Cutaneous Syncytial Myoepithelioma: An Uncommon and Distinct Variant of Cutaneous Epithelioid Neoplasm.

BACKGROUND: Cutaneous syncytial myoepithelioma (CSM) is an uncommon and distinct variant of cutaneous myoepithelioma. We aim to present a case of CSM to enhance the recognition of this unique variant, encompassing its clinical characteristics, histopathological features, immunohistochemical staining, and therapeutic approaches. CASE PRESENTATION: A 10-year-old girl presented with a dome-shaped nodule located on the skin of her left medial distal arm. Microscopic examination of the skin biopsy revealed a well-defined dermal nodular lesion, surrounded by an epidermal collarette. Tumor cells were composed of epithelioid to spindle-shaped cells with round-to-oval nuclei, small nucleoli, and abundant eosinophilic cytoplasm with a syncytial-like growth pattern. A moderate degree of nuclear pleomorphism was noted. Mitotic activity was not prominent. Immunohistochemical staining revealed positive staining for epithelial membrane antigen, GLUT1, collagen IV, and S100. Smooth muscle actin, CD10, and CD68 showed patchy positivity. CD31, CD34, p63, SOX10, anaplastic lymphoma kinase (ALK), glial fibrillary acidic protein, pankeratin (AE1/AE3/PCK26), Melan-A, and CD1a were negative. Fluorescence in situ hybridization targeting TFE3 and ALK genes was negative. The differential diagnosis included ALK-negative epithelioid cell histiocytoma, epithelioid perineurioma, and CSM. Based on the above findings, a diagnosis of CSM was rendered. DISCUSSION: CSM is a benign cutaneous neoplasm composed of sheets of histiocytoid or short spindle cells with pale eosinophilic cytoplasm with a syncytial-like growth pattern. Clinically, CSM often presents as a painless, slow-growing nodule or plaque in a broad anatomical distribution with a preference for the distal extremities.. CSM is characteristically positive for epithelial membrane antigen (EMA) and S100 protein and negative for keratins. In challenging cases, molecular testing for EWSR1 gene rearrangement and EWSR1-PBX3 gene fusion aid in confirming the diagnosis. CONCLUSIONS: The histologic features of CSM present a unique set of challenges posing a diagnostic dilemma, as they can bear resemblance to a range of benign and malignant cutaneous neoplasms including ALK-negative epithelioid cell histiocytoma, epithelioid perineurioma, malignant or nevoid melanoma, and epithelioid sarcoma. An accurate diagnosis is crucial for guiding proper clinical management considering that this entity typically demonstrates an excellent prognosis following a complete surgical excision.

Erythema Multiforme-Like Fixed Drug Eruption During Azathioprine and Hydroxychloroquine Treatment for Systemic Lupus Erythematosus Mimicking Rowell Syndrome: A Rare and Challenging Clinical Scenario.

Background. Fixed drug eruption and Rowell syndrome stand as intriguing entities with overlapping clinical and pathological features. Case Presentation. A 32-year-old female patient presented with a tender and pruritic rash on the left upper chest for 3 days. Clinical examination revealed a flaring rash on the chest, under her left eye, tongue, and lips. The patient had a significant past medical history of systemic lupus erythematous with positive (ANA, Sm, dsDNA, ribosomalP, RNP) antibodies, hypocomplementemia, inflammatory arthritis, discoid lupus, leukopenia, thrombocytopenia, and immune thrombocytopenic purpura, and avascular necrosis affecting both hips and her right knee. At the time of presentation, the patient was on azathioprine 150 mg daily and hydroxychloroquine 200 mg twice daily. Skin biopsy of the left upper chest revealed interface dermatitis with necrotic keratinocytes at the dermal-epidermal junction. Superficial and, in some areas, deep perivascular and peri adnexal lymphocytic infiltrates were observed, accompanied by eosinophils. CD123 staining highlighted 16% of the inflammatory cells. Direct Immunofluorescence for IgG, IgA, IgM, C3, and fibrinogen revealed positive linear basement membrane staining for IgG and fibrinogen, with no significant staining for the remaining immunoreactants. Considering the patient's history of medicine usage, and negative SS-A and SS-B antibody, a fixed drug eruption was favored. Discussion. This article discusses the clinical presentations, pathophysiological mechanisms, and diagnostic criteria for fixed drug eruption and Rowell syndrome. Conclusion. Awareness of the distinct clinical and histopathologic features of fixed drug eruption and Rowell syndrome, particularly when sharing cutaneous manifestations, underscores the importance of a comprehensive diagnostic approach and laboratory testing.

