Fumarate Hydratase-Deficient Leiomyoma of the Uterine Corpus: Comparative Morphologic Analysis of Protein-Deficient Tumors With and Without Pathogenic Germline Fumarate Hydratase Gene Mutations.

Deficiency of fumarate hydratase (FH) protein expression in uterine corpus leiomyomas may be attributable to either germline or somatic mutations of the FH gene, the former being definitional for the hereditary leiomyomatosis and renal cell cancer syndrome. The authors assess whether, using previously reported FH-associated morphologic features, FH protein-deficient uterine corpus leiomyomas associated with a pathogenic germline mutations of the FH gene (group 1) are distinguishable from FH protein-deficient uterine corpus leiomyomas without such mutations (and whose FH protein loss is presumed to be attributable to somatic/epigenetic inactivation or other unknown phenomena: group 2). Groups 1 and 2 were compared regarding a variety of clinicopathologic features, including 7 core "FH-associated" tumoral morphologic features: staghorn vasculature; alveolar-type edema; bizarre nuclei; chain-like tumor nuclei; hyaline cytoplasmic globules; prominent nucleoli, intranuclear inclusions, and perinucleolar halos; and prominent eosinophilic/fibrillary cytoplasm. Among 2418 patients diagnosed with uterine corpus leiomyoma during the study period, FH-associated morphologic features were reported in 1.5% (37 patients), and FH immunohistochemistry was performed in 29 (1.19%). Fourteen (48.27%) of the 29 patients showed FH protein deficiency by immunohistochemistry. Twelve patients underwent germline testing, of which 8 (66.7%) were classified as group 1 and 4 (33.3%) as group 2. FH protein-deficient tumors were larger (10.44 vs 4.08 cm, P = 0.01) and associated with younger patients (42.05 vs 47.97, P = 0.004) than 370 randomly selected uterine leiomyoma controls. Groups 1 and 2 showed no significant differences in patient age and tumor size. In group 1 tumors, the FH-associated morphologic features were generally present diffusely; all group 1 tumors displayed ≥5 FH-associated features, whereas all group 2 tumors displayed <5 FH-associated features (means 6.5 ± 0.53 vs 3.5 ± 1.00, P < 0.001). Notably, eosinophilic/fibrillary cytoplasm and alveolar-type edema were each significantly more prevalent in group 1 tumors than group 2 tumors (P = 0.018 for both). No single morphologic feature was found to be completely sensitive and specific in making the distinction between group 1 and 2 tumors. Our findings suggest that groups 1 and 2 are unlikely to be morphologically distinguishable by individual morphologic features. Whether there is a combination of features that can reliably make this distinction is unclear and will require additional studies with larger cohorts.

HER2 Status Assessment in Endometrial Serous Carcinoma: Comparative Analysis of Two Proposed Testing and Interpretation Algorithms.

HER2 status is now routinely assessed in endometrial serous carcinoma (ESC) due to the reported predictive value of HER2 protein overexpression and/or gene amplification. Herein the authors compare 2 proposed testing and interpretation guidelines for HER2 in ESC. Forty-three consecutive cases of ESC that had been dually tested by both HER2 immunohistochemistry (IHC) and fluorescence in situ hybridization (FISH) were interpreted using 2 sets of guidelines. Guideline set 1 (GS1) is the 2018 American Society of Clinical Oncology/College of American Pathologists guidelines for breast cancer. Guideline set 2 (GS2) is a recent proposal that is a slight modification of the enrollment criteria for the clinical trial (NCT01367002) that demonstrated a survival benefit for anti-HER2 therapy in ESC. By IHC, GS1 and GS2, respectively classified 39.5% (17/43) and 28% (12/43) of ESC as HER2-negative, 37.2% (16/43) and 53.4% (23/43) as HER2 equivocal, and 23.2% (10/43) and 18.6% (8/43) as HER2-positive ( P > 0.05 for all). IHC and FISH were highly concordant at the extremes using either set of guidelines, as no cases were found to be IHC3+/FISH-negative or IHC 0-1+/FISH-positive. GS1 and GS2 were comparable regarding the proportion of IHC equivocal cases that were HER2 amplified by FISH (19% vs 23% respectively; [ P = 0.71]). GS1 and GS2 displayed 98% (42/43) concordance regarding the final (IHC and/or FISH-based) classification of tumors as being HER2-positive or negative, and the same 13 cases were ultimately classified as HER2 amplified using either GS1 or GS2. One "discordant" case was classified as HER2-positive using GS2 but HER2-negative using GS1 (HER2 IHC score 2+ using both guidelines, HER2:CEP17 signal ratio of 3, HER2 signal number of 3.4). Six (14%) of the 43 cases (FISH Groups: 2, 3, and 4) would require IHC results to interpret the FISH findings using GS1. Because GS1 requires that the HER2 IHC staining be observed within a homogeneous and contiguous invasive cell population, and this is not a requirement in GS2, GS2 may be better suited for ESC given its frequently heterogeneous staining pattern. Additional studies may be required on the optimal interpretation of problematic dual-probe FISH scenarios in GS2 and the necessity for IHC correlation in such scenarios. Using either set of guidelines, our findings support a reflex testing strategy of restricting FISH testing to cases that are IHC equivocal.

