Molecular Classification Outperforms Histologic Classification in Prognostication of High-grade Endometrial Carcinomas With Undifferentiated and Sarcomatous Components.

Since the establishment of 4 molecular subgroups of endometrial carcinoma (EC), there has been significant interest in understanding molecular classification in the context of histologic features and diagnoses. ECs with undifferentiated, spindle, and/or sarcomatous components represent a diagnostically challenging subset of tumors with overlapping clinical and histologic features. We examined the clinicopathologic, morphologic, immunohistochemical, and molecular features of these tumors identified in our institutions' pathology databases using immunohistochemistry and targeted sequencing. Disease-specific survival (DSS) and progression-free survival (PFS) were analyzed using Kaplan-Meier curves and log-rank tests. One hundred sixty-two ECs were included: carcinosarcomas (UCS; n=96), dedifferentiated/undifferentiated EC (DDEC/UDEC; n=49), and grade 3 endometrioid EC with spindled growth (GR3spEEC) (n=17). All molecular subgroups were represented in all histologic subtypes and included 12 (7%) POLE-mutated (POLEmut), 43 (27%) mismatch repair-deficient (MMRd), 77 (48%) p53-abnormal (p53abn), and 30 (19%) no specific molecular profile (NSMP) tumors. However, the molecular classification (irrespective of histologic diagnosis) was a significant predictor for both DSS (P=0.008) and P≤0.0001). POLEmut EC showed an excellent prognosis with no recurrences or deaths from the disease. MMRd tumors also showed better outcomes relative to NSMP and p53abn tumors. In conclusion, molecular classification provides better prognostic information than histologic diagnosis for high-grade EC with undifferentiated and sarcomatous components. Our study strongly supports routine molecular classification of these tumors, with emphasis on molecular group, rather than histologic subtyping, in providing prognostication.

Yolk Sac Differentiation in Endometrial Carcinoma: Incidence and Clinicopathologic Features of Somatically Derived Yolk Sac Tumors Versus Carcinomas With Nonspecific Immunoexpression of Yolk Sac Markers.

Endometrial somatically derived yolk sac tumors are characterized by yolk sac morphology with AFP, SALL-4, and/or Glypican-3 immunoexpression. Yolk sac marker expression, however, is not limited to tumors with overt yolk sac histology. Three hundred consecutive endometrial malignancies were assessed for immunomarkers of yolk sac differentiation. Of these, 9% expressed ≥1 yolk sac marker, including 29% of high-grade tumors. Only 3 (1%) met morphologic criteria for yolk sac differentiation; these were originally diagnosed as serous, high-grade NOS, and dedifferentiated carcinoma. Two were MMR-intact and comprised exclusively of yolk sac elements, while the dedifferentiated case was MMR deficient and had a background low-grade endometrioid carcinoma; this case also showed BRG1 loss. All 3 were INI1 intact. Nonspecific yolk sac marker expression was seen in 14 carcinosarcomas, 4 endometrioid, 2 serous, 1 clear cell, 1 dedifferentiated, 1 mixed serous/clear cell, and 1 mesonephric-like carcinoma. INI1 was intact in all cases; one showed BRG1 loss. Twenty were MMR-intact, and 4 were MMR deficient. All MMR-deficient cases with yolk sac marker expression, both with and without true yolk sac morphology, had no evidence of residual disease on follow-up, whereas 82% of MMR-intact cases developed recurrent/metastatic disease. In summary, endometrial somatically derived yolk sac tumors were rare but under-recognized. While AFP immunostaining was specific for this diagnosis, Glypican-3 and SALL-4 expression was seen in a variety of other high-grade carcinomas. INI1 loss was not associated with yolk sac morphology or immunomarker expression in the endometrium, and BRG1 loss was rare. All patients with MMR-deficient carcinomas with yolk sac immunoexpression +/- morphology were disease-free on follow-up, whereas the majority of MMR-intact cancers showed aggressive disease.

Transitioning From Trainee to Practicing Pathologist: A Prospective Multi-institutional Survey of the Challenges Early Career Anatomic Pathologists Encounter When Entering Independent Practice.

