Histologic and Immunohistochemical Features of Antemortem Thrombus Compared to Postmortem Clot: Updating the Definition of Lines of Zahn.

CONTEXT.­: Distinguishing true antemortem thrombus (AMT) from artifactual postmortem clot (PMC) can occasionally be challenging at autopsy. Lines of Zahn are cited as pathognomonic of AMT, but review of literature reveals heterogeneous definitions of the term. Neutrophil karyorrhexis and CD61 immunohistochemistry can also be used to define AMT, but there has been no systematic study determining the specificity of these features. OBJECTIVE.­: To identify features that distinguish AMT from PMC, and to clarify the definition of lines of Zahn. DESIGN.­: PMC from the heart was collected in 50 hospital autopsies. Fifty arterial and 50 venous surgical thrombectomy specimens were reviewed for comparison. The microscopic features with hematoxylin-eosin staining, phosphotungstic acid-hematoxylin (PTAH) staining, and CD61 immunohistochemistry were documented. RESULTS.­: Thin curvilinear strands of fibrin and clumps of fibrin were frequently observed in both AMT and PMC. Thick bands of nested platelets wrapped in fibrin were nearly exclusive to AMT. Neutrophil karyorrhexis was readily apparent on low power in AMT but was seen in 40 of 50 PMCs (80%) only sparsely on high-power examination. Bone marrow elements were identified in 38 of 50 PMCs (76%). CD61 staining showed a geographic pattern in AMT and a speckled pattern in PMC. PTAH staining confirmed features seen with hematoxylin-eosin. CONCLUSIONS.­: Thin curvilinear strands of fibrin are found in both AMT and PMC and can be misinterpreted as lines of Zahn. We define lines of Zahn as thick bands formed by nested platelets wrapped in fibrin. Diffuse neutrophil karyorrhexis is common in AMT; in contrast, bone marrow elements are often seen in PMC.

A Clinico-Pathologic Approach to the Differential Diagnosis of Pericardial Tumors.

PURPOSE OF REVIEW: Tumors of the pericardium are rare, but a wide variety of congenital, infectious, inflammatory, and neoplastic processes have been reported. Pericardial tumors can be categorized as non-neoplastic or neoplastic. Neoplastic lesions can be further divided into benign or malignant, with malignancies being either primary or secondary (metastatic). Clinical, radiographic, and pathologic features of the most common entities are discussed. RECENT FINDINGS: Metastatic neoplasms involving the heart and pericardium are far more common than primary pericardial neoplasms. Of primary pericardial malignancies, mesothelioma is the most common; notably, cytology of effusion fluid is relatively insensitive to the diagnosis. The prognosis for most malignancies of the pericardium, primary or secondary, is poor. Increasingly, clinically recognized diseases that involve the pericardium include Erdheim-Chester and IgG4-related disease. This article provides a comprehensive review of the most recent literature to develop a structured framework to the differential diagnosis of pericardial tumors.

Development of sacral/buttock retiform purpura as an ominous presenting sign of COVID-19 and clinical and histopathologic evolution during severe disease course.

Retiform purpura has been described as a relatively frequent cutaneous finding in patients with coronavirus disease 2019 (COVID-19). The etiology is hypothesized to be related to thrombotic vasculopathy based on lesional biopsy specimen findings, but the pathogenesis of the vasculopathy is not completely understood. Here, we present a case of a retiform purpuric patch on the sacrum/buttocks in a hospitalized patient prior to subsequent diagnosis of COVID-19 and an eventual fatal disease course. Two lesional biopsy specimens at different time points in the disease course revealed thrombotic vasculopathy, despite therapeutic anticoagulation. Detailed histopathologic evaluation using immunohistochemical markers suggest the etiology of the vasculopathy involves both persistent complement activation and platelet aggregation, which possibly promote ongoing thrombus formation. This case highlights that sacral/buttock retiform purpuric patches may be a presenting sign of infection with SARS-CoV-2 virus and may represent an ominous sign supporting a future severe disease course. In addition, biopsy specimen findings at separate time points demonstrate that cutaneous vasculopathy may persist despite adequate systemic anticoagulation, possibly due to the combination of persistent complement and platelet activation. Finally, occlusive thrombi in sacral/buttock retiform purpuric patches may contribute to future ulceration and significant cutaneous morbidity in patients who survive COVID-19.