GATA3 Expression in HPV-associated and HPV-independent Vulvar Squamous Cell Carcinomas: Patterns of Expression and Prognostic Significance.

Substantial diminution or loss of GATA3 expression is reportedly frequent in human papillomavirus-independent (HPVI), p53-mediated vulvar intraepithelial neoplasia. Herein, we study GATA3 expression in vulvar squamous cell carcinoma (VSCC) and assess its clinicopathologic significance. Eighty-six cases of VSCC diagnosed at a single institution were immunohistochemically assessed for their expression of GATA3, as well as any possible relationships with patient outcomes and other clinicopathologic parameters. Given that GATA3 expression pattern in the normal vulvar epidermis is typically strong basal staining with a uniform upward extension until at least the mid epidermal layers, VSCCs were scored using a previously reported tripattern system: pattern 0 (>75% tumor staining), pattern 1 (25% to 75% staining), and pattern 2 (<25% staining). Severe loss of GATA3 expression (pattern 2) was present in both human papillomavirus-associated (HPVA) and HPVI VSCC but was significantly more common in HPVI cases ( P <0.001). Among 52 HPVA VSCCs, 16 (30.7%), 15 (28.8%), and 21 (40.3%) cases showed patterns 0, 1, 2 staining whereas among 34 HPVI VSCCs, the respective frequencies were 1 (2.9%), 5 (14.7%), and 28 (82.3%). None of the 30 p53 abnormal VSCCs showed pattern 0 staining (0%). Five (16.6%) and 25 (83.3%) showed patterns 1 and 2 staining, respectively. On univariate analysis, the pattern 2 cohort showed a significantly worse overall survival (OS) and disease-free survival (DFS) than the pattern 0 or 1 cohort ( P =0.011 and 0.024, respectively), but this finding was not independent of stage on multivariate analysis ( P =0.34; hazard ratio: 1.82; 95% CI: 0.55-6.06). Subgroup analysis of the p53 wild-type cases showed significantly worse OS for pattern 2 than the pattern 0 or 1 cohorts, independent of stage ( P =0.04; hazard ratio: 6.5; 95% CI: 1.08-39.8). Subgroup analysis of p53 abnormal cases, however, showed no difference in OS and DFS among the 3-tiered GATA3 cohorts. In summary, loss of GATA3 may be seen in both HPVA and HPVI VSCCs but is significantly more common in HPVI SCCs. Loss or substantial diminution of GATA3 expression (pattern 2) is a negative prognostic factor in vulvar SCCs, but only in the p53 wild-type subset, where its negative prognostic significance appears to be independent of stage.

GATA3 immunohistochemistry as a diagnostic adjunct for differentiated vulvar intraepithelial neoplasia: utility and limitations.

