Predictors of Outcome in Mammary Adenoid Cystic Carcinoma: A Multi-Institutional Study

Salivary gland-like tumors of the breast: Histopathologic and genetic features with clinical implications

Salivary gland-like tumors of the breast are rare neoplasms that share morphologic, immunophenotypic, and/or genetic features with their salivary gland counterparts, highlighting a shared underlying histopathogenesis in most cases. Salivary gland-like carcinomas included in the World Health Organization classification of breast tumors are adenoid cystic carcinoma, secretory carcinoma, mucoepidermoid carcinoma, acinic cell carcinoma, and the exceedingly rare polymorphous adenocarcinoma. These carcinomas are usually triple negative for estrogen receptor and progesterone receptor expression and HER2 overexpression, yet generally have favorable prognosis, in contrast to high-grade triple negative carcinomas of no special type. On the other hand, a small subset, such as solid-basaloid adenoid cystic carcinoma, rare high-grade carcinomas, and those associated with transformation to other types of high-grade invasive carcinoma can behave more aggressively. Other salivary gland-like tumors of the breast, such as pleomorphic adenoma and adenomyoepithelioma, are usually benign but can rarely undergo malignant transformation. Although clinical experience with salivary gland-like breast tumors is overall limited, their recognition and accurate classification has important implications for prognosis and clinical management, especially to avoid overtreatment of salivary gland-like carcinomas. The identification of characteristic genetic alterations and/or immunohistochemical surrogates in many of these tumors has practical applications to establishing an accurate diagnosis and directing clinical management. This review highlights the histopathologic and genetic characteristics of salivary gland-like breast tumors and the implications of the diagnosis for current clinical management.

Breast Cancer Histopathology in the Age of Molecular Oncology

For more than a century, microscopic histology has been the cornerstone for cancer diagnosis, and breast carcinoma is no exception. In recent years, clinical biomarkers, gene expression profiles, and other molecular tests have shown increasing utility for identifying the key biological features that guide prognosis and treatment of breast cancer. Indeed, the most common histologic pattern-invasive ductal carcinoma of no special type-provides relatively little guidance to management beyond triggering grading, biomarker testing, and clinical staging. However, many less common histologic patterns can be recognized by trained pathologists, which in many cases can be linked to characteristic biomarker and gene expression patterns, underlying mutations, prognosis, and therapy. Herein we describe more than a dozen such histomorphologic subtypes (including lobular, metaplastic, salivary analog, and several good prognosis special types of breast cancer) in the context of their molecular and clinical features.

Prognosis of primary breast salivary gland-type carcinoma: a propensity score-matching analysis with invasive carcinoma of no special type based on the SEER database for years 2010-2020

BACKGROUND

Primary breast salivary gland-type carcinoma has weak evidence to support its management due to its rare occurrence and limited data regarding its clinicopathological features and prognosis. Therefore, this study aimed to assess clinicopathological features and prognosis for this type of carcinoma diagnosed over the past decade and compared those to the common breast invasive carcinoma of no special type (NST).

METHODS

This study used the Surveillance, Epidemiology, and End Results (SEER) database to extract data regarding primary breast salivary gland-type carcinoma. Using a propensity score-matching approach, the prognosis was compared with invasive carcinoma, NST.

RESULTS

This study included 488 cases of salivary gland-type carcinoma and 375,660 cases of invasive carcinoma, NST, giving an occurrence ratio of 1 to 770. Adenoid cystic carcinoma (81%) formed the majority of salivary gland-type carcinoma, followed by secretory carcinoma (13%). For salivary gland-type carcinoma, acinic cell carcinoma histological type, tumor grade 3, HER2-overexpressed status, and higher AJCC stage groups were significant worse prognostic factors for breast cancer-specific survival in univariate analyses (p < 0.05). Nonetheless, tumor grade 3 and higher AJCC stage groups remained as significant independent prognostic factors in multivariate analysis (p < 0.05). The apparent better breast cancer-specific survival of salivary gland-type carcinoma as compared to that of invasive carcinoma, NST, was diminished following adjustment for differences in baseline clinicopathological features and treatment-related variables.

CONCLUSIONS

This study suggests that when managing primary breast salivary gland-type carcinoma, greater emphasis should be given to the tumor grade and AJCC stage group in addition to acinic cell carcinoma histological type and HER2 overexpression. Conventional prognostic factors are important as salivary gland-type carcinoma had similar prognosis as invasive carcinoma, NST, following adjustment for confounding variables.

