To appreciate why this case matters, it helps to understand the biology. Anaplastic lymphoma kinase (ALK) rearrangements occur in roughly three to five percent of non-small cell lung cancers (NSCLC), most commonly in younger, never-smoking patients with adenocarcinoma histology. The rearrangement fuses the ALK gene with a partner gene, producing a constitutively active signaling kinase that drives uncontrolled cell growth. Because the malignant cell becomes addicted to this single aberrant signal, ALK inhibitors—starting with crizotinib and progressing through second- and third-generation agents such as alectinib, brigatinib, and lorlatinib—can produce dramatic and durable responses. Sequential use of these next-generation inhibitors has pushed median survival for ALK-positive metastatic disease into territory once unimaginable for stage IV lung cancer.

Yet resistance is inevitable. Tumors evolve under selective pressure, and the mechanisms they deploy fall into two broad categories. The first is on-target resistance: secondary mutations within the ALK kinase domain itself, such as the notorious G1202R substitution, which alters the drug-binding pocket and prevents inhibitors from latching on. The second is bypass signaling: the tumor rewires its circuitry, activating an entirely parallel pathway—often through amplification of MET or KIT, activation of RAS/MAPK, or transformation to small-cell histology—so that blocking ALK no longer matters. The third and rarest category is the acquisition of a bona fide driver mutation in a different gene, one that is itself clinically actionable. The present case falls squarely into this last, uncommon group.

The patient’s treatment course, as documented by Junyue Deng, Juan Li, and colleagues at the Cancer Center of Daping Hospital, Army Medical University, in collaboration with the Geneseeq Research Institute, reads like a tour of modern ALK therapeutics. She received crizotinib, the first-generation inhibitor, followed by alectinib, lorlatinib, and brigatinib in sequence, achieving exceptionally durable disease control for nearly nine years. Each drug in that lineup was deployed to overcome or forestall resistance to its predecessor, a strategy that has become standard practice in ALK-positive disease and that the case demonstrates can buy years of high-quality life.

The turning point came when the disease progressed despite multiple ALK inhibitors. Rather than simply switching to another ALK drug and hoping for the best, the clinical team performed next-generation sequencing (NGS) on cell sediment from a pericardial effusion—the fluid that had accumulated in the sac surrounding the heart. This is a technically meaningful choice. Pericardial effusion in advanced cancer often contains malignant cells, and its cell sediment can yield DNA of sufficient quality for targeted sequencing. When tissue biopsy is difficult, risky, or infeasible—particularly when the relevant disease site is deep in the chest or the patient is frail—effusion-based molecular profiling offers a minimally invasive window into the tumor’s current genotype.

The sequencing result was striking: an EGFR L858R mutation with a variant allele frequency (VAF) of 12.05 percent. L858R is one of the two classic sensitizing EGFR mutations in lung adenocarcinoma, substituting a leucine at position 858 of the EGFR kinase domain with an arginine. The substitution destabilizes the inactive conformation of the kinase, locking the receptor into its active state and rendering it exquisitely sensitive to EGFR tyrosine kinase inhibitors. Crucially, the team also performed retrospective NGS on the patient’s archival baseline lymph node specimen—the tissue obtained at diagnosis before any therapy—using the same DNA-based targeted panel. That original sample contained neither the EGFR L858R mutation nor, notably, a detectable ALK fusion. The comparison strongly suggests that the EGFR mutation was acquired during treatment, a genuine instance of clonal evolution under drug pressure rather than a co-existing alteration missed at baseline.

The clinical response to this molecular detective work was immediate and gratifying. Treatment was switched to osimertinib, the third-generation EGFR inhibitor designed to selectively target sensitizing EGFR mutations while sparing wild-type EGFR, thereby limiting the skin and gastrointestinal toxicity that plagued earlier EGFR drugs. Under RECIST 1.1 criteria—the international standard for measuring tumor burden on imaging—the patient achieved a partial response, meaning a substantial shrinkage of measurable lesions. This was accompanied by a marked decline in serum carcinoembryonic antigen (CEA), a tumor marker whose falling levels served as an independent biochemical confirmation that the EGFR-driven clone was being brought under control. Disease control has been maintained through month 107 of her overall treatment course.

The implications of this single case ripple outward in several directions. First, it reinforces a principle that oncologists repeat like a mantra but that is still unevenly applied in practice: re-biopsy at progression matters. When a tumor stops responding to a targeted therapy, the resistance mechanism cannot be reliably guessed. Secondary ALK mutations, bypass activation, phenotypic transformation, and—as here—an entirely new druggable driver can all be at play, and each demands a different therapeutic answer. Treating progression blindly risks burning months on a drug the tumor has already outmaneuvered. Repeat molecular profiling, whether from tissue, blood plasma, or effusion specimens, converts a guessing game into a rational prescription.