Herein, the authors evaluate the diagnostic utility and limitations of GATA3 immunohistochemistry for the distinction of differentiated vulvar intraepithelial neoplasia (dVIN) from its potential mimics. Immunohistochemical studies for GATA3, p53, and p16 were performed on 124 pathologic vulvar tissues, inclusive of dVIN (n = 21), vulvar aberrant maturation (n = 10), high-grade squamous intraepithelial lesion (HSIL) (n = 44), and 49 non-neoplastic vulvar dermatoses of various types. GATA3 expression was scored using a modification of previously proposed criteria: pattern 0 (no significant loss of basal layer staining, >75% staining), pattern 1 (25-75% staining), and pattern 2 (<25% staining). With the exception of lichen sclerosus, 8% of which showed pattern 1 or 2 staining, all other non-neoplastic lesions showed pattern 0 expression. Aberrant GATA3 expression (i.e., patterns 1 or 2) was present in 90% of dVIN cases (2 [9.5%], 3 [14.3%], 16 [76.2%] with patterns 0, 1, and 2 respectively), 90% of vulvar aberrant maturation cases (1 [10%],7 [70%], 2 [20%] with patterns 0, 1, and 2 respectively), and 15.9% of HSIL cases (84.1% pattern 0; 2.3% pattern 1; 13.6% pattern 2). All HSIL cases were p16 positive, including the 7 pattern 1 and 2 cases. All cases of dVIN-like HSIL were pattern 0, and all (n = 2) cases of HSIL-like (basaloid) dVIN were pattern 2 (both of the latter cases displayed complete absence of epidermal staining). Only 1 dVIN case was both pattern 0 and p53-wild-type. We conclude that GATA3 is useful for the distinction of dVIN from non-neoplastic dermatoses and from HSIL, but is best used as part of a panel that includes p53 and p16 to mitigate its limitations.

Tumor budding activity is an independent prognostic factor in squamous cell carcinoma of the vulva.

Tumor budding activity (TBA) is recognized as a potential prognostic factor in carcinomas from several anatomic sites. This study evaluates the prognostic value of TBA in a cohort of squamous cell carcinoma of the vulva (VSCC). TBA, defined as clusters of <5 tumor cells that are detached from the main tumor and that infiltrate into surrounding stroma, was assessed in 82 cases of surgically excised VSCC and correlated with patient outcomes. All cases were classified into one of 3 groups: no TBA, low TBA (1-14 foci), and high TBA (≥15 foci). Twenty-three (29.1%), 37 (45.1%), and 22 (26.8%) cases showed no, low, and high TBA, respectively. High TBA was associated with reduced overall survival (OS) on multivariate analysis independent of FIGO stage, human papillomavirus (HPV) status, and p53 status. The majority of tumors with high TBA displayed a p53 mutant staining pattern (77.3%, 17 of 22). The 17 patients whose tumors displayed a p53 mutant/high TBA profile had worse outcomes when compared with 15 patients whose tumors showed a p53 mutant/no TBA or p53 mutant/low TBA profile (mean OS 37.5 versus 63.3 months, respectively, P = .002). High TBA was observed in only 5 of 47 HPV-associated cases, and this subset also seemed to display a worse patient outcome as compared with the rest of the HPV-associated cohort (OS 16.8 versus 142.8 months, P < .0001). In summary, these findings indicate that TBA is an independent prognostic indicator in VSCC patients, and that high TBA is associated with worse clinical outcomes.

PTEN Loss and ARID1A Mutation in an HPV-positive Metastatic Adenocarcinoma Diagnosed Almost 18 yr After an Intact Cone Excision for Endocervical Adenocarcinoma In Situ.

There have been previous reports of neoplasms with the morphology of endocervical adenocarcinoma in situ (AIS) that secondarily involve the ovaries, presumably through transtubal spread, with a smaller subset metastasizing to distant sites. These ovarian metastases have been discovered up to 7 yr postexcision of the endocervical lesion, consistent with the known potential for overtly invasive cervical carcinomas to recur late after primary curative management. Herein, we present a case of a premenopausal woman with a pelvic mass classified as metastatic human papillomavirus (HPV)-associated endocervical adenocarcinoma (p16-block immunoreactive, high-risk HPV positive by in situ hybridization with PTEN loss, ARID1A, and PBRM1 mutations detected by qualitative next-generation sequencing), identified 17.7 yr (212 mo) after a fertility-sparing cone excision with negative margins for endocervical AIS [HPV-associated, p16-block immunoreactive; PTEN, and BAF250a (ARID1a) expression retained]. Our case highlights: (1) the potential for a subset of lesions with the morphology of AIS to metastasize, and the extraordinarily long timeframe (almost 18 y, the longest reported to date) during which metastases may still be identified; (2) alterations in PTEN and ARID1A may play a role in the progression of a subset of endocervical carcinomas; and (3) the need for studies to evaluate the utility of incorporating ovarian/pelvic imaging into surveillance protocols following fertility-sparing excisions or ovarian-preserving hysterectomies, during the management of endocervical adenocarcinomas, as well as the need to counsel patients about the small but real risk of delayed discovery of ovarian metastases following fertility-preserving surgeries for AIS.

