This high-power light micrograph of a lymph node biopsy, stained with Hematoxylin and Eosin, demonstrates classical Hodgkin lymphoma histology. The tissue is densely cellular with a polymorphic inflammatory background comprising small lymphocytes, eosinophils, plasma cells, and histiocytes. Scattered among the background are large binucleated Reed-Sternberg (RS) cells exhibiting prominent, mirror-image eosinophilic nucleoli and ample cytoplasm, giving an owl's eye appearance. Mononuclear RS variants with similar nuclear features are present, reflecting heterogeneity within the malignant cell population. The RS cells may appear with delicate nuclear membranes and occasional lobulation. The surrounding milieu often includes reactive T-lymphocytes and occasional eosinophils attracted by cytokines produced by RS cells. The overall architecture lacks well-formed nodules, and the background shows a mixed inflammatory infiltrate, characteristic of classical Hodgkin lymphoma subtypes such as mixed cellularity. Important differential considerations include infectious or benign reactive processes, but the presence of RS cells with classic morphology supports a diagnosis of classical HL. Clinically, these findings correlate with nodal enlargement and B symptoms in many patients, and histology guides staging and therapy decisions, including chemotherapeutic regimens such as ABVD and potential radiotherapy in select cases. Correlation with immunohistochemistry and clinical data improves diagnostic confidence and treatment planning for patient care.

This histopathology image depicts a hematoxylin and eosin (H&E) stained lymph node biopsy section examined under bright-field light microscopy. The predominant nodular sclerosis pattern features fibrous bands dividing the paracortex into discrete nodules. Within the nodules, numerous Reed-Sternberg (RS) cells and Hodgkin cells are evident; RS cells frequently display binucleation with prominent eosinophilic nucleoli and an 'owl's eye' appearance. A lacunar variant of RS cells may be present, characterized by abundant pale cytoplasm and retraction artifacts in formalin-fixed tissue. Background inflammatory cells are relatively sparse but include small lymphocytes and occasional eosinophils; overall lymphoid architecture is disrupted by collagenous septa. The appearance is characteristic of classic Hodgkin lymphoma, nodular sclerosis subtype, which often presents with mediastinal or nodal involvement. Diagnostic significance lies in identifying RS/Hodgkin cells amid a fibrotic nodular framework, supporting a diagnosis of cHL and guiding therapy decisions. Clinically, this image is relevant for educational purposes, hematopathology training, differential diagnosis discussions with reactive lymphadenopathy, NLPHL distinctions, and confirmation of HL subtypes. Potential diagnoses to consider include nodular sclerosis cHL versus NLPHL, other B-cell lymphomas; immunophenotypic studies (CD30+, CD15+, PAX5 weak) and staging (PET-CT) commonly accompany histology for treatment planning.

Histopathology image: Lymph node biopsy stained with Hematoxylin and Eosin (H&E) examined under light microscopy, high magnification. The sample displays lymphoreticular tissue composed of a dense inflammatory background with numerous small lymphocytes and occasional histiocytes. Scattered large atypical cells with prominent nucleoli are identifiable, consistent with Reed–Sternberg (RS) cells and their variants. In this Grade II presentation of nodular sclerosis classical Hodgkin lymphoma (cHL), numerous, bizarre, anaplastic RS cells are seen within a milieu that lacks substantial lymphocyte depletion. The architectural pattern may include nodularity interspersed by fibrous bands, a characteristic of nodular sclerosis, although the image emphasizes individual RS cells and a reactive infiltrate. The RS cells resemble owl-eye nucleoli within a large cytoplasm; immunophenotype typically CD30+, CD15+, CD20−/variable, PAX5 weak, EBV status variable. The observed features correspond to a higher-grade cHL subset, yet grading is primarily a research construct and not essential for routine clinical management. Clinically, this histology correlates with aggressive behavior in some nodal HL cases but usually responds to standard chemotherapy regimens. The image is useful for education about HL morphology, RS cell pleomorphism, differential diagnosis (anaplastic large cell lymphoma, NLPHL, reactive lymphoid hyperplasia) and research correlations in HL grading strategies.

