Successful Targeted Therapy of Refractory Pediatric ETV6-NTRK3 Fusion-Positive Secretory Breast Carcinoma

Drug repositioning in thyroid cancer: from point mutations to gene fusions

The diagnosis of thyroid cancer (TC) has increased dramatically in recent years. Papillary TC is the most frequent type and has shown a good prognosis. Conventional treatments for TC are surgery, hormonal therapy, radioactive iodine, chemotherapy, and targeted therapy. However, resistance to treatments is well documented in almost 20% of all cases. Genomic sequencing has provided valuable information to help identify variants that hinder the success of chemotherapy as well as to determine which of those represent potentially druggable targets. There is a plethora of targeted therapies for cancer, most of them directed toward point mutations; however, chromosomal rearrangements that generate fusion genes are becoming relevant in cancer but have been less explored in TC. Therefore, it is relevant to identify new potential inhibitors for genes that are recurrent in the formation of gene fusions. In this review, we focus on describing potentially druggable variants and propose both point variants and fusion genes as targets for drug repositioning in TC.

Nuclear staining for pan-Trk by immunohistochemistry is highly specific for secretory carcinoma of breast: pan-Trk in various subtypes of breast carcinoma

AIMS

Secretory carcinoma of breast (SCB) typically harbours ETV6-NTRK3 gene fusion. Pan-Trk immunohistochemistry analysis (IHC) has been shown to be sensitive for SCB diagnosis. However, weak focal pan-Trk nuclear staining was previously found in 10% of non-secretory breast carcinomas. To further examine pan-Trk IHC specificity, we evaluated pan-Trk staining in various breast carcinoma subtypes.

METHODS

The study cohort consisted of 346 invasive breast carcinomas (IBCs), including 8 SCBs and 48 triple-negative histological mimickers (36 metaplastic carcinomas, including 12 matrix-producing carcinomas; 5 adenoid cystic carcinomas; 5 apocrine carcinomas; 2 acinic cell carcinomas), 101 triple-negative IBCs of no special type, 101 estrogen receptor (ER)-positive/HER2-negative IBCs and 88 HER2-positive IBCs. Six salivary gland secretory carcinomas were also included. Pan-Trk IHC was performed on tumours using a rabbit monoclonal pan-Trk antibody. Any nuclear staining in the invasive carcinoma cells was considered positive.

RESULTS

All 14 secretory carcinomas from breast and salivary gland exhibited moderate to strong pan-Trk nuclear staining. In contrast, no pan-Trk nuclear staining was identified in any of the 338 non-secretory IBCs. Focal cytoplasmic pan-Trk staining was observed in nine non-secretory IBCs (2.7%), and was considered nonspecific and negative.

CONCLUSIONS

Our results indicate that pan-Trk nuclear staining is highly specific for SCB. In low-grade to intermediate-grade IBCs that share histological features with SCB, adding pan-Trk to a routing panel of estrogen receptor/progesterone receptor/HER2 is highly diagnostic. Our results also support using pan-Trk IHC to differentiate SCB from its triple-negative histological mimickers, such as adenoid cystic carcinoma, matrix-producing carcinoma, apocrine carcinoma and acinic cell carcinoma.

Rare subtypes of triple negative breast cancer: Current understanding and future directions

Rare subtypes of triple-negative breast cancers (TNBC) are a heterogenous group of tumors, comprising 5-10% of all TNBCs. Despite accounting for an absolute number of cases in aggregate approaching that of other less common, but well studied solid tumors, rare subtypes of triple-negative disease remain understudied. Low prevalence, diagnostic challenges and overlapping diagnoses have hindered consistent categorization of these breast cancers. Here we review epidemiology, histology and clinical and molecular characteristics of metaplastic, triple-negative lobular, apocrine, adenoid cystic, secretory and high-grade neuroendocrine TNBCs. Medullary pattern invasive ductal carcinoma no special type, which until recently was a considered a distinct subtype, is also discussed. With this background, we review how applying biological principals often applied to study TNBC no special type could improve our understanding of rare TNBCs. These could include the utilization of targeted molecular approaches or disease agnostic tools such as tumor mutational burden or germline mutation-directed treatments. Burgeoning data also suggest that pathologic response to neoadjuvant therapy and circulating tumor DNA have value in understanding rare subtypes of TNBC. Finally, we discuss a framework for advancing disease-specific knowledge in this space. While the conduct of randomized trials in rare TNBC subtypes has been challenging, re-envisioning trial design and technologic tools may offer new opportunities. These include embedding rare TNBC subtypes in umbrella studies of rare tumors, retrospective review of contemporary trials, prospective identification of patients with rare TNBC subtypes entering on clinical trials and querying big data for outcomes of patients with rare breast tumors.