CONTEXT.­: Pathology training programs generally prepare graduates well for the workforce, but there may be other aspects to navigating a job that make the transition from being a trainee to a practicing pathologist challenging. OBJECTIVE.­: To identify perceived challenges of independent practice for early career pathologists and assess how these impressions evolve throughout their first year. DESIGN.­: A survey was distributed to 12 anatomic pathology fellows from 4 institutions near the end of their final training year, and 6 months and 1 year after starting their first job. The surveys queried participants' comfort level with signing out cases independently and interacting with colleagues/trainees via Likert attitude scale questions with free-text segments to elaborate on challenges experienced. RESULTS.­: The response rate to all 3 surveys was 100%. Confidence and comfort level with different aspects of independent sign-out increased incrementally over time. Main challenges encountered at 6 months included a high case load, signing out cases in areas outside of their subspecialty, time management, balancing teaching while signing out, laboratory issues, and developing relationships with clinicians. At 12 months, main challenges included time management, high case load, understaffing, laboratory issues, and signing out cases in areas outside of their subspecialty. CONCLUSIONS.­: This study identified real-time challenges faced by those adjusting to their first year of independent practice. By gaining a better understanding of the factors that make this transition challenging, we can find tailored ways to support our early career pathologists.

Updates in the Use of Immunohistochemical Stains in Breast and Gynecologic Pathology.

CONTEXT.­: The use of immunohistochemical stains in breast and gynecologic pathology has become increasingly complex, with various diagnostic, prognostic, and predictive applications. OBJECTIVE.­: To provide an update and review of immunohistochemical stains used in the practice of breast and gynecologic pathology. Established and new entities are reviewed, with descriptions of histomorphology and immunohistochemical staining patterns and discussion of interpretive pitfalls. DATA SOURCES.­: Data were obtained from review of the English-language literature and firsthand experience of the authors in breast and gynecologic pathology. CONCLUSIONS.­: Many entities in breast and gynecologic pathology benefit from evaluation with various immunohistochemical stains. These studies not only aid in the diagnosis and staging of tumors but also can provide prognostic and predictive information. Updated guidelines for recommended ancillary studies such as mismatch repair, p53, and human epidermal growth factor receptor 2 (HER2) studies in endometrium, as well as estrogen and progesterone receptors and HER2 in breast, are discussed. Finally, the use and interpretation of established and novel immunohistochemical stains are discussed in various breast and gynecologic malignancies.

Dichotomous ovarian cancer-initiating potential of Pax8+ cells revealed by a mouse genetic mosaic model.

Different cellular compartments within a tissue present distinct cancer-initiating capacities. Current approaches to dissect such heterogeneity require cell-type-specific genetic tools based on a well-understood lineage hierarchy, which are lacking for many tissues. Here, we circumvented this hurdle and revealed the dichotomous capacity of fallopian tube Pax8+ cells in initiating ovarian cancer, utilizing a mouse genetic system that stochastically generates rare GFP-labeled mutant cells. Through clonal analysis and spatial profiling, we determined that only clones founded by rare, stem/progenitor-like Pax8+ cells can expand on acquiring oncogenic mutations whereas vast majority of clones stall immediately. Furthermore, expanded mutant clones undergo further attrition: many turn quiescent shortly after the initial expansion, whereas others sustain proliferation and manifest a bias toward Pax8+ fate, underlying early pathogenesis. Our study showcases the power of genetic mosaic system-based clonal analysis for revealing cellular heterogeneity of cancer-initiating capacity in tissues with limited prior knowledge of lineage hierarchy.

HER2 Overexpression and Amplification in Uterine Carcinosarcomas With Serous Morphology.

Uterine carcinosarcoma (UCS) is an aggressive malignancy with few treatment options. A recent clinical trial has shown an increase in progression-free survival in patients with human epidermal growth factor receptor 2 (HER2)-positive serous endometrial carcinomas treated with anti-HER2-targeted therapies. Few studies have evaluated HER2 expression/amplification in UCS. Similar to serous endometrial carcinoma, the majority of UCS have TP53 mutations and a serous epithelial component, suggesting that UCS may show similar rates of HER2 positivity and therapeutic response. Therefore, we evaluated HER2 expression/amplification in a cohort of UCS over a 5-year period. HER2 immunohistochemistry (IHC) and chromogenic in situ hybridization were performed on tissue microarray and whole tissue sections and scored according to the most recent clinical trial recommendations. Three of 48 UCS (6%) had strong (3+) HER2 IHC expression, and 3 cases (6%) were equivocal (2+). Seven cases (15%) had HER2 amplification by chromogenic in situ hybridization, including all 3 with overexpression and 2 that were equivocal by IHC. Mismatch repair (MMR) protein, p53, and programmed cell death-ligand 1 (PD-L1) expression status was obtained from prior whole section analyses. All HER2-positive cases had a serous morphology and aberrant p53 expression. Only minimal PD-L1 expression was seen in the HER2-positive cases, and none had MMR loss. A subset of UCS with serous morphology have overexpression and/or amplification of HER2, which may predict response to HER2-targeted therapies. HER2-positive UCS may be less susceptible to immune checkpoint inhibition as they uncommonly show MMR deficiency and/or strong PD-L1 expression. Thus, HER2-targeted therapies could be of clinical utility in a subset of UCS without other adjuvant treatment options.