Extra-Ocular Sebaceous Carcinoma in Situ of the Arm of an Elder Male: An Unusual Presentation in an Atypical Location.

Background. Sebaceous carcinoma in situ outside the ocular region is an exceedingly uncommon. It is an intraepidermal neoplasm originating from sebaceous glands limited to the epidermis with no invasion into the underlying dermis or beyond. Although sebaceous carcinoma in situ is predominantly observed in ocular regions, particularly the eyelids, instances of its occurrence in extraocular locations are infrequent, with only a limited number of examples reported in the literature. Case Presentation. A 63-year-old man presented with a left posterior arm lesion. Microscopic examination revealed a proliferation of poorly differentiated atypical neoplastic sebocytes confined to the epidermis with pleomorphic nuclei, prominent nucleoli, and clear cell changes. The neoplastic cells demonstrated positive staining for adipophilin, androgen receptor, epithelial membrane antigen, P63, BerEP4, and keratin 7. Microsatellite instability markers showed preserved nuclear staining for MLH1, PMS2, MSH2, and MSH6. A definitive diagnosis of sebaceous carcinoma in situ was rendered. Discussion. The distinctive histopathologic characteristics typically involve the presence of atypical sebaceous cells confined within the epidermis. Atypical cells often exhibit enlarged nuclei, increased mitotic activity, and prominent nucleoli. A panel of epithelial membrane antigen, adipophilin, and androgen receptors is essential for ensuring an accurate diagnosis. Conclusion. This report underscores the importance of considering sebaceous carcinoma in situ in diagnosis in atypical locations, emphasizing the need for a comprehensive histopathologic examination and immunohistochemical staining panel. This article aims to demonstrate the rarity of sebaceous carcinoma in situ in extraocular sites to broaden our understanding of its diverse clinical presentations.

Evaluation of programmed cell death ligand 1 expression in a contemporary cohort of penile squamous cell carcinoma and its correlation with clinicopathologic and survival parameters: A study of 134 patients.

OBJECTIVES: Penile squamous cell carcinomas (PCs) are rare malignancies with a dismal prognosis in a metastatic setting; therefore, novel immunotherapeutic modalities are an unmet need. One such modality is the immune checkpoint molecule programmed cell death ligand 1 (PD-L1). We sought to analyze PD-L1 expression and its correlation with various clinicopathologic parameters in a contemporary cohort of 134 patients with PC. METHODS: A cohort of 134 patients with PC was studied for PD-L1 immunohistochemistry. The PD-L1 expression was evaluated using a combined proportion score with a cutoff of 1 or higher to define positivity. The results were correlated with various clinicopathologic parameters. RESULTS: Overall, 77 (57%) patients had positive PD-L1 expression. Significantly high PD-L1 expression was observed in high-grade tumors (P = .006). We found that 37% of human papillomavirus (HPV)-associated subtypes and 73% of other histotype tumors expressed PD-L1, while 63% of HPV-associated tumors and 27% of other histotype tumors did not (odds ratio, 1.35; P = .002 when compared for HPV-associated groups vs all others). Similarly, PD-L1-positive tumors had a 3.61-times higher chance of being node positive than PD-L1-negative tumors (P = .0009). In addition, PD-L1 high-positive tumors had a 5-times higher chance of being p16ink4a negative than PD-L1 low-positive tumors (P = .004). The PD-L1-positive tumors had a lower overall survival and cancer-specific survival than PD-L1-negative tumors. CONCLUSIONS: Overall, PD-L1 expression is associated with high-grade and metastatic tumors. Lower PD-L1 expression is observed more frequently in HPV-associated (warty or basaloid) subtypes than in other, predominantly HPV-independent types. As a result, PD-L1 positivity, including higher expression, portends lower overall and cancer-specific survival. These data provide a rational for further investigating PD-L1-based immunotherapeutics in PC.

Cutaneous Atypical Fibroxanthoma With Osteoclast-Like Giant Cell: A Rare but Diagnostic Pitfall.