Clinicopathological features and genomic profiles of a group of secretory breast carcinomas in which progressive cases have more complex genomic features

BACKGROUND

Secretory breast carcinoma (SBC) is a rare malignant breast neoplasm with distinct histological features, including solid, microcystic, tubular, and rarely papillary structures, traditionally characterized by a t (12;15) (p13:q25) translocation, which usually leads to ETV6-NTRK3 fusion, suggesting an early event in tumorigenesis. Due to the rarity of this disease, very few genome sequencing studies have been performed on a series of cases, especially progressive cases.

METHODS

Seven lesions from 5 patients diagnosed at the Third Affiliated Hospital of Soochow University from 2007 to 2021 were included. Clinicopathological features and prognosis/survival data were collected. Next-generation DNA sequencing was performed on six of the seven lesions.

RESULTS

In total, 3/7 (42.9%) lesions demonstrated estrogen receptor (ER) expression, including weak, moderate to strong staining, and no lesion demonstrated progesterone receptor (PR) expression. There were no cases of human epidermal growth factor (HER2) overexpression, and the Ki-67 index was low. S-100 and pan-TRK protein were diffusely positively expressed in all cases. All lesions were characterized by a t(12;15) (p13:q25) translocation, leading to ETV6-NTRK3 fusion confirmed by fluorescence in situ hybridization (FISH). The sequencing results showed that ETV6-NTRK3 fusion was the main driver of early tumorigenesis, while SBC with invasive biological behavior had more complex genomic variation in which TERT promoter mutation was detected.

CONCLUSIONS

Immunohistochemical staining of a biomarker panel, including ER, PR, HER2, Ki-67, S-100 and pan-TRK, can be used as an auxiliary diagnostic tool, and FISH detection can be used as a diagnostic tool. ETV6-NTRK3 gene fusion involving multiple sites may drive tumorigenesis, while mutations in the TERT promoter region may be a factor driving tumor progression.

Advancement of secretory breast carcinoma: a narrative review

BACKGROUND AND OBJECTIVE

Secretory breast carcinoma (SBC) is a rare breast malignancy. Most available studies on SBC are case reports or small case series, and the few large-sample studies available lack critical information due to database limitations. To improve the understanding of SBC and provide a reference for clinical practice, we systematically reviewed the demographic, clinical, pathologic, and genetic characteristics of SBC, as well as its treatment and prognosis.

METHODS

We conducted a PubMed search with the keywords "secretory breast carcinoma" or "juvenile breast carcinoma". Relevant English-language publications published from January 1966 to February 2022 were screened manually at 3 levels-title, abstract, and full text-to identify the articles that presented the demographic, clinical, pathologic, and genetic characteristics of SBC, as well as its treatment and prognosis.

KEY CONTENT AND FINDINGS

SBC lacks specific clinical manifestations and has typical pathological and molecular characteristics, including intracellular and extracellular eosinophilic secretions, immune spectrum similar to hormone receptor-positive tumors, and the ETV6-NTRK3 fusion gene. Surgery remains the primary treatment for SBC. Postoperative radiotherapy is recommended by most researchers for adult SBC but not for pediatric patients. The evidence of chemotherapy and endocrine therapy is insufficient, and targeted therapy of the ETV6-NTRK3 fusion gene shows a good response. Most patients with SBC have a good prognosis except for a few patients who experience distant metastases. Future studies will be focused on the molecular characteristics of those patients with SBC who have a poor prognosis.

CONCLUSIONS

The development of histopathology and molecular genetics has promoted the progress of the clinical diagnosis of SBC. The purpose of this review is to serve as a guide for the better clinical treatment of SBC, particularly in the areas of disease identification and prognosis classification for patients.

