Journal of Pathology and Translational Medicine

Articles in E-pub version are posted online ahead of regular printed publication.

Original Articles

Increased Toll-like receptor 9 expression associated with cellular proliferation and poor prognosis in pleural mesothelioma: Ali Omar Abdelaziz, Dina Moustafa Thabit, Rehab Mohamed Kamal, Hend Moness, Rasha Fouad Ahmed, Mariana Fathy Gayyed, Fatma El Zahraa Ammar Mohamed; Received April 30, 2025 Accepted April 1, 2026 Published online May 26, 2026; DOI: https://doi.org/10.4132/jptm.2026.04.01 [Epub ahead of print]

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Abstract PDF Supplementary Material: Background
Pleural mesothelioma is an aggressive malignancy with a poor prognosis. The epithelioid subtype is the most common and can be challenging to distinguish from metastatic lung adenocarcinoma (MLAC). The role of Toll-like receptor 9 (TLR9) in the progression of pleural mesothelioma remains unclear. Methods: A total of 30 pleural biopsy specimens were collected, comprising 10 cases of pleural epithelioid mesothelioma and 20 cases of MLAC. The mRNA expression levels of TLR9 and proliferating cell nuclear antigen (PCNA) were quantified. In addition, sixty archived formalin-fixed, paraffin-embedded tissue blocks (40 epithelioid mesothelioma and 20 MLAC) were analyzed via immunohistochemistry using an anti-TLR9 antibody in relation to various clinicopathological parameters. Results: TLR9 expression was significantly higher in epithelioid mesothelioma cases than in MLAC cases (p < .001), with mean values of 1.54 ± 0.09 and 1.02 ± 0.08, respectively. A significant positive correlation was observed between TLR9 and PCNA expression levels specifically in the epithelioid mesothelioma cohort (p < .001, r = 0.8). Furthermore, immunohistochemical analysis confirmed that high TLR9 immunoexpression was significantly more prevalent in epithelioid mesothelioma (36/40 cases; 90%) than in MLAC (3/20 cases; 15%) (p < .001). Notably, elevated TLR9 expression was associated with a significantly shorter overall survival (p = .001). Conclusions: In conclusion, TLR9 expression is significantly elevated in epithelioid mesothelioma compared to MLAC at both the molecular and cellular levels, and its expression correlates with increased tumor proliferation and poorer prognosis. Our data suggest that TLR9 could represent a promising diagnostic and prognostic biomarker, warranting further investigation into its potential therapeutic applicability.

A single-institution demographic study of pathologically proven renal disease in kidney transplant recipients over the last 33 years: Hyejin Noh, Jiyeon Kim, Yeong Jin Choi; Received September 16, 2025 Accepted March 28, 2026 Published online May 26, 2026; DOI: https://doi.org/10.4132/jptm.2026.03.28 [Epub ahead of print]

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Abstract PDF Supplementary Material: Background
While the number of kidney transplants for end-stage renal disease (ESRD) is increasing, studies examining the long-term demographic analyses based on pathological diagnosis of transplant kidney remain limited. Methods: We conducted a retrospective analysis of 4,188 transplant recipients who underwent either biopsy or nephrectomy from 1991 to 2023 at Seoul St. Mary’s Hospital. Results: Among 7,229 pathologically confirmed cases, rejection was the most prevalent (37.8%), followed by tubulointerstitial (25.4%), glomerular, drug toxicity, and vascular diseases. In 7,053 transplant biopsies, rejection was predominant across all age groups, with T-cell mediated (TCM) category being the most common (60.1%), followed by antibody-mediated and mixed. Drug toxicity increased with age (p = .047), while glomerular and tubulointerstitial diseases were highest in recipients under 20 (p < .001). Among glomerular diseases, IgA-related glomerulonephritis (45.2%) was the most common. In 176 transplant nephrectomies, the most common diagnosis was rejection (33.5%), followed by renal infarction (19.9%), tubulointerstitial, vascular, glomerular disease, and drug toxicity. “Others” included infarction, ESRD, and lymphangiectasia, which increased with age (p = .011). In nephrectomy cases, rejection decreased over time, with chronic TCM rejection (40.7%) being the most frequent. Conclusions: This study provides valuable insights into transplant kidney disease in South Korea. The number of transplant biopsies has increased over the past 33 years, while the number of nephrectomies has remained unchanged. Rejection was the most common finding in all age groups in biopsies, but decreased with age in nephrectomies, with TCM being the most common and observed more often in younger recipients.

Case Study

Phenotypic plasticity in plasma cell myeloma: a CD138-negative case with a rare BRAF G469R mutation: Sun-Ju Oh, So-Hak Chung; Received November 21, 2025 Accepted February 2, 2026 Published online April 22, 2026; DOI: https://doi.org/10.4132/jptm.2026.02.02 [Epub ahead of print]

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Abstract PDF: CD138-negative plasma cell myeloma harboring a BRAF G469R mutation is described in a 76-year-old male presenting with multiple osteolytic lesions. Histologically, the lesion exhibited epithelioid to plasmacytoid morphology with prominent mitotic activity and vascular-like spaces. Immunophenotyping demonstrated strong vimentin and CD31 expression but absence of CD138 and other endothelial markers. Light-chain in situ hybridization confirmed a clonal κ-restricted plasma cell population. Bone marrow examination revealed near-complete replacement by atypical plasma cells, retaining CD138 negativity and demonstrating focal CD20 positivity, indicative of intratumoral heterogeneity. Next-generation sequencing identified a rare BRAF G469R variant. The patient exhibited poor response to bortezomib, lenalidomide, and dexamethasone therapy, necessitating a switch to carfilzomib-based treatment. This case underscores the diagnostic challenges of CD138-negative myeloma and highlights the importance of integrating morphology, immunophenotyping, and molecular profiling to inform accurate diagnosis and guide therapeutic strategies.

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