BACKGROUND: Atypical fibroxanthoma (AFX) is a dermal-based, low-grade neoplasm with no specific lineage of differentiation. The occurrence of AFX with osteoclast-like giant cells is exceptionally rare. Less than 20 cases have been reported in the literature. CASE PRESENTATION: A 77-year-old man with a medical history of multiple basal and squamous cell carcinomas of the skin, presented with a progressively growing erythematous nodule on the sun-damaged right central parietal scalp. A shave biopsy showed a dermal spindle cell proliferation accompanied by numerous osteoclast-like multinucleated giant cells and predominant atypical mitotic figures. The immunohistochemical staining showed a diffuse positive staining for CD68 and SMA, patchy staining for CD10, and negative staining for SOX-10, pan-cytokeratin, CK5/6, S100, CD34, and desmin. The tumor was completely excised with negative margins. A subsequent follow-up over a period of 13 months showed no recurrence. CONCLUSION: Distinguishing AFX with osteoclast-like giant cells from both malignant and benign skin lesions with osteoclast-like giant cells is crucial. Although AFX tumors display worrisome malignant histologic features, most cases have a favorable prognosis with a local recurrence rate below 5% and exceedingly rare metastasis.

Does Immunohistochemistry Add to Morphology in Differentiating Trichoepithelioma, Desmoplastic Trichoepithelioma, Morpheaform Basal Cell Carcinoma, and Microcystic Adnexal Carcinoma?

BACKGROUND: The distinction among cutaneous basaloid neoplasms such as trichoepithelioma (TE), desmoplastic trichoepithelioma (DTE), morpheaform basal cell carcinoma (MBCC), and microcystic adnexal carcinoma (MAC) can be difficult, especially in superficial biopsies. As the treatment plan of each entity is different, accurate characterization is important for appropriate management. While TE and DTE are benign neoplasms with indolent behavior, MBCC and MAC are typically locally aggressive. The expression of several recently described immunohistochemical (IHC) markers, including p40, IMP3, and ProEx C, has not been adequately established in cutaneous neoplasms. We explored the potential utility of a broad IHC panel, including previously reported and novel markers to differentiate TE, DTE, MBCC, and MAC. DESIGN: A total of 35 archival cases [TE (n=14), DTE (n=9), MBCC (n=6), and MAC (n=6)] were stained with 9 IHC markers: p40, IMP3, ProEx C, p16, CK20, Ki-67, androgen receptor, D2-40, and beta-catenin. Tumors with >5% immunoreactivity were scored as positive. The intensity was scored on a scale from 1+ to 3+. The pattern of positivity- nuclear, cytoplasmic, membranous, or in combination; peripheral or central distribution with lesion was also recorded. RESULTS: CK20 (in contrast to prior studies) and IMP3 were negative in all cases. Likewise, with the exception of one case of TE, androgen receptor showed no immunoreactivity in all categories. No significant difference was observed in the expression of beta-catenin, p16, ProEx C, and p40 among the four groups of cutaneous neoplasms. The mean Ki-67 labeling index for MBCC (8%) was slightly higher than DTE (3%). Interestingly, the proliferation index for TE (15%) was significantly higher than that of MBCC. All six cases of MAC and 36% of TEs expressed D2-40; neither the MBCC nor DE cases showed D2-40immunoreactivity. Also, we confirmed the previously published observation of scattered CK20 positive Merkel cells in the epidermis of all cases of DTE; whereas, no Merkel cells were identified in MBCC and MAC cases. CONCLUSIONS: Except Ki-67, our IHC panel showed no significant added diagnostic utility of IHC in discriminating among TE, DTE, MBCC, and MAC. Among the four cutaneous neoplasms, DTE and MBCC show a small but discernible difference in Ki-67.

Association of Clinical Signs, Host Biomarkers and Etiology With Radiological Pneumonia in Bhutanese Children.

Diagnosing pneumonia and identifying those requiring antibiotherapy remain challenging. Chest radiographs (CXR) are often used as the reference standard. We aimed to describe clinical characteristics, host-response biomarkers and etiology, and assess their relationship to CXR findings in children with pneumonia in Thimphu, Bhutan. Children between 2 and 59 months hospitalized with WHO-defined pneumonia were prospectively enrolled and classified into radiological endpoint and non-endpoint pneumonia. Blood and nasopharyngeal washing were collected for microbiological analyses and plasma levels of 11 host-response biomarkers were measured. Among 149 children with readable CXR, 39 (26.2%) presented with endpoint pneumonia. Identification of respiratory viruses was common, with no significant differences by radiological outcomes. No clinical sign was suggestive of radiological pneumonia, but children with radiological pneumonia presented higher erythrocyte sedimentation rate, C-reactive protein and procalcitonin. Markers of endothelial and immune activation had little accuracy for the reliable identification of radiological pneumonia.

p53 and p16ink4a As Predictive and Prognostic Biomarkers for Nodal metastasis and Survival in A Contemporary Cohort of Penile Squamous Cell Carcinoma.