Elevated ETV6 Expression in Glioma Promotes an Aggressive In Vitro Phenotype Associated with Shorter Patient Survival

Background: GBM astrocytes may adopt fetal astrocyte transcriptomic signatures involved in brain development and migration programs to facilitate diffuse tumor infiltration. Our previous data show that ETS variant 6 (ETV6) is highly expressed in human GBM and fetal astrocytes compared to normal mature astrocytes. We hypothesized that ETV6 played a role in GBM tumor progression. Methods: Expression of ETV6 was first examined in two American and three Chinese tissue microarrays. The correlation between ETV6 staining intensity and patient survival was calculated, followed by validation using public databases—TCGA and REMBRANDT. The effect of ETV6 knockdown on glioma cell proliferation (EdU), viability (AnnexinV labeling), clonogenic growth (colony formation), and migration/invasion (transwell assays) in GBM cells was tested. RNA sequencing and Western blot were performed to elucidate the underlying molecular mechanisms. Results: ETV6 was highly expressed in GBM and associated with an unfavorable prognosis. ETV6 silencing in glioma cells led to increased apoptosis or decreased proliferation, clonogenicity, migration, and invasion. RNA-Seq-based gene expression and pathway analyses revealed that ETV6 knockdown in U251 cells led to the upregulation of genes involved in extracellular matrix organization, NF-κB signaling, TNF-mediated signaling, and the downregulation of genes in the regulation of cell motility, cell proliferation, PI3K-AKT signaling, and the Ras pathway. The downregulation of the PI3K-AKT and Ras-MAPK pathways were further validated by immunoblotting. Conclusion: Our findings suggested that ETV6 was highly expressed in GBM and its high expression correlated with poor survival. ETV6 silencing decreased an aggressive in vitro phenotype probably via the PI3K-AKT and Ras-MAPK pathways. The study encourages further investigation of ETV6 as a potential therapeutic target of GBM.

The Molecular Predictive and Prognostic Biomarkers in Metastatic Breast Cancer: The Contribution of Molecular Profiling

The past decade was marked by several important studies deciphering the molecular landscape of metastatic breast cancer. Although the initial goal of these studies was to find driver oncogenic events to explain cancer progression and metastatic spreading, they have also permitted the identification of several molecular alterations associated with treatment response or resistance. Herein, we review validated (PI3KCA, ESR1, MSI, NTRK translocation) and emergent molecular biomarkers (ERBB2, AKT, PTEN, HRR gene, CD274 amplification RB1, NF1, mutational process) in metastatic breast cancer, on the bases of the largest molecular profiling studies. These biomarkers will be classed according the level of evidence and, if possible, the ESCAT (ESMO) classification. Finally, we will provide some perspective on development in clinical practice for the main biomarkers.

Narrative review of progress in pathological diagnosis of breast cancer

Background and Objective

Breast cancer (BC) contains a spectrum of diseases with distinctive presentations, morphology, biology, and clinical phenotypes. BC varies significantly in its biological behaviour and response to treatment. Combination of the traditional histopathological with the molecular types of BC allows more accurate prediction of its biological and clinical heterogeneity. We aim to provide a review of the latest advances in breast pathological detection and related biomarkers.

Methods

We reviewed English publications in PubMed related to progress in pathological diagnosis of breast cancer from 2000 to 2022.

Key Content and Findings

This review outlines the latest advances in breast pathological detection and related biomarkers, include histological types, human epidermal growth factor receptor 2 (HER2), estrogen receptor (ER), Ki67, tumor infiltrating lymphocytes. The histological types and molecular pathological markers of BC are closely related to its treatment and prognosis. The 5th edition World Health Organization (WHO) classification of Breast tumours more emphasis on the clinical significance of histological types. The consensus on the testing of biomarkers for BC has also become more precise, not only suggesting that the primary and metastases of BC be detected for the expressions of ER, PR, and HER2, but also introducing the concept of ER and HER2 low-expressions. In addition, the Ki67 proliferation index plays an important role in the expected therapeutic effect. With the gradual rise of immunotherapy, treatments based on programmed death protein-1/programmed death protein-ligand 1 (PD-1/PD-L1) immune checkpoint inhibitors have achieved some results in clinical efficacy for BC, while studies related to tumor infiltrating lymphocytes (TILs) are gradually gaining more attention.

Conclusions

With the deep and continued research of BC, these discoveries will demonstrate significant clinical application value in the future.