Solid-Basaloid Adenoid Cystic Carcinoma of the Breast: An Aggressive Subtype Enriched for Notch Pathway and Chromatin Modifier Mutations With MYB Overexpression

Adenoid cystic carcinoma (AdCC) is a rare triple-negative breast cancer analogous to its extramammary counterparts. Diagnosis of the more aggressive solid-basaloid variant of AdCC (SB-AdCC) can be challenging due to poorly defined histopathologic and molecular features. We characterized 22 invasive and in situ basaloid carcinomas by morphology, immunohistochemistry, genetics, and MYB status using multiple platforms and assessed clinical behavior and neoadjuvant chemotherapy responses. After consensus review, 16/22 cases were classified as SB-AdCC. All SB-AdCC had predominantly solid growth and at least focal myxohyaline stroma and were immune-poor. Eosinophilic squamoid cells (69%, 11/16) and basement membrane-like secretions (69%, 11/16) were common, and intercalated ducts (31%, 5/16) were less frequent. SB-AdCC typically expressed SOX10 (100%, 16/16) and luminal markers (100%, 16/16 CK7; 88%, 14/16 CD117; 93%, 13/14 CAM5.2). SMA (40%, 6/15) expression was less common, and SMM (27%, 3/11), GATA3 (20%, 3/15), and p63 (25%, 4/16) were mostly negative. MYB protein and/or MYB RNA overexpression was universal in evaluable cases (13/13), with RNA in situ hybridization (10/10) more reliable than immunohistochemistry (10/11, plus 4 excisions inconclusive). Fluorescence in situ hybridization and/or next-generation sequencing identified MYB rearrangements (20%, 3/15) and amplifications/copy gains (60%, 9/15) but no MYB::NFIB fusions. SB-AdCC often had aberrations in Notch pathway (60%, including 40% NOTCH1 and 20% NOTCH2) and/or chromatin modifier (60%, including 33% CREBBP) genes, with relatively infrequent TP53 mutations (27%). Unclassified invasive basaloid carcinomas lacking described histologic features of SB-AdCC (n = 4) and basaloid ductal carcinoma in situ (n = 2) showed similar immunoprofiles and genetics as SB-AdCC, including Notch aberrations and MYB overexpression with MYB rearrangements/amplifications. Overall, nodal (22%) and distant (33%) metastases were common, and 23% of patients died of disease (mean follow-up, 35 months; n = 22). Responses were poor in all 7 neoadjuvant chemotherapy-treated patients, without any achieving pathologic complete response. The data highlight the histopathologic spectrum of basaloid carcinomas including SB-AdCC and reveal shared genetics and MYB activation, which can be diagnostically useful. Aggressive behavior and poor treatment responses emphasize a need for additional treatment approaches.

The Role of Novel Immunohistochemical Markers for Special Types of Breast Carcinoma

Some histologic special types of breast carcinoma harbor specific recurrent genetic alterations that are not seen in other types of breast carcinoma (no special type), namely adenoid cystic carcinoma, secretory carcinoma, and tall cell carcinoma with reversed polarity. These tumors have unique morphologic features, are triple-negative, that is, do not express hormone receptors or HER2, and are generally associated with a favorable prognosis. Adenoid cystic carcinoma, like its counterpart in other organs, shows a MYB-NFIB fusion gene that is the result of a recurrent t(6;9)(q22-23;p23-24) translocation. Other MYB alterations have been described that result in overexpression of MYB . Secretory carcinoma is characterized by an ETV6-NTRK3 gene fusion that is the result of recurrent (12;15);(p13;q25) translocation, which is also seen in mammary analog secretory carcinoma of the salivary gland. Tall cell carcinoma with reversed polarity shows IDH2 p.Arg172 hotspot mutations. Immunohistochemical antibodies have emerged that identify the underlying genetic alterations in these tumors and serve as useful diagnostic tools. This review will provide an update on the molecular features and diagnostic immunohistochemical markers that have become increasingly popular to aid in diagnosing these uncommon triple-negative breast tumors.

Solid-basaloid variant of adenoid cystic carcinoma of the breast unresponsive to neoadjuvant chemotherapy: Case report

INTRODUCTION AND IMPORTANCE

Adenoid cystic carcinoma (ACC) is a rare triple-negative breast cancer, accounting for only 0.1 % of all primary breast carcinomas. At variance with the classic variant, the solid-basaloid variant of ACC (SB-ACC) is clinically more aggressive and has different molecular features. There is, currently, no consensus regarding the treatment of SB-ACC of the breast, especially the use of neoadjuvant chemotherapy.