Mesonephric-like Endometrial Carcinoma: Results From Immunohistochemical Screening of 300 Endometrial Carcinomas and Carcinosarcomas for This Often Overlooked and Potentially Aggressive Entity.

Mesonephric-like endometrial carcinoma is a rare but frequently misclassified and aggressive malignancy. KRAS mutations, limited estrogen receptor (ER) expression, and TTF-1, GATA3, and luminal CD10 expression are described in these tumors, but an immunohistochemistry-based screening approach has not been studied. We assessed 300 endometrial carcinomas/carcinosarcomas to ascertain the specificity of TTF-1/GATA3/luminal CD10 expression with or without ER staining for this diagnosis. Next-generation sequencing and morphologic review were performed on screen-positive cases. In all, 3% (9/300) were TTF-1+; 2 coexpressed GATA3. No cases expressed luminal CD10 or GATA3 in isolation. Two TTF-1+/ER- cases, one of which was also GATA3+, were reclassified as mesonephric-like based on morphology and molecular results (KRAS mutations without mismatch repair deficiency, TP53 mutations, or PTEN mutations): these represented 0.7% of all cases (2/300). The reclassified cases were originally diagnosed as grade 1 and 2 endometrioid carcinoma, and the latter had pulmonary metastases and pelvic recurrences. Six TTF-1+ cases retained their original serous (3) and endometrioid (3) diagnoses; 1 was reclassified as dedifferentiated. All had negative or low ER. KRAS mutations were identified in 4 TTF-1+ non-mesonephric-like cases, including 1 serous and 1 grade 3 endometrioid with p53 abnormalities, 1 mismatch repair-deficient endometrioid with a complex molecular profile, and 1 endometrioid with mucinous differentiation. These findings suggest that TTF-1 and ER are good first-line screens for mesonephric-like carcinoma, but caution that a TTF-1+/ER- immunoprofile is not specific, even in the setting of KRAS mutations. A final diagnosis of mesonephric-like carcinoma requires integration of morphologic and immunohistochemical features, with molecular support when relevant.

Global Health Education in Pathology Residency.

OBJECTIVES: Pathology and laboratory medicine (PALM) services in low- and middle-income countries are essential to combat the increasing prevalence of cancer in addition to providing documentation of cancer types and trends for future allocation of public health resources. There are many ways PALM as a whole can engage on the global health front. This study summarizes the efforts and results of a global health educational and clinical elective for pathology residents in Quetzaltenango, Guatemala. METHODS: Pathology residents led and implemented the project, working alongside an in-country pathologist and project collaborator to instill project sustainability and allow for future capacity building. RESULTS: An educational elective was established between the pathology departments of the University of Virginia and Hospital Regional de Occidente in Quetzaltenango, Guatemala. Two residents at a time engaged in a month-long educational elective assisting and learning from the in-country pathologist in anatomic pathology clinical work. CONCLUSIONS: The project is an example of a global health initiative centering on the enhancement of PALM services in a low-resource environment via a bidirectional, sustainable educational exchange.

PD-L1 and Mismatch Repair Status in Uterine Carcinosarcomas.