Diagnosis and management of TRK fusion cancer

The tropomyosin receptor kinase (TRK) family of proteins is encoded by neurotrophic tyrosine receptor kinase (NTRK) genes and has a role in the development and normal functioning of the nervous system. NTRK gene fusions have been identified as oncogenic drivers in a wide range of tumors in both adult and pediatric patients. There has recently been a paradigm shift in cancer treatment toward biomarker-based targeted therapies, as an increasing number of actionable targets are being identified across different tumors and/or tumor histologies. These targeted agents offer greater comparative effectiveness and safety vs historical nontargeted standard therapies. The development of drugs that specifically target oncogenic drivers of cancer has led to the emergence of screening technologies to identify the patients most likely to benefit from targeted therapy. This review describes the role of NTRK gene fusions in cancer and outlines the epidemiology of NTRK gene fusions, the therapeutic benefits of targeting TRK fusions with small molecule inhibitors, and recommendations for NTRK gene fusion testing in adult and pediatric patients with cancer, in order to guide treatment decisions.

Triple-Negative Breast Cancer Histological Subtypes with a Favourable Prognosis

Simple Summary

Breast cancers that lack expression of the predictive markers oestrogen receptor, progesterone receptor and human epidermal growth factor receptor-2 are known as triple-negative breast cancers (TNBCs) and are generally considered to have a poor prognosis. As available targeted treatments are not effective, aggressive chemotherapy is frequently advocated for patients with TNBC. It is now becoming apparent that TNBC is not one entity but constitutes a range of malignancies with different clinical behaviour. This paper reviews 7 distinct histological subtypes of TNBC where the overall prognosis is favourable, and aggressive systemic treatment is generally not indicated. Their recognition and separation from the larger group of no special type TNBC are important. The members of the European Working Group for Breast Screening Pathology review the morphology, known molecular features and reported outcomes, and formulate a consensus statement regarding the approach to the subtypes that are associated with a favourable prognosis.

Abstract

Triple-negative breast cancers (TNBC), as a group of tumours, have a worse prognosis than stage-matched non-TNBC and lack the benefits of routinely available targeted therapy. However, TNBC is a heterogeneous group of neoplasms, which includes some special type carcinomas with a relatively indolent course. This review on behalf of the European Working Group for Breast Screening Pathology reviews the literature on the special histological types of BC that are reported to have a triple negative phenotype and indolent behaviour. These include adenoid cystic carcinoma of classical type, low-grade adenosquamous carcinoma, fibromatosis-like metaplastic carcinoma, low-grade mucoepidermoid carcinoma, secretory carcinoma, acinic cell carcinoma, and tall cell carcinoma with reversed polarity. The pathological and known molecular features as well as clinical data including treatment and prognosis of these special TNBC subtypes are summarised and it is concluded that many patients with these rare TNBC pure subtypes are unlikely to benefit from systemic chemotherapy. A consensus statement of the working group relating to the multidisciplinary approach and treatment of these rare tumour types concludes the review.

Triple-negative breast cancer and basal-like subtype : Pathology and targeted therapy

Triple-negative breast cancer (TNBC) is a heterogenous disease. For personalized medicine, it is essential to identify and classify tumor subtypes to develop effective therapeutic strategies. Although gene expression profiling has identified several TNBC subtypes, classification of these tumors remains complex. Most TNBCs exhibit an aggressive phenotype, but some rare types have a favorable clinical course. In this review, we summarize the classification and characteristics related to the various TNBC subtypes, including the rare types. Therapeutic methods that are suitable for each subtype are also discussed. Of the intrinsic breast cancer subtypes identified by gene expression analysis, the basal-like subtype specifically displayed decreased expression of an estrogen receptor (ER) and human epidermal growth factor receptor 2 (HER2) cluster. We also present results that characterize the TNBC and basal-like phenotypes. TNBC may be categorized into four major classes : basal-like, immune-enriched, mesenchymal, and luminal androgen receptor. Therapeutic strategies for each subtype have been proposed along with newly approved targeted therapies for TNBC, such as immune checkpoint inhibitors. Understanding the classification of TNBC based on gene expression profiling in association with clinicopathological factors will facilitate accurate pathological diagnosis and effective treatment selection. J. Med. Invest. 68 : 213-219, August, 2021.

Secretory breast carcinoma in a female adult with liver metastsis: a case report and literature review

BACKGROUND

Secretory breast carcinoma is an uncommon subset of breast cancer that usually has a favorable outcome. Although initially described in children, it also occurs in adults where it may metastasize, possibly resulting in death. To date, only 20 cases of secretory breast carcinoma with distant metastases have been described.