Second, the case highlights the value of cytology-based and effusion-based sequencing as a complement to tissue biopsy. Pericardial effusions are clinically significant events in advanced NSCLC, and their malignant cell sediment is often discarded after cytological diagnosis. The demonstration that this material can yield an actionable result—here, a mutation at a VAF above 12 percent, well within the detection range of standard targeted panels—argues for routine molecular profiling of such specimens whenever conventional sampling is impractical. It also underscores why paired analysis of archival baseline tissue and progression-time samples is so informative: without the retrospective sequencing of the original lymph node, the acquired nature of the EGFR mutation would have remained uncertain, and the possibility of a baseline co-mutation misclassified as primary ALK-driven disease could not have been excluded.

Finally, the report is a vivid illustration of how far sequential targeted therapy has come. A patient diagnosed with stage IV ALK-positive lung cancer once faced a prognosis measured in months; this woman has lived through four generations of ALK inhibitors and then pivoted to a fifth targeted drug against a different kinase, remaining in ongoing disease control nearly nine years on. Resistance, in this framing, is not a wall but a series of doors—each opened by understanding the tumor’s latest move. The case, published open access with the support of the Science-Health Joint Medical Scientific Research Project of Chongqing, adds to the growing evidence that vigilant, repeated genomic surveillance can keep patients with driver-mutant lung cancer one step ahead of their disease. For clinicians, the message is clear: when ALK-targeted therapy fails after years of success, look again at the tumor’s genome, because the answer may be another approved drug waiting in the wings.

Subject of Research: Acquired EGFR L858R mutation as a resistance mechanism to sequential ALK inhibitor therapy in ALK-rearranged non-small cell lung cancer

Article Title: Detection of an EGFR L858R mutation following prolonged sequential ALK-TKI therapy in ALK-rearranged NSCLC: a case report

Article References: Detection of an EGFR L858R mutation following prolonged sequential ALK-TKI therapy in ALK-rearranged NSCLC: a case report. (n.d.). https://doi.org/10.1007/s00432-026-06604-8

Image Credits: AI Generated

DOI: 10.1007/s00432-026-06604-8

Keywords: ALK-rearranged NSCLC, EGFR L858R, acquired resistance, ALK inhibitors, osimertinib, next-generation sequencing, pericardial effusion, liquid biopsy, targeted therapy, lung cancer, case report, tumor evolution

What happened next transformed this routine infection into a diagnostic puzzle that physicians rarely encounter. By hospital day 11, imaging showed that the right upper lobe infiltrate had resolved, but new bilateral pleural effusions had appeared in its place. Thoracentesis was performed on both sides of the chest, and both effusions were grossly bloody and exudative. Yet beneath that identical bloody appearance lay a startling discordance: the right-sided fluid was dominated by neutrophils, at 85 percent, while the left-sided fluid was dominated by lymphocytes, at 90 percent. Cytology was negative for malignancy in both samples, and cultures grew no organisms. A single systemic process, such as heart failure or carcinomatosis, could not plausibly produce two fluids with such different cellular signatures. Instead, the findings pointed toward two entirely independent diseases developing simultaneously in the same chest.

The right effusion was straightforward to explain. Parapneumonic effusions are a well-recognised complication of bacterial pneumonia, particularly pneumococcal infection, in which parenchymal inflammation extends to the pleural space and generates a protein-rich, neutrophil-dominant exudate driven by acute inflammation. The antibiotic therapy was working against the pneumonia itself, but the severe initial inflammatory burden likely led to a delayed manifestation of pleurisy, with effusions emerging even as the lung infiltrate retreated. That mechanism accounted for the right hemithorax. The left effusion, with its lymphocyte predominance and later behaviour, was a far more elusive entity that would take months to reveal its full character.

The bloody appearance of both effusions added another layer of complexity. The patient’s antithrombotic regimen included edoxaban, a direct oral anticoagulant, along with aspirin, prescribed after coronary artery bypass grafting approximately 12 months earlier for acute coronary syndrome. Direct oral anticoagulants have been reported to induce spontaneous pleural bleeding, and the clinicians hypothesised that the combination of anticoagulant and antiplatelet therapy exacerbated microvascular oozing within inflamed pleura. Notably, however, the red blood cell counts in the effusions were relatively modest, yielding calculated pleural fluid haematocrits of only 0.18 percent on the right and 0.44 percent on the left, far below the diagnostic threshold for haemothorax. In other words, the bleeding tendency likely painted the exudates red without fundamentally changing their underlying inflammatory nature.

Management reflected the uncertainty. Given the bloody effusions, the team discontinued only the edoxaban and administered haemostatic agents, while continuing aspirin after consultation with the cardiovascular surgery team. Follow-up chest CT on May 21 showed partial resolution of the effusions, and with fever and hypoxaemia resolved, the patient was discharged on May 23. He remained stable as an outpatient for three months. Then, in late August, the left effusion worsened, and a concurrent chest CT revealed a small pericardial effusion that was too small for pericardiocentesis. A repeat left thoracentesis again yielded bloody, lymphocyte-dominant fluid, and C-reactive protein, which had normalised after discharge, had crept back above the institutional upper limit of normal. Echocardiography demonstrated preserved left ventricular function, arguing against heart failure as the cause.