Uterine carcinosarcomas have few adjuvant treatment options. Programmed cell death ligand-1 (PD-L1) expression in these tumors may predict response to checkpoint inhibitor therapies. An increase in PD-L1 expression has been shown in endometrial carcinomas with mismatch repair (MMR) deficiencies; however, few studies have evaluated PD-L1 expression in uterine carcinosarcomas. We examined PD-L1 expression in 41 cases of uterine carcinosarcoma using combined positive scores (CPS) and tumor proportion scores (TPS), and correlated with MMR status, p53 expression, and epithelial histotype. In addition to confirming the diagnosis of carcinosarcoma, the epithelial components were stratified based on endometrioid versus serous histology. Thirty-three cases (80%) were positive for PD-L1, defined as a CPS score of ≥1 or a TPS score of ≥1%. Twelve cases (29%) showed high expression of PD-L1, defined as a CPS score of ≥10 or a TPS score of ≥10%. The majority of the morphologically adjudicated carcinosarcomas had a serous epithelial component (83%) rather than endometrioid (17%), which was reinforced by aberrant p53 staining predominantly within cases with serous morphology. The majority of carcinosarcomas showed at least focal PD-L1 expression, predominantly in tumor-associated immune cells. Carcinosarcomas with endometrioid morphology were significantly more likely to have high-level PD-L1 (5/7 vs. 7/34; P=0.015). MMR-deficient carcinosarcomas were also more likely to have high-level PD-L1 (2/3 vs. 10/28); however, this did not reach statistical significance (P=0.2) and overall MMR-deficiency was uncommon (3 cases, 7%). These findings suggest that PD-L1 may be additive to MMR testing as a predictive biomarker for checkpoint inhibitor vulnerability in carcinosarcomas.

Putative precancerous lesions of vulvar squamous cell carcinoma.

Precursor lesions of vulvar squamous cell carcinoma (VSCC) can be divided into two major biologic and prognostic groups: HPV-associated and HPV-independent VSCC. These two pathways are categorized as usual vulvar intraepithelial neoplasia (uVIN) with progression to basaloid or warty VSCC and differentiated vulvar intraepithelial neoplasia (dVIN) with progression to the more common keratinizing VSCC. While the HPV-dependent pathway to squamous cell carcinoma is well-understood, the development of squamous cell carcinoma from HPV-independent lesions is less clear. The majority of HPV-independent lesions fall into the dVIN category, and mutations in TP53 have been implicated as the driver behind their development. Other less common HPV-independent precursor lesions, termed differentiated exophytic vulvar intraepithelial lesion (DEVIL) and vulvar acanthosis with altered differentiation (VAAD), have also been characterized as precursors to keratinizing and verrucous VSCC. Inflammatory conditions of the vulva such as lichen sclerosus and lichen simplex chronicus also put patients at risk for developing VSCC. We herein evaluate the available evidence and biologic basis for these VSCC precursor lesions, among other speculated entities, and discuss their clinical, diagnostic, and prognostic features.

Extracellular matrix proteins are time-dependent and regional-specific markers in experimental diffuse brain injury.

INTRODUCTION: The extracellular matrix (ECM) provides structural support for neuronal, glial, and vascular components of the brain, and regulates intercellular signaling required for cellular morphogenesis, differentiation and homeostasis. We hypothesize that the pathophysiology of diffuse brain injury impacts the ECM in a multi-dimensional way across brain regions and over time, which could facilitate damage and repair processes. METHODS: Experimental diffuse TBI was induced in male Sprague-Dawley rats (325-375 g) by midline fluid percussion injury (FPI); uninjured sham rats serve as controls. Tissue from the cortex, thalamus, and hippocampus was collected at 15 min, 1, 2, 6, and 18 hr postinjury as well as 1, 3, 7, and 14 days postinjury. All samples were quantified by Western blot for glycoproteins: fibronectin, laminin, reelin, and tenascin-C. Band intensities were normalized to sham and relative to ß-actin. RESULTS: In the cortex, fibronectin decreased significantly at 15 min, 1 hr, and 2 hr postinjury, while tenascin-C decreased significantly at 7 and 14 days postinjury. In the thalamus, reelin decreased significantly at 2 hr, 3 and 14 days postinjury. In the hippocampus, tenascin-C increased significantly at 15 min and 7 days postinjury. CONCLUSION: Acute changes in the levels of these glycoproteins suggest involvement in circuit dismantling, whereas postacute levels may indicate a restorative or regenerative response associated with recovery from TBI.

Loss of MHC Class I Expression in HPV-associated Cervical and Vulvar Neoplasia: A Potential Mechanism of Resistance to Checkpoint Inhibition.