CASE PRESENTATION

A 42-year-old female presented with liver metastasis after modified radical mastectomy of the left breast in 2008 at 34 years of age. The liver metastasis was morphologically similar to the primary tumor. Pan-TRK and Fluorescence in situ hybridization showed a rearrangement in the ETV6 gene. She subsequently underwent adjuvant chemotherapy with a fatal outcome.

CONCLUSIONS

Although secretory breast carcinoma is usually associated with favorable outcomes, our study and reviews provide a novel insight into the genetic spectrum and treatment of secretory breast carcinoma showing reduced expression of hormone receptors, abnormal genomic profiles, and possible poor prognosis. Targeted therapy may curb clinically aggressive cases. Additional molecular investigations are needed to determine the links between specific mutations and poor prognosis.

Molecular Pathology of Breast Tumors: Diagnostic and Actionable Genetic Alterations

Breast cancer is a heterogenous disease with various histologic subtypes, molecular profiles, behaviors, and response to therapy. After the histologic assessment and diagnosis of an invasive breast carcinoma, the use of biomarkers, multigene expression assays and mutation profiling may be used. With improved molecular assays, the identification of somatic genetic alterations in key oncogenes and tumor suppressor genes are playing an increasingly important role in many areas of breast cancer care. This review summarizes the most clinically significant somatic alterations in breast tumors and how this information is used to facilitate diagnosis, provide potential treatment options, and identify mechanisms of resistance.

Secretory carcinoma of the breast with multiple distant metastases in the brain and unfavorable prognosis: a case report and literature review

Background

Secretory carcinoma of the breast is one of the rarest entities, accounting for less than 0.15 % of all infiltrating breast carcinomas. It has characteristic histopathological and molecular features and, in general, a more favorable prognosis. In this case report, we describe a local, advanced secretory carcinoma of the breast with aggressive course and an unfavorable outcome.

Case presentation

A hard, painless, and palpably bossed mass approximately 12.0 cm in diameter occupied most of the left breast of a 39-year-old woman with fixation to the overlying skin. Breast ultrasonography and magnetic resonance imaging (MRI) scans gave the same grading as BI-RADS IV. A needle biopsy was performed, and the pathological diagnosis was secretory carcinoma. Neoadjuvant chemotherapy (NAC) was then performed, after which ultrasonography and MRI scans revealed chemo-resistance of the tumor to NAC. Left breast mastectomy and axillary lymphadenectomy were subsequently performed. Tumor cells were triple-negative and positive for S-100 and periodic acid-Schiff (PAS) staining. Fluorescence in-situ hybridization (FISH) analysis indicated a fusion arrangement of the ETV6-NTRK3 gene. The patient developed multiple distant metastases in the brain and died of these metastases 19 months after initial diagnosis.

Conclusions

Secretory carcinomas of the breast have been described as a low-grade histologic subtype with a favorable prognosis. This case showed chemo-resistance to neoadjuvant chemotherapy, multiple distant metastases, and a final unfavorable outcome. Further research is needed to better understand the behavior and treatment of this rare tumor.

NTRK Fusions, from the Diagnostic Algorithm to Innovative Treatment in the Era of Precision Medicine

In the era of precision medicine, the identification of several predictive biomarkers and the development of innovative therapies have dramatically increased the request of tests to identify specific targets on cytological or histological samples, revolutionizing the management of the tumoral biomaterials. The Food and Drug Administration (FDA) has recently approved a selective neurotrophic tyrosine receptor kinase (NTRK) inhibitor, larotrectinib. Contemporarily, the development of multi-kinase inhibitors with activity in tumors carrying TRK fusions is ongoing. Chromosomal translocations involving the NTRK1, NTRK2, and NTRK3 genes result in constitutive activation and aberrant expression of TRK kinases in numerous cancer types. In this context, the identification of tumors harboring TRK fusions is crucial. Several methods of detection are currently available. We revise the advantages and disadvantages of different techniques used for identifying TRK alterations, including immunohistochemistry, fluorescence in situ hybridization, reverse transcriptase polymerase chain reaction, and next generation sequencing-based approaches. Finally, we propose a diagnostic algorithm based on histology and the relative frequency of TRK fusions in each specific tumor, considering also the economic feasibility in the clinical practice.