CASE PRESENTATION

Here, we present a rare case of SB-ACC in an elderly female patient, with no history of breast carcinoma, who presented with a 4.5 cm central round mass invading the nipple. Given the locally advanced triple negative breast cancer and the invasion of the nipple-areolar complex, the patient has received neoadjuvant chemotherapy followed by surgical treatment. On histopathological examination, the diagnosis of SB-ACC, non-responsive to neoadjuvant chemotherapy, with absence of rearrangement of the MYB gene was retained. The patient received adjuvant radiation therapy and was ambulatory followed without recurrence at the 12-month follow-up.

DISCUSSION/CONCLUSION

This case provided direct evidence that SB-ACC of the breast wasn't responsive to neoadjuvant chemotherapy but cannot allow for definitive conclusions on chemotherapy recommendations. For this reason, more data must be published to investigate the real value of neoadjuvant chemotherapy in SB-ACC.

Salivary Gland-like Tumors of the Breast

CONTEXT

The World Health Organization classification of tumors of the breast recognizes several special type carcinomas and benign lesions with features comparable to those of salivary gland tumors.

OBJECTIVE

To discuss the histologic, immunophenotypic, molecular, and clinical features of salivary gland-like carcinomas of the breast. These breast tumors are often negative for hormone receptors and human epidermal growth factor receptor 2 (HER2), that is, triple-negative, but they generally have a much better prognosis than triple-negative breast carcinomas of no special type. We compare the immunophenotypic, molecular, and clinical features of these breast tumors with their salivary gland counterparts, highlighting similarities and differences. We also discuss benign salivary gland-like breast tumors. Finally, we highlight recent developments in understanding the molecular pathogenesis of these breast tumors and novel ancillary studies that can be used to support their diagnosis.

DATA SOURCES

A literature review was conducted, and papers were selected for further analysis and discussion by the authors of this review based on their novelty, applicability, and impact in the field.

CONCLUSIONS

Breast tumors that exhibit morphologic overlap with salivary gland tumors have been recognized by pathologists for decades, but the similarities and differences in their molecular pathogenesis have not been understood until more recently. These developments have led to novel diagnostic tools and further knowledge of these rare breast lesions.

Breast Cancer Pathology in the Era of Genomics

The era of genomic medicine provides an opportunity for pathologists to offer greater detail about the molecular underpinnings of a patient's cancer and thereby more targeted therapeutic options. In this review article, the role of genomics in breast cancer pathology is discussed, as it pertains to risk management, classification of special tumor types, predictive and prognostic testing, identification of actionable therapeutic targets, and monitoring for disease progression or development of treatment resistance.

Clinicopathologic Predictors of Clinical Outcomes in Mammary Adenoid Cystic Carcinoma: A Multi-institutional Study

Adenoid cystic carcinoma (AdCC) is an uncommon type of invasive breast carcinoma with a favorable prognosis. However, some cases are aggressive. The study aims to define the clinicopathologic predictors of outcome. Clinical, radiological, and pathologic variables were recorded for 76 AdCC cases from 11 institutions. The following histologic characteristics were evaluated by the breast pathologist in each respective institution, including Nottingham grade (NG), percentages of various growth patterns (solid, cribriform, trabecular-tubular), percentage of basaloid component, tumor borders (pushing, infiltrative), perineural invasion, lymphovascular invasion, necrosis, and distance from the closest margin. Various grading systems were evaluated, including NG, salivary gland-type grading systems, and a new proposed grading system. The new grading system incorporated the growth pattern (percent solid, percent cribriform), percent basaloid morphology, and mitotic count using the Youden index criterion. All variables were correlated with recurrence-free survival. Nineteen (25%) women developed local and/or distant recurrence. Basaloid morphology (≥25% of the tumor) was identified in 20 (26.3%) cases and a solid growth pattern (using ≥60% cutoff) in 22 (28.9%) cases. In the univariate analysis, the following variables were significantly correlated with worse recurrence-free survival: solid growth pattern, basaloid morphology, lymphovascular invasion, necrosis, perineural invasion, and pN-stage. In the multivariate analysis including basaloid morphology, pN-stage, lymphovascular invasion, and perineural invasion, basaloid morphology was statistically significant, with a hazard ratio of 3.872 (95% CI, 1.077; 13.924; P =.038). The NG and the new grading system both correlated with recurrence-free survival. However, grade 2 had a similar risk as grade 3 in the NG system and a similar risk as grade 1 in the new grading system. For solid growth patterns and basaloid morphology, using a 2-tier system with 1 cutoff was better than a 3-tier system with 2 cutoffs. Basaloid morphology and solid growth pattern have prognostic values for AdCC, with a 2-tier grading system performing better than a 3-tier system.