Tumor cell expression of major histocompatibility complex (MHC) class I is required for antigen presentation and adaptive immune recognition. Absent or diminished MHC class I expression is thought to contribute to immunotherapeutic resistance in some epithelial tumors but has not been previously studied in cervical and vulvar carcinoma. Given that anti-programmed cell death 1 (PD-1) checkpoint inhibition is deployed for programmed cell death ligand 1 (PD-L1)-positive recurrent and metastatic cervical squamous carcinomas, identifying tumors with loss of MHC class I is of clinical interest to optimize the selection of immunotherapeutic candidates. Immunohistochemistry for PD-L1 and MHC class I combined A, B, and C heavy chains (MHC class I) was assessed in 58 human papillomavirus-associated cervical and vulvar lesions, including 27 squamous intraepithelial lesions (SILs) and 31 invasive squamous cell carcinoma (SCC). Although 84% of SCC and 22% of SIL were PD-L1-positive, 35.5% (11/31) of SCC and 18.5% (5/27) of SIL also showed clonal or complete loss of MHC class I. Loss of MHC class I expression was more common in PD-L1-positive (10/26, 38%) versus PD-L1-negative SCC (1/5, 20%). In summary, over one third of human papillomavirus-associated cervical and vulvar SCC show clonal or complete loss of MHC class I expression, including many PD-L1-positive cases. This suggests that the efficacy of checkpoint inhibitors targeting the PD-1/PD-L1 axis may be limited in a subset of cervical and vulvar squamous neoplasms due to an impaired ability to engage with the adaptive immune system related to loss of MHC class I expression.

Optimal age for genetic cancer predisposition testing in hereditary SMARCA4 Ovarian Cancer Families: How young is too young?

Small cell carcinoma of the ovary, hypercalcemic type is a rare, aggressive, and typically fatal ovarian cancer that primarily affects young women less than 40 years of age. It is caused by a pathogenic variant in the SMARCA4 gene, with nearly half of patients found to have germline pathogenic variants and the remainder demonstrating somatic SMARCA4 pathogenic variants. This case report discusses an illustrative case and explores the existing data and potential recommendations to optimize timing of genetic testing in family members, given the presence of a familial germline pathogenic variant.

Synthesis and Characterization of a Leucine-Based Block Co-Polypeptide: The Effect of the Leucine Zipper on Self-Assembly.

The self-assembly behavior of an ABC triblock copolypeptide consisting of poly(ethylene oxide-b-(leucine-s-valine)-b-lysine) (PEO-PLV-PK) was examined via dynamic light scattering in dilute aqueous solution. Leucine is a hydrophobic, α-helix forming polypeptide that exhibits a "zipper effect" in coiled-coil dimers. We hypothesize that the specific interaction afforded by the leucine zipper dominates the thermodynamics of self-assembly through the side-by-side ordering of α-helices, which drives vesicle formation in a polymer with only 6 wt % hydrophobic content. Additionally, a multitude of assembly sizes and morphologies were attainable from a single polymer, depending on the solution processing method. Thermodynamic effects of the leucine zipper can be interpreted, in part, from solubility parameters determined from molecular modeling. The combination of synthesis, solvent processing, and computational studies helps to elucidate the thermodynamic effects of this unique assembly motif on classical self-assembly processes.

Mismatch Repair Deficiency in Uterine Carcinosarcoma: A Multi-institution Retrospective Review.

Immunohistochemistry (IHC) for mismatch repair (MMR) proteins is recommended in endometrial carcinomas as a screening test for Lynch syndrome, and mismatch repair deficiency (MMRd) is reported in ∼30% of cases. However, few studies have evaluated the rate of MMR loss in uterine carcinosarcomas. A 5-year retrospective database search of uterine carcinosarcomas was performed at 3 academic institutions. The histologic diagnoses, type of carcinoma present, and MMR IHC interpretations were confirmed by a gynecologic pathologist. One hundred three cases of uterine carcinosarcomas with available MMR IHC results were identified. Ninety-nine cases (96%) showed intact expression and 4 cases (4%) showed loss of MLH1/PMS2. All MMRd carcinosarcomas identified in this series had an endometrioid carcinomatous component and wild-type p53 expression. In contrast, the majority of MMR intact carcinosarcomas had a serous morphology and aberrant p53 expression. Three additional cases initially diagnosed as carcinosarcoma also revealed MMRd; however, given the lack of clear mesenchymal differentiation, these cases were reclassified as dedifferentiated endometrial carcinomas and were subsequently excluded from the carcinosarcoma category. No cases of Lynch syndrome were identified among carcinosarcoma patients, as all 4 MMRd cases were due to somatic MLH1 hypermethylation. In summary, we found that the rate of MMRd is markedly lower in uterine carcinosarcoma when compared with endometrial carcinoma. In the setting of MMR loss, a diagnosis of dedifferentiated carcinoma should be considered as almost half of the MMRd tumors which were called carcinosarcomas initially were reclassified as dedifferentiated on review. However, given the interobserver variability in the classification of carcinosarcoma versus dedifferentiated carcinoma a universal screening approach that includes uterine carcinosarcoma is still recommended.