[Multicentric secretory carcinoma of the breast: Case report and review of the literature]

Secretory carcinoma of the breast is a rare entity, characterized by the presence of intra- and extracellular, eosinophilic and acelular secretions. They are negative for hormone receptors and do not express human epidermal growth factor receptor HER-2/neu. However, the clinical outcome is favorable. Multicentricity is very unusual. We report a case of a 32-year-old woman with a multicentric secretory carcinoma of the breast. The main pathological features are discussed together with a review of the pertinent literature.

Roles of TrkC Signaling in the Regulation of Tumorigenicity and Metastasis of Cancer

Tropomyosin receptor kinase (Trk) C contributes to the clinicopathology of a variety of human cancers, and new chimeric oncoproteins containing the tyrosine kinase domain of TrkC occur after fusion to the partner genes. Overexpression of TrkC and TrkC fusion proteins was observed in patients with a variety of cancers, including mesenchymal, hematopoietic, and those of epithelial cell lineage. Both microRNAs (miRNAs) and long non-coding RNAs (lncRNAs) were involved in the regulation of TrkC expression through transcriptional and posttranscriptional alteration. Aberrant activation of TrkC and TrkC fusion proteins markedly induces the epithelial-mesenchymal transition (EMT) program, growth rate, tumorigenic capacity via constitutive activation of Ras-MAP kinase (MAPK), PI3K-AKT, and the JAK2-STAT3 pathway. The clinical trial of TrkC or TrkC fusion-positive cancers with newly developed Trk inhibitors demonstrated that Trk inhibitors were highly effective in inducing tumor regression in patients who do not harbor mutations in the kinase domain. Recently, there has been a progressive accumulation of mutations in TrkC or the TrkC fusion protein detected in the clinic and its related cancer cell lines caused by high-throughput DNA sequencing. Despite given the high overall response rate against Trk or Trk fusion proteins-positive solid tumors, acquired drug resistance was observed in patients with various cancers caused by mutations in the Trk kinase domain. To overcome acquired resistance caused by kinase domain mutation, next-generation Trk inhibitors have been developed, and these inhibitors are currently under investigation in clinical trials.

[Secretory carcinoma of the salivary gland (mammary analogue secretory carcinoma) in children]

Secretory carcinoma of the salivary gland is a tumor that was first described less than 10 years ago and that mainly occurs in the parotid salivary gland in the elderly. Analyzing the literature over 8 years since the first description of the tumor identifies the main clinical, morphological, and genetic signs of the diagnosis of secretory carcinoma with a focus on the pediatric population. Four new cases of secretory carcinoma of the salivary glands, which have been diagnosed in children of the youngest age encountered in the literature, are also described.

Clinicopathologic and molecular features of intracranial desmoplastic small round cell tumors

Desmoplastic small round cell tumors (DSRCTs) are highly aggressive sarcomas that most commonly occur intra-abdominally, and are defined by EWSR1-WT1 gene fusion. Intracranial DSRCTs are exceptionally rare with only seven previously reported fusion-positive cases. Herein, we evaluate the clinical, morphologic, immunohistochemical and molecular features of five additional examples. All patients were male (age range 6-25 years; median 11 years), with four tumors located supratentorially and one within the posterior fossa. The histologic features were highly variable including small cell, embryonal, clear cell, rhabdoid, anaplastic and glioma-like appearances. A prominent desmoplastic stroma was seen in only two cases. The mitotic index ranged from <1 to 12/10 HPF (median 5). While all tumors showed strong desmin positivity, epithelial markers such as EMA, CAM 5.2 and other keratins were strongly positive in only one, focally positive in two and negative in two cases. EWSR1-WT1 gene fusion was present in all cases, with accompanying mutations in the TERT promoter or STAG2 gene in individual cases. Given the significant histologic diversity, in the absence of genetic evaluation these cases could easily be misinterpreted as other entities. Desmin immunostaining is a useful initial screening method for consideration of a DSRCT diagnosis, prompting confirmatory molecular testing. Demonstrating the presence of an EWSR1-WT1 fusion provides a definitive diagnosis of DSRCT. Genome-wide methylation profiles of intracranial DSRCTs matched those of extracranial DSRCTs. Thus, despite the occasionally unusual histologic features and immunoprofile, intracranial DSRCTs likely represent a similar, if not the same, entity as their soft tissue counterpart based on the shared fusion and methylation profiles.