Nonmass enhancement lesions of the breast on core needle biopsy: outcomes, frequency of malignancy, and pathologic findings.

Nonmass enhancement (NME) on breast magnetic resonance imaging (MRI) is defined as an area whose internal enhancement characteristics can be distinguished from the normal surrounding breast parenchyma, without an associated mass in the Breast Imaging Reporting and Data System lexicon. In this study, we evaluated the pathologic correlates of NME lesions of the breast identified on MRI at our institution, including the frequency of atypical or malignant lesions in the core needle biopsies (CNBs), performed after such a radiologic finding. A retrospective study was performed on all CNBs performed for NME on breast MRI between 2010 and 2019. A total of 443 biopsies from 411 patients were identified, comprising 5.5% of all CNBs over the study period. The pathologic diagnoses were benign in the majority of the biopsies (68.0%), whereas 11.5% and 20.5% of the cases were atypical and malignant lesions, respectively. Of the malignant cases, 69.2% were ductal carcinoma in situ (DCIS) and 30.8% were invasive carcinomas. The most common invasive cancer was invasive ductal carcinoma (50%), followed by invasive lobular carcinoma (39.3%). NME identified on breast MRI carried a significant (32%) risk of atypia and malignancy in our cohort, which confirms that biopsy evaluation of these lesions is warranted. DCIS was the most commonly identified malignancy. Notably, among invasive cancers, invasive lobular carcinoma was identified at a substantially higher frequency that would be expected for that histotype.

Pathologic Determination of Multifocality in pT1a1 Squamous Cell Carcinoma of the Cervix: A Retrospective Analysis.

When more than one focus of stromal invasion is present in a superficially invasive cervical squamous cell carcinoma (SCC), determination of the tumoral lateral extent/horizontal extension, and hence tumor-nodes-metastases (TNM) staging, can be problematic. In recent years, a diagnostic approach to distinguish multifocal pT1a1 from pT1b cases has gained increased attention. These criteria call for classifying SCC as multifocal when invasive foci are separated by blocks of uninvolved cervical tissues, and/or are located on separated cervical lips in a tumor that is discontinuous, and/or are situated far apart (≥2 mm) from each other. In this study, we assess our experience with multifocal stage pT1a1 cervical SCC that was retrospectively classified as such using these criteria. Slides from the loop electrosurgical excision or conization specimens, comprising 212 pT1a1, 173 pT1a2, and 206 pT1b cases, were reviewed. Twenty-four (11%) of the 212 pT1a1 cases were classified as multifocal after review. The 24 multifocal pT1a1 cases were compared with the 188 unifocal pT1a1 cases regarding a variety of clinicopathologic parameters. Notably, these 2 groups showed no significant differences regarding all parameters that were evaluated, including patient age, recurrence rate, primary tumoral features in the primary excision specimen (rate of positive margins, median depth of stromal invasion, frequency of lymphovascular invasion), and frequency of residual disease in additional excisions. In summary, we demonstrate comparably favorable patient outcomes in both unifocal and multifocal cases of pT1a1 SCC of the cervix, and, accordingly, we conclusively affirm the validity of the aforementioned criteria for establishing multifocality.

Infectious disorders of the vulva.

The vulva can be affected by a variety of sexually transmitted infections as well as other common infections that are not typically related to sexual transmission. Vulvar infections may adversely affect the quality of life of the patients by causing discomfort and pain. Some of these infections, especially the ulcerative ones, may also increase the risk of transmission of other infectious diseases, including HIV. Due to the recently increasing number of sexually transmitted infections and atypical presentations of these infections in immunocompromised patients, it is important for pathologists to be familiar with histopathologic features of the infectious diseases of the vulva, so that accurate diagnoses can be rendered as promptly as possible. This review discusses the clinicopathologic presentations of the non-HPV related infections of the vulva.

Independent Validation of Tumor Budding Activity and Cell Nest Size as Determinants of Patient Outcome in Squamous Cell Carcinoma of the Uterine Cervix.