BACKGROUND: Human papilloma virus (HPV) infection is implicated in a proportion of invasive squamous cell carcinoma of the penis (PC). A subset of PC involves dysregulation of the p53 pathway. HPV in situ hybridization (ISH) and p16ink4a positivity are surrogate markers for HPV infection, and p53 immunohistochemistry (IHC) denotes abnormality in the p53 pathway. There remains an ambiguity with regard to the contribution of both the pathways in the prognosis of PC. We sought to analyze the clinicopathologic characteristics of a cohort of Indian PC patients with respect to p16 ink4a and p53 expression. PATIENTS AND METHODS: A cohort of 123 PC patients was studied for p16ink4aand p53IHC and HPVISH. The results of these biomarkers were correlated with various clinicopathologic parameters. RESULTS: p16ink4a and HPV ISH were positive in 47% and 53% of the tumors, respectively. The proportion of warty, basaloid, or mixed warty-basaloid tumor subtypes showed significant p16ink4apositivity (P < .0001) compared to other subtypes. Twenty-eight patients were dual negative (p53- /p16ink4a-), 32 were dual positive (p53+/p16ink4a+), 38 were p53+/p16ink4a-, and 25 were p53-/p16ink4a +. In patients where p16ink4a was negative, a p53-positive phenotype had a higher propensity for lymph node metastases (OR, 5.42; 95% CI, 1.75-16.80; P = .003). Similarly, p53 positivity dictates nodal involvement in the p16ink4a-positive subset of tumors (OR, 5.00; 95% CI, 1.23-20.17; P = .024). On multivariate analyses, pathologic subtypes (warty, warty-basaloid, and basaloid) (P < .0001), p16ink4aexpression (P < .0001), and absence of nodal metastasis (P < .0001) were significant predictors of improved overall (OS) and cancer specific survival (CSS). In Kaplan-Meier analysis, the OS was significantly longer in patients with p16ink4a + tumors (P < .0001), as was the CSS (P < .0001). Patients with dual positive tumors had a significantly higher OS (P < .001) and CSS (P = .012), in the entire cohort. In the node positive patients, dual positivity was associated with significantly higher OS (P < .0001); however, the median CSS for p53+/p16ink4a+tumors were not significantly different compared to p53- /p16ink4a- tumors (P = .064), although there was a trend towards improved CSS. CONCLUSIONS: There is a strong concordance between p16ink4aIHC and HPV ISH results. p16ink4a status is an independent predictor of survival (OS and CSS) in our cohort of PCs. p53 is a predictor of nodal metastasis irrespective of p16 status. Dual positive tumors have a significantly better outcome in comparison to dual negative tumors.

Comparison of epidermal growth factor receptor mutation detection turnaround times and concordance among real-time polymerase chain reaction, high-throughput next-generation sequencing and the Biocartis Idylla™ platforms in non-small cell lung carcinomas.

OBJECTIVES: Activating mutations in the tyrosine kinase domain of the epidermal growth factor receptor (EGFR) gene of non-small cell lung carcinomas (NSCLC) can be targeted by the tyrosine kinase inhibitors. A number of molecular diagnostic platforms are used to detect actionable targets in the exon(s) 18, 19, 20, and 21 of the EGFR gene. The Idylla™ system (Biocartis, Mechelen, Belgium) is a relatively novel technique and is unique in integrating both sample processing and real-time polymerase chain reaction (RT-PCR) in a single cartridge. We sought to conduct this study to compare the turnaround time (TAT) and concordance of Idylla™ system with the conventional RT-PCR and next-generation sequencing (NGS) for EGFR mutation detection. METHODS: In this retrospective analysis, 38 formalin-fixed, paraffin-embedded NSCLC tissue blocks with known NGS results by Ion Torrent™ S5 NGS platform were retested by the RT-PCR and Idylla™ platforms. RESULTS: A total of 15 of 38 (39.4 %) tumors that showed various EGFR mutations by NGS and conventional RT-PCR techniques were subjected to the Idylla™testing. These cases satisfied the specimen adequacy criteria of at least 10 % tumor cells for the testing. The mutations detected by the NGS were also detected by the Idylla™ testing. However, NGS identified additional 3 mutations in 3 cases, involving T709 V (exon 18, n = 1) and V774 M (exon 20, n = 2). The tumors with wild type EGFR on NGS did not have any actionable mutation detected by the Idylla™. Average EGFR testing TAT by Idylla™ was only 7.2 h (4-12 hours), as compared to conventional RT-PCR taking 54 h (31-79 hours) and NGS requiring 10.7 days (7.1-14 days). The actual procedure time by conventional RT-PCR was 24 h, NGS was 6.5 days, and Idylla™ was only 3 h. CONCLUSIONS: In summary, the Idylla™EGFR testing is an efficient, rapid, and fairly simple tool that can be used in the routine molecular laboratory with limited expertise and infrastructure and using the lowest amount of tissue material.