Multi-modal diagnostic imaging of the lumbar spine showcasing a case of lytic spondylolisthesis scheduled for MIS-TLIF. Panel A (Anterior-Posterior X-ray) and B (Lateral X-ray) demonstrate lumbar spinal alignment with a visible grade I or II anterolisthesis at the L4-L5 level. Panel C consists of sagittal CT reconstructions highlighting a fractured pars interarticularis (spondylolysis) at the affected level, contributing to the instability. Panel D (Sagittal MRI) and E (Axial MRI) provide soft tissue detail, showing the relationship between the slipped vertebral body, the intervertebral disc, and the neural elements within the spinal canal. The MRI axial cut (E) specifically illustrates the status of the spinal canal and foraminal space at the level of the slip. Collectively, these images represent the preoperative workup for a minimally invasive transforaminal lumbar interbody fusion (MIS-TLIF) to address spondylolytic spondylolisthesis.

This composite figure displays multi-modal preoperative diagnostic imaging of the lumbar spine, focusing on the L4-L5 segment. Panel A consists of plain radiographs in anterior-posterior and lateral views (neutral, flexion, and extension), demonstrating Grade I degenerative anterolisthesis of the L4 vertebral body relative to L5. Key features include vertebral malalignment, intervertebral disc space narrowing, and osteophyte formation. Panel B presents sagittal and axial T2-weighted MRI scans, highlighting soft tissue pathologies such as segmental spinal canal stenosis and compression of the spinal cord and nerve roots associated with the slip. Panel C shows axial CT scans in bone and soft tissue windows, providing detailed visualization of the vertebral bodies and facet joints while confirming the absence of isthmic fractures, classifying the condition as degenerative rather than spondylolytic spondylolisthesis. This comparative imaging set illustrates the respective strengths of X-ray for alignment, MRI for neural elements and soft tissue, and CT for cortical bone integrity in the evaluation of lumbar degenerative diseases.

High-magnification light microscopy of a necrotic tissue biopsy stained with hematoxylin and eosin (H&E) reveals broad, nonseptate fungal hyphae with irregular, often wide-angle branching consistent with Mucorales (mucormycosis). The specimen shows extensive focal necrosis with loss of parenchymal architecture, irregular stromal disruption, and sparse neutrophilic and lymphohistiocytic inflammatory infiltrate. Within necrotic zones, thick-walled hyphae measuring approximately 5–20 μm in diameter traverse the tissue, displaying paucity of septa and occasional right-angle or variable-angle branching. The background demonstrates vascular congestion and occasional hyaline fungal elements; occasional sporangia are not clearly visible. The appearance is highly suggestive of invasive zygomycosis in an immunocompromised host or poorly controlled diabetes. Clinically important features include the need for rapid antifungal therapy (liposomal amphotericin B or amphotericin B), urgent surgical debridement, and correction of underlying acidosis or immunosuppression. Differential diagnosis includes Aspergillus species (septate hyphae with acute-angle branching), Fusarium, and other mould infections; however, septation and branching patterns help distinguish. The observation supports a diagnosis of fungal invasion in necrotic tissue, correlating with systemic signs of infection. In microbiology, culture and molecular assays can confirm genus. Utility: educational reference for histopathology, diagnostic pathology, and fungal infection management.

Imaging modality with technique details: Grocott methenamine silver stain applied to tissue biopsy. Light microscopy. The image shows a granulating necrotic focus with scattered, irregular thick fungal hyphae visible against a pale background. Hyphae are broad and variably wide, with intermittent septation and irregular, snake-like contours. The stain accentuates fungal cell walls in dark pigment (black/brown) on the eosinophilic necrotic tissue and inflammatory debris. The surrounding tissue demonstrates necrosis with sparse inflammatory cells. The morphological pattern is compatible with invasive molds; presence of hyphae within necrotic debris suggests tissue invasion. Distinguishing features include broad, nonseptate or pauci-septate hyphae with wide branching, a classic clue for Mucorales (mucormycosis); in contrast, Aspergillus would typically show narrow, septate hyphae with acute angle branching. Clinical correlation is essential given risk factors such as diabetes, neutropenia, or immunosuppression. The diagnostic significance lies in early recognition of invasive fungal infection to guide prompt antifungal therapy liposomal amphotericin B and surgical debridement where appropriate. Potential differential diagnoses include mucormycosis, aspergillosis, and other zygomycetes; PCR and culture should be performed for species-level identification. This image is a valuable educational resource for histopathology, infectious disease, and pathology training; courtesy of Dr. Katharina Glatz, University of Basel, Switzerland. Thank you.

