TO THE EDITOR: B-ALL encompasses several distinct subtypes according to the current World Health Organization (WHO) classification of hemato-lymphoid neoplasms. BCR-ABL1–like B-acute lymphoblastic leukemia/lymphoma is a novel provisional entity in B-ALL cases characterized by genetic aberrations in cytokine receptor and/or tyrosine kinase signaling pathways, which gives it a pattern of B-ALL with BCR-ABL1 on gene expression profiling; however, there is no t(9;22) on cytogenetic or molecular genetic analysis [1]. This category has been assigned as a high-risk prognostic subgroup with dismal outcomes [2].

Several studies have described the clinical, biochemical, microbiological, radiological, and histopathological profiles of BCR-ABL1–like ALL. However, currently, there are no autopsy data available for this entity. To the best of our knowledge, this is the first autopsy report of an adult patient with BCR-ABL1–like ALL.

A 29-year-old man was symptomatic with progressive fatigue for six months and fever for one month. The patient had pallor and moderate splenomegaly on clinical examination. His complete blood count (CBC) revealed a hemoglobin level of 78 g/L, platelet count of 9×10⁹/L, and white blood cell (WBC) count of 7.2×10⁹/L with 63% circulating blasts. Bone marrow aspirate showed 94% blasts. Flow cytometry results were consistent with a diagnosis of B-ALL. The genetic analysis of four common recurrent genetic aberrations [namely, t(1;19), t(9;22), t(12;21), and t(4;11)] was negative using reverse-transcriptase polymerase chain reaction. Pre-phase steroid administration was commenced according to the modified Berlin-Frankfurt-Munster (BFM) protocol. He was also administered acyclovir, trimethoprim-sulfamethoxazole, and fluconazole prophylaxis. A week later, he presented with fever, vomiting, one episode of hematemesis, difficulty in swallowing, abdominal pain, and loose stools. Abdominal examination was soft, with the spleen palpable 4 cm below the left costal margin. There was blunting of the cardiophrenic angles on chest radiography. Abdominal ultrasound revealed mild thickening of the gastric antrum, likely to be inflammatory, with kidney sizes of 11.3 and 12 cm. His CBC at this point showed a hemoglobin level of 47 g/L, WBC count of 0.4×10⁹/L, and platelet count of 5×10⁹/L. His creatinine level increased from 0.87 to 1.27 mg/dL. His serum electrolytes were potassium: 4.2 mEq/L, corrected calcium: 7.7 mg/dL, and phosphate: 5.1 mEq/L. He was managed for febrile neutropenia with cefoperazone-sulbactam, azithromycin, intravenous fluids, pantoprazole, and blood and platelet transfusions. Despite this, he progressed to septic shock and sustained cardiac arrest within 60 hours of presentation. The cause of death was attributed to respiratory failure, which was likely due to aspiration pneumonia, septic shock, and febrile neutropenia. There was also a clinical possibility of necrotizing enterocolitis and transfusion-related acute lung injury (TRALI). A partial (abdominothoracic) autopsy was conducted for the clinicopathological correlation.

At autopsy, effusions were present in the abdominal (2,000 mL) and bilateral pleural (1,000 mL together) cavities. The bone marrow revealed 95% blasts along with hemophagocytosis and marrow edema (Fig. 1A–E). Enlarged para-aortic LNs with leukemic infiltrates and hemophagocytosis were also noted. The spleen was enlarged, weighing 370 g (normal, 150–200 g) with preserved white pulp showing CD20⁺/TdT⁺ blasts (Fig. 1F–H). Extramedullary hematopoiesis was present in the expanded red pulp in the form of erythroid precursors and megakaryocytes (Fig. 1I). The liver weighed 1700 g (normal, 1,500–1,800 g) and was grossly unremarkable (Fig. 1F). Portal tracts on microscopy were mildly expanded (Fig. 1J) with scattered CD20⁺/TdT⁺ blasts. Similar leukemic infiltrates were also seen in the exocrine pancreas (Fig. 1K), visceral pericardium, and endocardium (Fig. 1L, M). Grossly, both kidneys were unremarkable, but heavy leukemic infiltrates were observed around the glomeruli and interstitium (Fig. 2).

In an attempt to further characterize B-ALL at the genetic level, DNA and RNA were extracted from formalin-fixed, paraffin-embedded renal tissue with areas of maximum leukemic infiltrates. To analyze the BCR-ABL1–like B-ALL genetic signature, an initial assessment was performed for cytokine receptor-like factor 2 (CRLF2) gene overexpression using quantitative real-time polymerase chain reaction (qRT-PCR) with the extracted RNA and cDNA synthesized material (as described previously) [3]. Multiplex ligation-dependent probe amplification analysis of genomic DNA to detect copy number alterations (CNAs) was also performed for the BCR-ABL1–like B-ALL genetic signature. The case was positive for CRLF2 overexpression (∼280 times) with poor-risk CNAs, such as deletions in IKZF1, JAK2, RB1, and PAX5 (Fig. 2). Further characterization of CRLF2 rearrangements and JAK2 mutations was technically non-contributory. However, in view of CRLF2 overexpression and the detected CNAs, the case was finally labelled as BCR-ABL1–like B-ALL (WHO 2016 classification).