Rare epithelial breast cancer: surgery and adjuvant therapy

Breast cancer is a heterogenous disease, exhibiting a wide range of morphological phenotypes shaping its prognosis and clinical course. However, optimal management of rarer breast cancer subtypes is often undefined and controversial in literature due to the lack of large studies and randomised trials. This review aims to discuss the treatment of 13 rare epithelial subtypes, focussing on surgery and adjuvant therapies.

New designs in early clinical drug development

The availability of an unprecedented massive amount of data has provided a magnificent window of opportunity for the development of new drugs. There are currently more drugs in development targeting cancer than any other disease. While this has brought us new waves of drugs, the counterpart is that with these new molecules we have different mechanisms of action, drug kinetics and dynamics, response types and toxicity profiles, which impair classical early clinical trial designs from being effective and efficient. What we once treated as a 'one-size-fits-all' homogeneous disease, has now been uncovered to be a rather heterogeneous condition with multiple targetable mutations. As this generates endless scenarios, it will be impossible to design single 'me-too' trials for every different disease, target, biomarker and agent. To overcome this, we must focus on improving early phase studies, undoubtedly the most critical step from bench to bedside. Goals include decreasing clinical development times, lowering research and development costs and optimizing decisions in advancing through the several phases with a higher degree of certainty in exchange for less failed attempts. We need more informative and, really, transformative early phase designs that seek to obtain the typical late phase objectives in a time continuum and to allow for more robust and efficient go/no-go decisions. With this in mind, different classes of drugs seem to fit with different designs, which present solutions to the different challenges that they pose after finding the maximum tolerated dose/optimum biological dose. This article reviews these concepts and designs and how they can adapt to this new reality in early phase investigation.

Pure secretory carcinoma in situ: a case report and literature review

Background

Secretory breast carcinoma is an exceptionally rare type of breast carcinoma. Only 5 cases of pure secretory carcinoma in situ have been reported in English literature. Herein, we reported a rare case of pure secretory breast carcinoma in situ.

Case presentation

The patient is a 38-year-old female with bloody discharge from the left nipple. Microscopically, the terminal-duct lobular units were enlarged and filled with tumor cells. The tumor cells were arranged in cystic, microcystic, solid and papillary pattern and formed a honeycomb-like appearance. The presence of intracellular and extracellular eosinphilic PAS-positive material was the most remarkable feature. Immunohistochemically, myoepithelial markers highlighted the complete presence of myoepithelial cells around the tumour nests. Tumour cells were strongly positive for S-100 and CK5/6, negative for ER, PR and HER2. Fluorescence in situ hybridization analysis showed ETV6-NTRK3 fusion.

Conclusion

Secretory carcinoma in situ shares the same morphological, immunohistochemical and molecular features with invasive secretory carcinoma except that the papillary growth pattern is more common in the introductal components. Cautions should be taken to distinguish secretory carcinoma in situ from other introductal lesions. Our report is an important supplement to the morphology spectrum of secretory breast carcinoma.

Secretory carcinoma of the breast: clinicopathologic profile of 14 cases emphasising distant metastatic potential

AIMS

Secretory carcinoma of the breast (SCB) is a rare histological type of breast carcinoma with a generally indolent clinical behaviour. We aim to elucidate the clinical, pathological and molecular findings of SCB cases and identify characteristics associated with aggressive clinical courses.

METHODS AND RESULTS

Fourteen patients with SCB were identified, including 12 women and two men, with a median age of 56 years (range = 8-81 years). Clinical data, histological diagnosis, molecular findings and follow-up were reviewed. Eight patients presented with palpable masses and four patients with radiographic abnormalities. All cases were unilateral. Surgical procedures included excisional biopsies and ipsilateral mastectomies. In 10 cases, oestrogen receptor (ER), progesterone receptor (PR) and human epidermal growth factor receptor 2 (HER2) results were obtained, with six cases positive for ER and three positive for PR. All cases lacked HER2 overexpression. Sentinel lymph node biopsy was performed in 10 cases, and two patients had axillary lymph node metastasis. Follow-up ranged from 21 to 212 months (median = 70 months). Two patients developed distant metastasis of SCB. Molecular analysis of these aggressive tumours revealed amplification of the 16p13.3 locus, a TERT promotor mutation and loss of 9p21.3 locus. Review of the literature for SCB cases with distant metastasis was performed.