**Imaging Modality:** Non-contrast Computed Tomography (NCCT) of the head.

**Imaging Modality:** Non-contrast axial Computed Tomography (CT) of the head.

A posteroanterior (PA) chest X-ray of an adult male demonstrating classic radiological features associated with Tetralogy of Fallot (TOF). The cardiac silhouette exhibits mild cardiomegaly and a characteristic 'boot-shaped' heart (coeur en sabot). This morphology is defined by an upturned, rounded cardiac apex, indicating right ventricular hypertrophy, and a concave pulmonary artery segment (pulmonary conus). The lung fields appear relatively oligemic, reflecting decreased pulmonary blood flow typical of right-to-left shunting or pulmonary stenosis. No acute pulmonary infiltrates or pleural effusions are visible. The costophrenic angles are clear. This diagnostic image is intended for medical students and clinicians to identify visual markers of cyanotic congenital heart disease and right ventricular pressure overload in an adult clinical presentation.

This diagnostic posteroanterior (PA) chest X-ray demonstrates the characteristic findings of Tetralogy of Fallot in a 21-year-old female patient. The image shows a well-centered view with adequate inspiratory effort. The primary finding is an increased cardiothoracic ratio with a distinctive 'boot-shaped' heart, also known as 'coeur en sabot.' This morphology is characterized by an upturned cardiac apex, resulting from significant right ventricular hypertrophy, and a concave pulmonary artery segment. The right heart border is notably prominent, indicating right atrial enlargement. Despite the history of surgical repair (including VSD closure and RV outflow tract reconstruction), these structural changes remain visible. The pulmonary vasculature appears normal, and the lung fields are clear without evidence of opacities, focal lesions, or pleural effusions. Sternal wires and surgical markers from prior cardiac procedures may be visible in the midline. The image serves as a classic educational example of chronic cardiac remodeling in congenital heart disease.

Imaging modality and technique: Light microscopy of Congo red-stained cardiac tissue examined under polarized light. Primary subject: Cardiac amyloidosis with amyloid deposition in the vascular wall. Specimen type: Cardiac tissue biopsy specimen. Imaging perspective: Polarized-light evaluation of Congo red–stained sections. Visual features: Irregular, eosinophilic, amorphous extracellular deposits confined to small- to mid-sized vessel walls within the myocardium; deposits appear as dense, salmon-pink material on routine brightfield and exhibit characteristic apple-green birefringence under polarized illumination. Diagnostic significance: Congo red positivity with apple-green birefringence confirms amyloid deposition in heart tissue, supporting a diagnosis of systemic amyloidosis with cardiac involvement. This finding is clinically relevant because myocardial amyloid deposition can cause restrictive cardiomyopathy with diastolic dysfunction and heart failure; identification guides systemic workup for AL (light-chain) vs ATTR (transthyretin) etiologies, and informs prognosis and treatment strategies. Differential considerations: Non-amyloid eosinophilic deposits or pigmentations would lack Congo red positivity and birefringence; however, the combination of Congo red staining and birefringence is consistent with amyloidosis. Clinical correlation: Correlate with echocardiography, cardiac MRI, serum free light chains, immunohistochemistry, and genetic testing as indicated.

A multi-panel figure illustrating diagnostic findings of systemic AL amyloidosis through microscopy and gross pathology. Panels A and B show a breast biopsy; Congo red staining (A) reveals pink amorphous stromal amyloid deposits, which demonstrate characteristic apple-green birefringence under polarized light (B). Panels C and D are gross photographs of an autopsied heart showing significant cardiomegaly and a thickened left ventricular myocardium, indicative of restrictive cardiomyopathy. Panel E displays a bone marrow microscopic section with hypercellularity and an abnormal plasma cell infiltrate. Panels F through I show myocardial autopsy sections; Congo red stain identifies widespread peri-myocytic (F) and vascular (H) pink amyloid deposits. Corresponding polarized light images (G, I) confirm these as amyloid through apple-green birefringence within the cardiac interstitium and vessel walls. This composite figure serves as an educational resource for identifying multisystemic amyloid infiltration and the underlying plasma cell dyscrasia.

This clinical photograph displays a lateral view of a patient's upper extremity and torso demonstrating classic features of plaque psoriasis. The focal point is the extensor surface of the elbow, which exhibits large, confluent, well-demarcated erythematous plaques. These plaques are characterized by a thick, micaceous, silvery-white scale, which is most prominent on the joint surface. Scattered across the surrounding forearm, upper arm, and lateral trunk are numerous smaller, discrete erythematous papules and plaques of varying sizes, representing a guttate or eruptive pattern. Some of these peripheral lesions show early scale formation, while others appear as simple erythematous macules. The distribution follows a typical pattern for chronic plaque-type psoriasis, emphasizing involvement of extensor surfaces. This image is an educational tool for dermatology, illustrating primary skin lesions including plaques, papules, and scales, and highlighting the hallmark morphological features used in the clinical diagnosis of psoriatic disease.