Immunohistochemical Markers With Potential Diagnostic, Prognostic, and Therapeutic Significance in Uterine Carcinosarcoma: A Clinicopathologic Study of 43 Cases.

Uterine carcinosarcomas (UCS) are rare and highly aggressive tumors. Although it is currently accepted that the majority of UCS are metaplastic carcinomas, their aggressive behavior is unparalleled to that of any other high-grade endometrial neoplasms. Therefore, the search for the distinct immunohistochemical and molecular features that could help in the development of new treatment strategies continues. We evaluated the expression of PDL-1, growth hormone releasing hormone receptor, p53, WT1, PAX-8, estrogen receptor, HNF-1, and mismatch repair proteins in 43 UCS. Tumors were selected from the archives of the Magee-Womens Hospital University of Pittsburgh Medical Center Department of Pathology. Seventeen were stage I, 4 were stage II, 15 were stage III, and 7 were stage IV. The median age was 67 yr and median overall survival was 3.2 yr. Immunostaining for PAX8, HNF-1, and estrogen receptor showed statistically significant difference between epithelial and stromal components. Expression of p53 was significantly associated with clinical high stage, but other markers did not correlate with stage or survival. Immunostaining for programmed death ligand-1 was strongly positive in 30 UCS (70%), including 24 cases with tumor cell positivity, 12 cases with tumor cell and tumor-infiltrating immune cell positivity, and 6 cases with tumor-infiltrating immune cell positivity only. Of 27 tumors tested for mismatch repair expression, 12 (44%) showed loss of expression, 7 of which were PDL-1 positive. Growth hormone releasing hormone receptor was positive in 38 tumors (88%) and predominantly expressed in the epithelial component. The range of positivity for programmed death ligand-1 and growth hormone releasing hormone receptor suggests a possible potential adjuvant treatment that may be considered for UCS.

Clinical performance of the aptima HPV assay in 4196 women with positive high-risk HPV and ASC-US cytology: A large women hospital experience.

BACKGROUND: Despite Aptima assay as the latest US Food Drug Administration (FDA)-approved high-risk human papillomavirus (hrHPV) test has been implemented as an adjunct in cervical cancer screening for years, histological follow-up data remain limited with respect to its performance in women with ASC-US Pap tests and positive hrHPV results. METHODS: Cases with results of ASC-US cytology and positive hrHPV by Aptima assay during the period 06/ 2015-02/2017 were retrieved from archived pathology reports. Immediate histological follow-up results were analyzed within 6 months interval after cotesting. RESULTS: Among 4196 women with ASC-US Pap tests and positive hrHPV, 51.1% of them had the immediate histological follow-up within 6 months. With positive Aptima hrHPV as the adjunct, 46.5% (95%CI 46.2-46.8) of ASC-US women were found to have cervical intraepithelial neoplasia type 1 (CIN1); 8.8% (95%CI 8.1-9.5) women were detected CIN2+ lesion including eight adenocarcinoma in-situ (AIS)s. CIN2+ detection rates were highest in women under 25 (15.4%, n = 65), when comparison with different age cutoffs, younger age women had higher CIN2+ lesion detection rate than that in older group (P <.01). CONCLUSION: This is by far one of the largest retrospective studies to analyze the histological follow-up results of ASC-US women with positive hrHPV tested by Aptima hrHPV mRNA assay. The results indicated that younger women with ASC-US and positive hrHPV testing have highest risk of developing high grade CIN lesions as compared to the older women. Lastly, with positive HPV as the adjunct, 55.3% (1186/2145) of ASC-US women will result in the positive finding on histological follow-up.