A novel 3-tiered grading system that combines tumor budding activity and cell nest size has been found to be highly prognostic in squamous cell carcinomas (SCCs) of various sites, including lung, oral cavity, larynx, hypopharynx, and esophagus. A similar grading system has recently been proposed for SCC of the uterine cervix. In this study, we appraise this grading system in an institutional cohort of cervical SCC to assess its prognostic value in an independent dataset. Our study cohort consisted of 94 consecutive, surgically excised, neoadjuvant therapy-naive cases of SCC of the uterine cervix, stage pT1b or higher. Tumor budding activity and cell nest size were scored on each case, the sum of which formed the basis for assigning a grade in the 3-tiered grading system hereafter referred to as the "tumor budding/nest size" (TBNS) system. As individual variables, both high tumor budding and small nest size were each associated with reduced overall survival (OS), disease-specific survival, and disease-free survival. The full TBNS system was associated with decreased OS, disease-specific survival, and disease-free survival independent of patient age, pathologic stage, and regional lymph node status. TBNS grades 1, 2, and 3 subgroups were clearly distinguishable on multivariate analyses (hazard ratio for OS of 2.06 [95% confidence interval: 0.5-8.42] for grade 2 and 4.58 [95% confidence interval: 1.24-16.87] for grade 3 tumors, relative to their grade 1 counterparts [P=0.035]). Higher grade tumors in the TBNS system were significantly correlated with advanced pathologic stage and lymph node metastasis (P=0.044 and 0.04, respectively). Among the other, potentially prognostic factors, higher pathologic stage, and lymph node metastasis were associated with decreased OS (P<0.001 and 0.004, respectively), whereas keratinization, nuclear size, mitotic count, and World Health Organization (WHO) grade were not. In conclusion, the proposed TBNS grading system is an excellent prognostic indicator that may potentially provide information that is useful in clinical decision-making. Our findings validate the previous study that proposed this system for prognostically stratifying cervical SCC patients. If further confirmed, consideration should be given to routinely adding a TBNS grade to pathologic descriptions of cervical SCC.

The significance of recurrence in endometrial polyps: a clinicopathologic analysis.

A subset of endometrial polyps recurs after resection. The clinicopathologic significance of the phenomenon is evaluated herein. Consecutive cases of recurrent polyps (index polyp removed by hysteroscopy-directed polypectomy or by curettage; at least one more polyp diagnosed ≤12 months after) were compared with an age-matched control group of nonrecurrent polyps regarding 15 clinicopathologic features. A total of 107 (5.6%) of the 1908 polyps diagnosed in a sampling specimen during the study period was a recurrence, and 102 (6.9%) of the 1478 patients who were diagnosed with an endometrial polyp in a sampling specimen had at least 1 recurrence. Eighty-six percent of patients with any recurrences had only one recurrence, with a mean duration between the index polyp and the first recurrence of 4.36 months. On univariate analyses, the recurrent polyps were, compared with controls, significantly larger, had a higher stromal mitotic index, and more frequently displayed prominent thick-walled vessels in most fragments of the polyp. However, on Cox regression multivariate analyses, no single clinicopathologic feature was significantly associated with a recurrence. No malignancies were diagnosed during the follow-up of the study and control group patients at median follow-up durations of 23 and 34 months, respectively. In conclusion, the recurrence of an endometrial polyp is relatively uncommon (5.6% of polyps) and does not portend an increased risk of malignancy. We could not identify any clinicopathologic features that conclusively predict a recurrence.

Normal human lymph node T follicular helper cells and germinal center B cells accessed via fine needle aspirations.

Germinal centers (GC) are critically important for maturation of the antibody response and generation of memory B cells, processes that form the basis for long-term protection from pathogens. GCs only occur in lymphoid tissue, such as lymph nodes, and are not present in blood. Therefore, GC B cells and GC T follicular helper (TFH) cells are not well-studied in humans under normal healthy conditions, due to the limited availability of healthy lymph node samples. We used a minimally invasive, routine clinical procedure, lymph node fine needle aspirations (LN FNAs), to obtain LN cells from healthy human subjects. This study of 73 LNs demonstrates that human LN FNAs are a safe and feasible technique for immunological research, and suggests benchmarks for human GC biology under noninflammatory conditions. The findings indicate that assessment of the GC response via LN FNAs will have application to the study of human vaccination, allergy, and autoimmune disease.

Recurrent Pleomorphic Myxoid Liposarcoma in a Patient With Li-Fraumeni Syndrome.