Breast lesions with myoepithelial phenotype

Myoepithelial cells (MECs) constitute a continuous layer of cells surrounding the breast glands, localised between the epithelial cells (ECs) and the basal membrane. MECs play important roles in normal mammary gland as they produce basal membrane and stimulate secretion. During neoplastic transformation, MECs act as a barrier preventing stromal invasion. MECs themselves can undergo a great variety of changes, ranging from hyperplastic to metaplastic, to neoplastic, and giving rise to a wide spectrum of morphological pictures sometimes difficult to interpret on routine diagnoses. Several benign and malignant breast tumours can present features of MECs differentiation. As these latter tumours are quite infrequent, the purpose of the present study is to offer a review of the morphological spectrum of MECs lesions, with correlations to prognosis.

Adenoid Cystic Carcinoma of the Breast: Radiologic-Pathologic Correlation

Adenoid cystic carcinoma (ACC) is an uncommon malignancy occurring most frequently in the salivary glands. Breast ACC is rare. Pain is common at the site of ACC; otherwise, presentation is similar to other primary breast cancers. Adenoid cystic carcinomas classically lack calcifications; the imaging manifestations of ACC are otherwise highly variable, likely related to multiple pathologic growth patterns. While ACC in other regions of the body tends to be more aggressive, ACC involving the breast typically has less aggressive biologic characteristics. Classic-type breast ACC has a lower tendency to recur locally with radiation, metastasize to regional lymph nodes, and spread to other parts of the body. Perineural spread of disease can be seen but is not common. The rarer solid basaloid-type has a higher tendency for local or distant spread and recurrence. Although ACC is usually triple receptor-negative (estrogen receptor, progesterone receptor, human epidermal growth factor-2 receptor), the indolent nature of this tumor dictates its management. With classic-type ACC, the inclusion of axillary surgery has no consensus and the use of chemotherapy or hormonal therapy is rare. Axillary nodal surgery and chemotherapy are often included in management of the more aggressive solid basaloid-type. An understanding of the breast imaging, histopathology, and clinical course is key for appropriate treatment and follow-up of ACC.

Solid-basaloid variant of adenoid cystic carcinoma of the breast with near complete response to neoadjuvant chemotherapy

Breast adenoid cystic carcinoma (AdCC) is a rare subtype of triple negative breast cancer. Two morphologic variants are described, namely classic AdCC (C-AdCC) and solid basaloid (SB-AdCC). Recent studies have shown that the SB-AdCC variant has significantly worse prognosis than C-AdCC. Due to the rarity of SB-AdCC, no standard recommendations are available for its management. Data on the use and benefit of chemotherapy in patients with SB-AdCC are sparse and the response to neoadjuvant chemotherapy has not been reported. We present the clinical and pathologic findings of a patient with SB-AdCC treated with neoadjuvant chemotherapy who achieved a remarkable pathologic response.

Adenoid Cystic Carcinoma of the Breast May Be Exempt from Adjuvant Chemotherapy

Consistent standards regarding whether postoperative adjuvant chemotherapy is required in the treatment of adenoid cystic carcinoma of the breast (ACCB) are currently lacking. Using clinical data from the Surveillance, Epidemiology, and End Results (SEER) database (1988−2015), and the National Cancer Center of China (2004−2020), we retrospectively analyzed patients with ACCB who received radical treatment. A total of 661 patients were eligible. The median age at diagnosis was 61 years; 99.5% of patients were initially diagnosed with stage I and II breast cancer, and 76.7% had triple-negative breast cancer. Only 12.4% of patients received adjuvant chemotherapy. Multivariate analysis showed that patients with lymph node metastasis and non-radiotherapy had worse overall survival (OS) (p < 0.05). Patients with lymph node metastasis, stage IIB and III, histological grade ≥ 2, and non-radiotherapy had worse breast cancer-specific survival (BCSS) (p < 0.05). Adjuvant chemotherapy did not improve the OS or BCSS. Patients treated with adjuvant chemotherapy also had no better survival outcomes after propensity score matching. External data verification confirmed that chemotherapy did not improve disease-free survival or OS. Adjuvant chemotherapy cannot improve the clinical outcomes of ACCB, even in subgroups with a high risk of recurrence and metastasis.

