not only thoroughly review the diagnostic criteria and tools, but provide a practical diagnostic algorithm for differentiating lymphoproliferative neoplasms with plasmablastic morphology.

Many lymphoma and virally transformed lymphoproliferative disorders are positive for cluster of differentiate 30 (CD30). Given the low expression of CD30 in normal tissue, CD30 has been a subject of developing targeted therapy for decades. Schwarting et al share their first-hand experiences and knowledge as early investigators on CD30, present diagnostic pearls of common CD30-positive neoplasms, and provide perspectives on targeted therapies of CD30-positive hematological malignancies. As a humanized anti-CD30 antibody, brentuximab vedotin was approved in 2012 for treating refractory Hodgkin lymphoma and anaplastic large cell lymphoma. Additional therapies based on chimeric antigen receptor–T cells targeting CD30 are on the horizon. These therapies are also reviewed with updates from recent clinical trials.

COVID-19 caused unprecedented socioeconomic and healthcare burdens throughout the world. Most COVID-19 research was focused on its impact on respiratory, cardiovascular, and coagulation systems. However, the hematologic complications of COVID-19 remain poorly understood. Because HIV and other viral pandemics have been associated with severe hematologic complications, the lessons learned from HIV and other viral pandemics may help us better understand those of COVID-19. Therefore, Karcher thoroughly reviews the hematologic complications of HIV and respiratory pandemics, including early data on those of COVID-19. The emerging knowledge in the hematologic complications of HIV, COVID-19, and other viral pandemics will greatly promote prevention, diagnosis, and treatment of hematologic complications in the future.

We are grateful to former Archives Interim Editor-in-Chief, Donna Hansel, MD, PhD, and current Editor-in-Chief Alain Borczuk, MD, the other advisory committee members of the PIPS, the authors, and the reviewers. We also wish to thank Patrick Kearns, Katie Giesen, and Hilary Price at the Archives editorial office, James Demetriades, MBA, and Elliot A. Krauss, MD, at Princeton Medical Center, and F. Michael Walsh, MD, MBA, at Aurora Diagnostics. Without them, this special section would not be possible.

Author notes

The author has no relevant financial interest in the products or companies described in this article.