Role of Ancillary Techniques in Cervical Biopsy and Endocervical Curettage Specimens as Follow-Up to Papanicolaou Test Results Indicating a Diagnosis of Atypical Squamous Cells, Cannot Exclude High-Grade Squamous Intraepithelial Lesion, or High-Grade Squamous Intraepithelial Lesion.

The Papanicolaou (PAP) test is widely used to screen for cervical cancer. All high-grade lesions such as atypical squamous cells, cannot exclude high-grade squamous intraepithelial lesion (ASC-H), and high-grade squamous intraepithelial lesion, identified on a PAP test should be followed-up by a confirmatory cervical biopsy. In this review, we discuss the challenges in interpreting cervical tissue specimens and the various ancillary techniques used in the evaluation of cervical dysplasia. Ancillary studies include deeper levels, p16 immunohistochemistry (IHC), human papillomavirus (HPV) testing, and, importantly, cyto-histologic correlation. Of these, p16 IHC is consistently sensitive and specific for detecting HSIL. HPV RNA in situ hybridization (ISH) is a newer technique with excellent sensitivity and specificity for detecting virally infected cells and it may be more broadly applicable to both low- and high-grade squamous intraepithelial lesions.

Hierarchical Fractal Assemblies from Poly(ethylene oxide- b-lysine- b-leucine).

Poly(ethylene oxide43- b-lysine62- b-leucine72) (wherein subscripts denote the degree of polymerization) was synthesized via ring-opening polymerization of N-carboxyanhydrides using an amine-terminated poly(ethylene oxide) macroinitiator, with polypeptide blocks produced by sequential monomer addition. Infrared and circular dichroism spectroscopy indicated that the peptide blocks in this polymer formed α-helices in the solid and solution states, respectively. In the aqueous solution, this polymer self-assembled into spherical micelles with a hydrodynamic radius of approximately 90 nm at concentrations between 0.05 and 0.20% w/w and pH values between 2 and 6.5. Upon preparation of transmission electron microscopy (TEM) grids, the micelles at pH 2 underwent hierarchical assembly to produce fractal assemblies, whereas small clusters were observed for micellar solutions at pH 6.5. Cryogenic-TEM of solutions showed spherical micelles, and dynamic light scattering showed no large (∼1 µm) aggregates in the solution, which suggests that fractal formation was a result of the drying process, and that fractals were not present in the solution. This system provides a facile route to nanostructured surfaces, which can be used for applications such as modulating cell adhesion or promoting the growth of neurons.

Thyroid-Like Follicular Carcinoma of the Kidney With Extensive Sarcomatoid Differentiation: A Case Report and Review of the Literature.

Thyroid-like follicular carcinoma of the kidney (TLFCK) is an extremely rare primary renal malignancy that typically has an indolent course and good prognosis. Histologically, this tumor mimics follicular carcinoma of the thyroid; however, typical thyroid markers are negative. There are fewer than 40 cases reported in the literature, and thus, the prognosis and course of disease is not well understood. Sarcomatoid differentiation has never been reported in a case of TLFCK. We present a case of a 48-year-old woman with an aggressive TLFCK with extensive sarcomatoid differentiation and metastatic disease at presentation. We performed targeted next-generation sequencing of both the thyroid-like component and the poorly differentiated sarcomatoid component using our solid tumor panel to evaluate for any disease-associated mutations and to better understand the molecular profile of these tumors.

ROS1 Rearrangement in a Case of Classic Biphasic Pulmonary Blastoma.

Classic biphasic pulmonary blastoma (CBPB) is a rare and aggressive type of non-small cell lung carcinoma (NSCLC) presenting in adults in the fourth to fifth decade. The prognosis is poor and after surgical resection, therapeutic options are often limited. ROS1 is a proto-oncogene receptor tyrosine kinase that has been identified in some types of NSCLC. We report a case of a 36-year-old woman with CBPB, which was subsequently found to have a ROS1 rearrangement. This is the first reported case of a ROS1-rearranged CBPB. This finding has therapeutic implications as these tumors have the potential to be treated with receptor tyrosine kinase inhibitors.