A clinical photograph of a 45-year-old male patient demonstrating moderate-to-severe plaque psoriasis on the lower back and elbow. The image shows a large, well-demarcated, erythematous plaque on the trunk characterized by thick, silvery-white micaceous scaling and a dry, fissured surface. Smaller satellite plaques are visible superior and lateral to the primary lesion. A similar thick, scaly plaque is noted on the extensor surface of the left elbow. The image includes annotations for clinical research monitoring: blue dashed squares delineate the target lesional site on the primary plaque for optical coherence tomography (OCT) scanning, while gray dashed squares indicate a perilesional control site on normal-appearing skin. This visual demonstrates the classic morphology of psoriasis vulgaris used for long-term therapeutic monitoring, with a reported PASI score of 10.8 and BSA of 10%.

This composite image illustrates the development of a low-cost, high-fidelity ultrasound training phantom for pediatric intussusception. Panel A shows a clinical photograph of a benchtop model consisting of silicone tubing submerged in a red-tinted gelatin and psyllium fiber matrix within a foil container. The tubing is coiled and invaginated to simulate loops of bowel and intussusception pathology. Panel B displays a diagnostic ultrasound image obtained from this phantom. The ultrasound reveals significant acoustic shadowing—characterized by dark vertical bands—emanating from the simulated bowel loops. This shadowing is an artifact likely caused by trapped air or dense material within the tubing, which prevents clear visualization of the classic 'target sign' or 'doughnut sign' typically sought in diagnostic imaging for intussusception. The model serves as an educational tool for emergency medicine and pediatric residents to practice bedside ultrasound techniques and recognize imaging pitfalls such as bowel gas artifacts.

Multi-modal clinical imaging of a nine-year-old pediatric patient with Henoch-Schönlein purpura (HSP) and ileoileal intussusception. Panel A (Plain Abdominal X-ray) shows focal bowel distention with gas in the right lower quadrant (black arrow). Panel B (Abdominal Ultrasound) demonstrates the classic 'target sign' or 'doughnut sign' in cross-section, indicative of intestinal invagination. Panels C and D (Axial CT, non-contrast and contrast-enhanced) reveal the site of intussusception with thickened intestinal walls forming a target sign (white arrow). Associated findings include enlarged para-aortic lymph nodes (black arrows) and free peritoneal fluid (curved arrow) around the liver and intestinal loops. These images illustrate the diagnostic workup for acute abdominal pain in children with systemic vasculitis, highlighting the transition from non-specific radiography to definitive cross-sectional imaging (US and CT) for identifying mechanical complications like intussusception and associated lymphadenopathy.

Diagnostic Image: This 12-lead electrocardiogram (ECG) demonstrates atrial flutter with a 2:1 atrioventricular (AV) conduction ratio. The tracing shows highly regular atrial activity with a characteristic sawtooth morphology. In the inferior leads (II, III, and aVF), the flutter waves are distinctly positive (upright), while in lead V1, the flutter waves exhibit a negative (inverted) polarity. This specific polarity pattern—upright flutter waves in the inferior leads and inverted in V1—is diagnostic of clockwise typical atrial flutter (atypical by counter-clockwise standards). The QRS complexes are regular and narrow, occurring at approximately half the frequency of the atrial rate (atrial rate ~300 bpm; ventricular rate ~150 bpm). In the precordial leads V4-V6, the QRS and T-wave morphologies are preserved, although discrete P waves are replaced by the undulating flutter baseline. The image illustrates a classic supraventricular tachycardia frequently encountered in cardiology and emergency medicine, serving as an educational example of macro-reentrant atrial rhythms.

A 12-lead electrocardiogram (ECG) recorded at a standard paper speed of 25 mm/s, demonstrating a narrow complex supraventricular tachycardia. The primary finding is atrial flutter with a 2:1 atrioventricular (AV) conduction ratio, resulting in a ventricular rate of approximately 150 beats per minute. Distinctive 'sawtooth' flutter waves (F-waves) are most prominent in the inferior leads (II, III, and aVF), characterized by negative deflections without an intervening isoelectric baseline. In the precordial leads V1-V3, the flutter waves appear more upright or biphasic. The QRS complexes are regular and maintain a consistent morphology and narrow duration, indicating normal ventricular depolarization following the 2:1 conduction from the atria. This tracing is a classic educational example used to distinguish atrial flutter from sinus tachycardia or atrial fibrillation in the context of regular narrow-complex tachycardia.