Both the lungs demonstrated diffuse consolidation, and major vessels had thrombi around the area of hemorrhage (Fig. 3A, B). During the microscopic examination, the thrombi revealed a fungal profile (Fig. 3C), which was identified as Rhizopus species on molecular subtyping. Moreover, some other fungal hyphae conforming to the morphology of Trichosporon species (Fig. 3D) were also identified. Other pulmonary pathologies were an evidence of bronchopneumonia with gram-positive organisms, terminal aspiration in bronchioles, and focal leukemic infiltrates. The stomach wall was diffusely thickened (5 mm) and ulcerated (Fig. 3E, F). On microscopy, the submucosa was extensively edematous and had fibrin thrombi in the vessels, but there was no evidence of any infection or leukemic infiltrates. These findings are consistent with acute phlegmonous gastritis (Fig. 3G, H). The jejunum showed multiple transversely oriented linear ulcers (Fig. 3I). Histopathological examination revealed superficial ulcers limited to the submucosa (Fig. 3J, K). The vessels surrounding these ulcers showed fibrin thrombi, and many of them were clogged with fungal hyphae (Fig. 3L) of the Aspergillus species (morphologically). The remaining dissected organs were unremarkable.

Acute leukemias have heterogeneous clinical presentations, laboratory features, and varied responses to established therapies. The main diagnostic modalities are peripheral blood and bone marrow examination, together with the necessary baseline biochemical and radiological investigations. Assessment of response to therapy is usually assessed using follow-up blood counts, bone marrow remission status, and minimal residual disease estimation using flow cytometry and/or molecular markers. Even after assessing all these parameters, patients may not undergo remission or show a relapse. As it is a systemic disease, accurate assessment of residual disease (which may be extramedullary) and other confounding factors such as infections may be missed or overlooked. These cases may ultimately demonstrate dismal outcomes.

The practice of autopsy pathology has been an invaluable tool to understand the etiopathogenesis. Much of the current knowledge regarding the various aspects of different diseases is a result of vivid and varied descriptions by pioneers in the field of autopsy pathology. The original studies describing autopsy cases of hematological malignancies have been published in the English literature in the 1980s [4]. Since then, there have been significant advances in diagnostic criteria and management protocols for this disease. There is only one recent study describing the autopsy pathologies of cases of acute myeloid leukemia and non-Hodgkin lymphoma, which has shed light on the new findings [5]. Hence, there is a need to revisit autopsy pathology in cases of hematological malignancies, especially in the current era of hematopoietic stem cell transplantation and other advanced therapeutic modalities.

The current case report describes the autopsy findings for the first time in the literature. Although the case was managed according to the hospital guidelines, the patient still succumbed to his illness, and the autopsy revealed certain pathologies that were not thought of during his life, which could have been managed. In this case, the active disease burden was also seen outside the lymphoreticular system in the form of heavy leukemic infiltrates in the kidneys, portal tracts, exocrine pancreas, and heart. Previous autopsy studies during the 1960s and 70s have also reported malignant infiltration in these extramedullary sites; however, the underlying mechanism remains unknown [5]. This can be attributed to the limited understanding of the molecular aspects of the heterogeneous nature of acute leukemias. In light of recent developments in the understanding of this disease, the mechanisms of disease progression are being explored. The migration capabilities of leukemic cells into the extramedullary sites are related to the expression and orchestration of adhesion molecules, such as CD44 and P/E-selectins, and chemokines and their receptors [6]. According to the current understanding of BCR-ABL1–like B-ALL, CRLF2 overexpression activates the JAK/STAT and PI3K signaling pathways [7]. The exact mechanisms linking these pathways to the augmented expression of adhesion- and migration-related molecules remain to be elucidated.

The other significant aspect for the case was a clinicopathological miscorrelation seen with regards to pulmonary and gastrointestinal pathology. TRALI and necrotizing enterocolitis were thought to be fungal infections and acute phlegmonous gastritis. These pathologies are rapidly fatal and require prompt measures for management [8, 9]. Autopsy revealed different morphological subtypes of fungal species, which may require a different therapeutic approach [8]. Hence, this report revealed certain aspects that might be encountered in BCR-ABL1–like B-ALL patients, which could be responsible for its high-risk category. This need to be further elucidated by large autopsy studies.

Another aspect of this case is the potential of the autopsy material, which was utilized in the diagnosis of BCR-ABL1–like B-ALL. Appropriate attempts were strategically made from renal leukemic infiltrates for molecular genetic analysis to further characterize this case. Targeted therapies are now available for BCR-ABL1–like B-ALL subtype that lead to better outcomes [10]. Furthermore, the molecular characterization of fungal infection (Rhizopus species) was also investigated using autopsy material.

In summary, we describe the first report of a BCR-ABL1–like B-ALL case emphasizing the use of autopsy practice to further understand the pathobiology of hematological malignancies. The clinicopathological correlation was analyzed to gain insights into this entity. Certain learning points were the pattern of leukemic infiltrates, the plethora of fungal infections, and the use of autopsy material for ancillary techniques.