CONCLUSIONS

Although SCBs are generally associated with a favourable prognosis, our study and review demonstrate that a subset of SCBs may develop distant metastases. Further studies are warranted to identify markers predictive of more aggressive clinical behaviour in this rare breast cancer subtype.

TRK Fusion Cancers in Children: A Clinical Review and Recommendations for Screening

Chromosomal translocations involving the NTRK1, NTRK2, and NTRK3 genes (TRK fusions), which encode the neurotrophin tyrosine kinase receptors TRKA, TRKB, and TRKC, can result in constitutive activation and aberrant expression of TRK kinase. Certain cancers almost universally harbor TRK fusions, including infantile fibrosarcoma, cellular congenital mesoblastic nephroma, secretory breast cancer, and mammary analog secretory carcinoma of the salivary gland. TRK fusions have also been identified at lower frequencies across a broad range of other pediatric cancers, including undifferentiated sarcomas, gliomas, papillary thyroid cancers, spitzoid neoplasms, inflammatory myofibroblastic tumors, and acute leukemias. Here we review the prevalence and diseases associated with TRK fusions and methods of detection of these fusions in light of the recent development of selective TRK inhibitors, such as larotrectinib, which demonstrated a 75% response rate across children and adults with TRK fusion cancers. We provide recommendations for screening pediatric tumors for the presence of TRK fusions, including the use of immunohistochemistry or fluorescence in situ hybridization for patients with tumors likely to harbor TRK fusions. Further, we recommend next-generation sequencing for tumors that have a relatively low prevalence of TRK fusions, both to identify patients who may benefit from TRK inhibition and to identify other targetable oncogenic drivers that exist in the same tumor types.

Recurrent EML4-NTRK3 fusions in infantile fibrosarcoma and congenital mesoblastic nephroma suggest a revised testing strategy

Infantile fibrosarcoma and congenital mesoblastic nephroma are tumors of infancy traditionally associated with the ETV6-NTRK3 gene fusion. However, a number of case reports have identified variant fusions in these tumors. In order to assess the frequency of variant NTRK3 fusions, and in particular whether the recently identified EML4-NTRK3 fusion is recurrent, 63 archival cases of infantile fibrosarcoma, congenital mesoblastic nephroma, mammary analog secretory carcinoma and secretory breast carcinoma (tumor types that are known to carry recurrent ETV6-NTRK3 fusions) were tested with NTRK3 break-apart FISH, EML4-NTRK3 dual fusion FISH, and targeted RNA sequencing. The EML4-NTRK3 fusion was identified in two cases of infantile fibrosarcoma (one of which was previously described), and in one case of congenital mesoblastic nephroma, demonstrating that the EML4-NTRK3 fusion is a recurrent genetic event in these related tumors. The growing spectrum of gene fusions associated with infantile fibrosarcoma and congenital mesoblastic nephroma along with the recent availability of targeted therapies directed toward inhibition of NTRK signaling argue for alternate testing strategies beyond ETV6 break-apart FISH. The use of either NTRK3 FISH or next-generation sequencing will expand the number of cases in which an oncogenic fusion is identified and facilitate optimal diagnosis and treatment for patients.

Larotrectinib (LOXO-101)

One of the most challenging issues in oncology research and treatment is identifying oncogenic drivers within an individual patient's tumor which can be directly targeted by a clinically available therapeutic drug. In this context, gene fusions as one important example of genetic aberrations leading to carcinogenesis follow the widely accepted concept that cell growth and proliferation are driven by the accomplished fusion (usually involving former proto-oncogenes) and may therefore be successfully inhibited by substances directed against the fusion. This concept has already been established with oncogenic gene fusions like BCR-ABL in chronic myelogenous leukemia (CML) or anaplastic lymphoma kinase (ALK) in lung cancer, including special tyrosine kinase inhibitors (TKIs) which are able to block the activation of the depending downstream proliferation pathways and, consequently, tumor growth. During the last decade, the NTRK1, 2, and 3 genes, encoding the TRKA, B, and C proteins, have attracted increasing attention as another significant and targetable gene fusion in a variety of cancers. Several TRK inhibitors have been developed, and one of them, Larotrectinib (formerly known as LOXO-101), represents an orally available, selective inhibitor of the TRK receptor family that has already shown substantial clinical benefit in both pediatric and adult patients harboring an NTRK gene fusion over the last few years.