This late recurrence allowed the clinicians to apply formal diagnostic criteria. The 2015 European Society of Cardiology guidelines for pericardial diseases require at least two of five criteria for a diagnosis of post-cardiac injury syndrome, the category that encompasses Dressler syndrome. The patient fulfilled two: pericardial effusion on CT and pleural effusion with elevated inflammatory markers. Fever, pericarditic or pleuritic chest pain, and audible rubs were all absent, making the presentation distinctly indolent. Late-onset Dressler syndrome was suspected, and the team initiated diagnostic therapy with ibuprofen at 600 mg per day, the maximum dose covered by Japanese medical insurance. Follow-up imaging confirmed significant improvement of both the left pleural and pericardial effusions, and no recurrence occurred during 10 months of follow-up after the anti-inflammatory treatment began.

Dressler syndrome is an immune-mediated pleuropericarditis that classically appears within weeks to a few months of cardiac injury, most often after cardiac surgery such as coronary artery bypass grafting. The prevailing pathophysiological model holds that cardiac injury releases sequestered cardiac antigens, triggering the formation of anti-heart autoantibodies. The time required for this immunological sensitisation inherently creates a latent period between injury and clinical onset. The reported profile of post-cardiac injury syndrome effusions fits this patient’s left-sided fluid almost exactly: such effusions are unilateral in about two thirds of cases and left-sided in the large majority, with no Dressler syndrome patients in one published series showing right-sided unilateral effusions; nearly all are exudates, and roughly three quarters are lymphocyte-predominant.

The timing, however, was extraordinary. Onset occurred approximately 12 months after bypass surgery, exceeding not only the usual latent window but also the nine-month interval described in one of the longest previously reported cases. The authors propose a two-hit hypothesis: the patient developed long-standing latent immune sensitisation following his cardiac surgery, and the intense systemic inflammatory response generated by severe pneumococcal pneumonia acted as a necessary catalyst, reactivating the dormant autoreactive process and culminating in the delayed manifestation of Dressler syndrome. In this framing, the pneumonia did not merely coexist with the immune syndrome; it may have ignited it. The two mechanisms are not mutually exclusive, and an immune-mediated predisposition related to prior cardiac injury may have been unmasked by systemic inflammation from the contralateral infection.

The authors are careful to acknowledge residual diagnostic uncertainty, since a response to non-steroidal anti-inflammatory drugs is common in pleuropericarditis of virtually any cause. A reactive post-infectious serositis following the pneumonia remains a plausible alternative, as autoimmune pleuropericarditis has been reported after community-acquired pneumonia, including Chlamydia pneumoniae-associated cases. Furthermore, no pericardial effusion was present at the time of the initial thoracenteses, and the left effusion was attributed to a post-cardiac injury process only retrospectively, once the August recurrence fulfilled the formal criteria. The lymphocyte-predominant profile and prompt ibuprofen response support an immune-mediated process, but they do not definitively tie it to the prior surgery rather than the preceding infection. Late-onset Dressler syndrome is therefore presented as the most likely clinical diagnosis rather than a certain one.

The broader lesson reaches well beyond this single patient. Clinicians frequently assume that bilateral pleural effusions stem from a single systemic aetiology such as heart failure, renal failure or malignancy, and this assumption can obscure independent localised pathologies that demand separate therapeutic strategies. In this case, the two sides of the chest required targeted antibiotic therapy on the right and anti-inflammatory treatment on the left, and neither intervention alone would have addressed both conditions. The definitive clue was not the grossly bloody appearance, which was identical on both sides and heavily influenced by antithrombotic medications, but the rare and striking discordance of pleural fluid cellular profiles between hemithoraces. For patients with bilateral effusions whose clinical or radiological presentation is atypical, the case argues strongly for bilateral thoracentesis with detailed cellular analysis, a practice this team believes should be adopted far more widely. To their knowledge, a PubMed search identified no previous report of parapneumonic effusion and Dressler syndrome presenting concurrently, and the combination is classically described under the label of Contarini syndrome, in which each side of the chest harbours a different cause.

Subject of Research: A rare case of bilateral bloody pleural effusions arising from two independent causes, concurrent parapneumonic effusion and suspected late-onset Dressler syndrome, distinguished by discordant pleural fluid cellular profiles.

Article Title: Bilateral Bloody Pleural Effusions With Discordant Cellular Patterns: A Case of Concurrent Parapneumonic Effusion and Dressler Syndrome

Article References: Narumi, Y., Hoshino, S., Yamakawa, M., & Amano, Y. (2026). Bilateral Bloody Pleural Effusions With Discordant Cellular Patterns: A Case of Concurrent Parapneumonic Effusion and Dressler Syndrome. Respirology Case Reports, 14(9), Article e70764. https://doi.org/10.1002/rcr2.70764

Image Credits: AI Generated

DOI: 10.1002/rcr2.70764

Keywords: pleural effusion, Dressler syndrome, post-cardiac injury syndrome, parapneumonic effusion, Streptococcus pneumoniae, thoracentesis, coronary artery bypass grafting, edoxaban, lymphocyte-dominant exudate, Contarini syndrome, pericardial effusion, ibuprofen