Pleomorphic myxoid liposarcoma is an extremely rare, clinically aggressive subtype of liposarcoma that has been primarily reported in young patients. In this article, we report a case of a pleomorphic myxoid liposarcoma that presented as a second primary neoplasm in a 34-year-old man with history of primary mediastinal large B-cell lymphoma. During the clinical workup, the patient was diagnosed with a germline TP53 gene mutation and Li-Fraumeni syndrome. The tumor, a 2.9 × 2.3 × 2.0 cm well-demarcated and solid mass, was centered in the anterior chest wall soft tissue. Histologically, most of the tumor displayed abundantly myxoid stroma, low cellularity of mostly bland spindle cells, delicate branching capillaries, and lipoblasts; these areas transitioned to small areas whose features were reminiscent of pleomorphic liposarcoma. As assessed by fluorescence in situ hybridization, the tumor showed no DDIT3 (CHOP) (12q13) rearrangements or MDM2 gene amplification. Clinically, the tumor progressed with multiple recurrences and metastasis to the humerus bone. To our knowledge, this is the first case of pleomorphic myxoid liposarcoma diagnosed in an adult with Li-Fraumeni syndrome.

Intranodal palisaded myofibroblastoma of para-esophageal lymph node: Case report with cytologic and histologic findings.

Intranodal palisaded myofibroblastoma is a rare lymph node mesenchymal neoplasm that most commonly arises in inguinal lymph nodes. There is limited data about cytologic features of this tumor and its diagnostic pitfalls. The combination of bland appearing spindle cells, fibrillary matrix, and hemosiderin pigments are the characteristic features of this neoplasm in cytologic specimens.

Osteosarcomatous Divergence in Dedifferentiated Liposarcoma Presenting as a Colonic Mass.

Dedifferentiated liposarcomas most commonly arise in the retroperitoneum, accounting for 10% of liposarcomas. Heterologous differentiation occurs in 5-10% of dedifferentiated liposarcomas; however, divergent osteosarcomatous differentiation is rare. We report a rare case of initial presentation of dedifferentiated liposarcoma with osteosarcomatous component as a colonic mass in a 72-year-old man. The tumor is mainly composed of bony trabeculae with intervening highly atypical cells and adjacent high-grade mesenchymal nonlipogenic tumor, as well as areas of well-differentiated liposarcoma. Immunohistochemical studies showed diffuse positivity for SATB2 in the atypical cells and fluorescence in situ hybridization revealed high-level amplification of MDM2 gene, supporting the diagnosis of well-differentiated and dedifferentiated liposarcoma with heterologous osteosarcomatous differentiation.

Breast cancers with a HER2/CEP17 ratio of 2.0 or greater and an average HER2 copy number of less than 4.0 per cell: frequency, immunohistochemical correlation, and clinicopathological features.

The 2013 American Society of Clinical Oncology and College of American Pathologists (ASCO/CAP) guidelines classified breast cancers with a fluorescence in situ hybridization dual-probe HER2/CEP17 ratio of 2 or greater as "amplified," inclusive of cases with a HER2 copy number less than 4. The 2018 ASCO/CAP update assigns HER2/neu status for the latter group in a fashion that is highly dependent on the associated immunohistochemical findings. Herein, the authors define the frequency, immunohistochemical correlates, and other clinicopathological features of breast cancers with HER2/CEP17 ratio of 2 or greater and HER2/neu copy number less than 4 (group A), based on an analysis of an institutional cohort assessed for HER2/neu status by both florescence in situ hybridization and immunohistochemistry and scored using 2013 ASCO/CAP criteria. Group A cases were compared with a group B of HER2/neu-amplified breast cancers with a HER2/neu copy number of 4 or greater regarding a variety of clinicopathological features. One hundred sixty-nine (14%) of 1201 cases were HER2/neu amplified, 18 (10.7%) in group A and 151 (89.3%) in group B. By immunohistochemistry, 61.1% of group A cases were HER2/neu negative, 7 (38.9%) were equivocal, and none were positive. In contrast, 66.9% of group B cases were HER2 positive (3+). We could not demonstrate statistically significant differences between the 2 groups regarding standard clinicopathological variables. In summary, our group A cases account for 1.5% of breast cancers, and 10.7% of all HER2/neu-amplified cancers classified as such based on 2013 ASCO/CAP criteria. They are predominantly HER2/neu negative by immunohistochemistry, which suggests that they are biologically different from classically HER2/neu-amplified cases and which validates the 2018 ASCO/CAP guideline against automatically classifying such cases as HER2/neu amplified.