Primary round cell sarcomas of the urinary bladder with EWSR1 rearrangement: a multi-institutional study of thirteen cases with a review of the literature.

Primary Ewing sarcoma (ES) of the urinary bladder is a rare and aggressive small blue round cell malignant neoplasm associated primarily with translocation involving EWSR1 and FLI1 genes located in the 22nd and 11th chromosomes, respectively. To date, 18 cases have been published in the literature as single-case reports, based chiefly on CD99 positivity (17 patients). Molecular confirmation by fluorescence in situ hybridization was performed in 9 patients, and FLI1 immunohistochemical (IHC) analysis was not performed in any of these published cases. Herein, we present thirteen patients of more comprehensive primary round cell sarcomas of the urinary bladder with EWSR1 rearrangement. Clinicopathologic parameters including demographics; clinical presentation; histopathologic, IHC, and molecular profiles; and management and follow-up data of 13 patients with primary round cell sarcomas with EWSR1 rearrangement (Ewing family of tumor) of the urinary bladder were analyzed. The studied patients (n = 13) included 6 females and 7 males; their age ranged from 4 years to 81 years (median = 30 years). The most common clinical presentation was hematuria (n = 7), followed by hydronephrosis (n = 2, one with renal failure). The tumor size ranged from 2.9 cm to 15 cm in maximum dimension. Conventional ES architecture and histology was observed in 6 cases, and diverse histology was observed in 7 cases (adamantinomatous pattern [n = 1], alveolar pattern [n = 1], ganglioneuroblastoma-like pattern [n = 2], and small cell carcinoma-like pattern [n = 3]). All the tumors were muscle invasive (invasion into the muscularis propria). IHC analysis showed that all tumors expressed FLI1, CD99, and at least one neuroendocrine marker. Focal cytokeratin staining was positive in 2 patients, and RB1 was retained in all patients. EWSR1 rearrangement was seen in 12 of 12 tumors (in 12 patients) tested. A combined multimodal approach that included surgery with chemotherapy was instituted in all patients. Follow-up was available for 11 patients (ranging from 5 to 24 months). Six patients either died of disease (n = 3) or other causes (n = 3). Five patients were alive with metastases to the liver (n = 1), liver and lung (n = 2), liver and abdominal wall (n = 1), and kidney (n = 1). Based on our experience with the largest series to date and aggregate of the published data, ES/round cell sarcomas with EWSR1 rearrangement occurring in the bladder have bimodal age distribution with poor prognosis despite aggressive therapy. Owing to its rarity and age distribution, the differential diagnosis is wide and requires a systematic approach for ruling out key age-dependent differential diagnoses aided with molecular confirmation.

Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) and coronavirus disease 19 (COVID-19) - anatomic pathology perspective on current knowledge.

BACKGROUND: The world is currently witnessing a major devastating pandemic of Coronavirus disease-2019 (COVID-19). This disease is caused by a novel coronavirus named Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2). It primarily affects the respiratory tract and particularly the lungs. The virus enters the cell by attaching its spike-like surface projections to the angiotensin-converting enzyme-2 (ACE-2) expressed in various tissues. Though the majority of symptomatic patients have mild flu-like symptoms, a significant minority develop severe lung injury with acute respiratory distress syndrome (ARDS), leading to considerable morbidity and mortality. Elderly patients with previous cardiovascular comorbidities are particularly susceptible to severe clinical manifestations. BODY: Currently, our limited knowledge of the pathologic findings is based on post-mortem biopsies, a few limited autopsies, and very few complete autopsies. From these reports, we know that the virus can be found in various organs but the most striking tissue damage involves the lungs resulting almost always in diffuse alveolar damage with interstitial edema, capillary congestion, and occasional interstitial lymphocytosis, causing hypoxia, multiorgan failure, and death. A few pathology studies have also reported intravascular microthrombi and pulmonary thrombembolism. Although the clinical presentation of this disease is fairly well characterized, knowledge of the pathologic aspects remains comparatively limited. CONCLUSION: In this review, we discuss clinical, pathologic, and genomic features of COVID-19, review current hypotheses regarding the pathogenesis, and briefly discuss the clinical characteristics. We also compare the salient features of COVID-19 with other coronavirus-related illnesses that have posed significant public health issues in the past, including SARS and the Middle East Respiratory Syndrome (MERS).