Modern Pathology最新文献

Anaplastic lymphoma kinase (ALK)-positive histiocytosis is a rare histiocytic neoplasm defined by oncogenic ALK fusions. The disease frequently involves the nervous system and is responsive to ALK inhibition. A distinct subset of histiocytoses express ALK in the absence of detectable ALK fusions. We aimed to determine the frequency and molecular characteristics of these ALK protein-positive, fusion-negative neoplasms. RNA was extracted from histiocytosis-affected tissue samples of 398 patients with diverse histiocytoses, converted to cDNA, and subjected to targeted sequencing using a custom gene panel. ALK fusions and gene expression levels were assessed; the presence of ALK isoforms was investigated using targeted digital PCR. In a subset of cases, ALK protein expression was evaluated using immunohistochemistry (clone 1A4). Of 398 cases, 303 (76%) passed quality control and were included in the analysis. Among these, 64 (21.5%) had substantial ALK gene expression, while not harboring ALK fusions. Immunohistochemistry revealed consistent nuclear and cytoplasmic ALK expression in these cases, whereas ALK expression in fusion-positive cases was restricted to the cytoplasm. Analysis of ALK intron 19 expression by targeted PCR revealed the presence of a novel ALK isoform (ALK^ATI) that was linked to nuclear ALK expression. No specific clinical or molecular features distinguished histiocytic neoplasms with ALK^ATI from those without. In conclusion, many histiocytic neoplasms express ALK but are not ALK-positive histiocytosis. Most cases can be identified by nuclear ALK expression, which is linked to alternative transcription initiation - a known mechanism of ALK activation independent of genetic aberrations. Future studies should elucidate whether these neoplasms respond to ALK inhibition.

The lineage of the Kaposi sarcoma (KS) tumor cell remains elusive, limiting opportunities for targeted therapy. We performed concurrent spatial imaging of five bona fide lymphatic endothelial cell (EC) markers together with the KSHV viral protein LANA in thirty well-characterized HIV-positive KS biopsies (n = 1,740,744 cells). Nodular KS lesions showed significantly more circular nuclei than plaque KS, indicating distinct cellular morphologies. Both forms contained dense areas of LANA-positive cells-termed "LANA nests." Among the EC markers, VEGFR-3 was most abundantly expressed, although many VEGFR-3-positive cells were LANA negative. Podoplanin (PDPN) and LYVE-1 consistently colocalized with each other, whereas CD31 and VE-Cadherin were variably expressed within and across lesions. Together, these observations reveal that KS lesions are composed of multiple microenvironments: LANA-dense nests, LANA-sparse fascicles, and mature lymphatic or blood vessels, some of which also harbored LANA-positive lining cells. At present, targeted therapies do not account for this variability; generally, responses are not based on pathology. Spatial changes in the tumor microenvironment that may provide insights into drug action and resistance mechanisms are missed.

In 2021, the International Myeloma Working Group lowered the threshold to establish the diagnosis of primary plasma cell leukemia (pPCL) from ≥ 20% to ≥ 5% circulating plasma cells (CPCs) as assessed by morphologic evaluation (ME). However, the threshold for defining secondary PCL (sPCL) remains unclear. We retrospectively studied the clinicopathological features of 52 PCL patients, 30 pPCL and 22 sPCL, with ≥ 5% CPCs determined by either ME or flow cytometry immunophenotyping (FCI). FCI often revealed a higher percentage of CPCs than ME, likely due to difficulties in identifying morphologically abnormal plasma cells with certainty, and this discordance was statistically significant in sPCL patients. pPCL and sPCL both exhibited leukocytosis, thrombocytopenia, infrequent CD56 expression, high bone marrow tumor burden and complex karyotypes. MYC rearrangement was observed only in sPCL cases. Paired cytogenetic data before and after leukemic transformation were available in a small subset of sPCL patients (8/22). Compared with the prior myeloma, sPCL more frequently harbored a complex karyotype, hypodiploidy and additional cytogenetic abnormalities, most commonly gain of chromosome 1q. Using 5% CPCs as the diagnostic threshold, patients with sPCL had significantly poorer outcomes than patients with pPCL (p < 0.0001). Furthermore, the outcomes of sPCL patients with 5-19% CPCs were similarly poor as those patients with ≥ 20% CPCs (p = 0.4781), highlighting the need to recognize patients with ≥ 5% CPCs promptly. FCI appears to be a more sensitive method for this purpose in most cases. Using FCI, further studies are needed to determine whether a diagnostic threshold of 5% or lower may be used to establish the diagnosis of sPCL.

Non-Hodgkin lymphoma (NHL) is a diverse and heterogeneous group of hematologic malignancies. These lymphomas arise from the clonal proliferation of either B-/T- or Natural Killer lymphocytes, and their correct classification relies partly on identifying characteristic structural variants (SV) and copy number alterations (CNA). Current standard of care technologies for detecting these genomic features, chromosome banding analysis (CBA) and fluorescent in-situ hybridization (FISH), are labor-intensive and have specific limitations. CBA has low resolution and relies on viable cell culture, while the targeted approach of FISH does not provide the whole genome view required for comprehensive disease characterization. This highlights the need for higher-resolution non-targeted genomic methods. Previous studies have evaluated optical genome mapping (OGM) as a whole-genome alternative for cytogenomic characterization in NHL diagnostics but were restricted in number and to cases with peripheral blood and/or bone marrow invasion. Here, we selected a comprehensive cohort of 110 NHL cases (79 B-NHL and 31 T/NK-NHL), derived from different types of tissue biopsies, all with established histopathologic diagnoses. 78 samples were genomically well-characterized at diagnosis by CBA and FISH. The remaining 32 cases were included due to prior CBA failure, although FISH data was available for 20 cases. OGM provided informative results in 94% of the cohort, with a high concordance rate of 97.6% compared to CBA/FISH in detecting clinically relevant aberrations. The two variants that were missed, were both present at the detection threshold of OGM. In contrast, OGM successfully resolved 26 samples with prior CBA failure and detected three additional disease-defining events, resulting in diagnostic reclassification of one patient. Lastly, OGM identified novel recurrent aberrations that warrant further investigation into their pathogenetic implications. In conclusion, OGM robustly detects clinically relevant SV and CNA and presents a promising alternative to CBA and FISH in routine diagnostic evaluation of NHL.