Adenoid Cystic Carcinoma of the Breast in a Male Patient: A Case Report and Literature Review

Adenoid cystic carcinoma (ACC) of the breast (breast ACC) is a rare tumor, especially in men, with only 17 cases reported in the literature. Owing to this rarity, male breast ACC is susceptible to missed or incorrect diagnoses, and data on treatment options and prognosis is also scarce. Herein, we report a case of a male patient with primary breast ACC and performed a detailed clinicopathological analysis of the 17 cases reported in the literature. A 38-year-old Chinese man patient developed right-sided breast nipple retraction in 2013 and presented to our hospital in 2015 with a palpable mass in the right breast for four days. B-scan ultrasound indicated the presence of a solid space-occupying lesion in the right breast. Breast Imaging Reporting and Data System (BI-RADS) classified the lesion as category 4B, and mammography showed a right breast nodule classified as BI-RADS 4C. Modified radical mastectomy for breast cancer was performed on the right breast. Microscopic examination of the excised tissue revealed diffuse tumor invasion of the subcutaneous fibers and adipose tissue, with tumor cells arranged in cribriform, tubular, and microcystic patterns. Immunohistochemical staining indicated that the glandular epithelial cells were positive for CD117, CK7, and Ki67 (approximately 30%) and negative for estrogen receptor, progesterone receptor, and human epidermal growth factor receptor 2, while the myoepithelial/basal cells were positive for P63, CK5/6 and S-100. Moreover, basement membrane materials were positive for collagen type IV. Molecular pathology analysis by fluorescence in situ hybridization revealed that the tumor was negative for MYB rearrangements. The patient was followed up for 82 months with no tumor recurrence or metastasis. According to the current literature, mastectomies have a better prognosis than lumpectomy. Accurately identifying the diagnosis of male breast ACC and considering the surgery of mastectomy may be the key factors for patients to obtain a good prognosis based on the microscopic characteristics of the tumor.

Distinct clinicopathological and genomic features in solid and basaloid adenoid cystic carcinoma of the breast

Adenoid cystic carcinoma (AdCC) of the breast is a rare indolent carcinoma of salivary gland-type tumors, frequently associated with MYB genetic alteration. Solid and basaloid adenoid cystic carcinoma (SB-AdCC) is considered a sparse variant of AdCC. This study sought to search for clinicopathological and genomic features in SB-AdCC. Registered clinicopathological data on a cohort of 13 AdCC of the breast cases, including six conventional adenoid cystic carcinoma (C-AdCC) cases and seven SB-AdCC cases, were collected. MYB gene rearrangement via fluorescent in situ hybridization was investigated and MYB protein expression was evaluated by immunohistochemistry. Compared with C-AdCC, we found that the distribution of SB-AdCC cases were shifted to older age and were more frequently distant metastasis. Moreover, metastasis cases also showed a high (exceed 30%) Ki-67 index. Both groups showed MYB rearrangements and MYB protein expression, but they were less frequent in SB-AdCC than C-AdCC. To conclude, our results suggest that SB-AdCC is an aggressive variant of mammary AdCC with a higher incidence of distant metastases compared with C-AdCC, though they share common molecular features. A high Ki-67 index may be an adverse prognostic factor for metastasis.

The clinical behavior and genomic features of the so-called adenoid cystic carcinomas of the solid variant with basaloid features

Classic adenoid cystic carcinomas (C-AdCCs) of the breast are rare, relatively indolent forms of triple negative cancers, characterized by recurrent MYB or MYBL1 genetic alterations. Solid and basaloid adenoid cystic carcinoma (SB-AdCC) is considered a rare variant of AdCC yet to be fully characterized. Here, we sought to determine the clinical behavior and repertoire of genetic alterations of SB-AdCCs. Clinicopathologic data were collected on a cohort of 104 breast AdCCs (75 C-AdCCs and 29 SB-AdCCs). MYB expression was assessed by immunohistochemistry and MYB-NFIB and MYBL1 gene rearrangements were investigated by fluorescent in-situ hybridization. AdCCs lacking MYB/MYBL1 rearrangements were subjected to RNA-sequencing. Targeted sequencing data were available for 9 cases. The invasive disease-free survival (IDFS) and overall survival (OS) were assessed in C-AdCC and SB-AdCC. SB-AdCCs have higher histologic grade, and more frequent nodal and distant metastases than C-AdCCs. MYB/MYBL1 rearrangements were significantly less frequent in SB-AdCC than C-AdCC (3/14, 21% vs 17/20, 85% P < 0.05), despite the frequent MYB expression (9/14, 64%). In SB-AdCCs lacking MYB rearrangements, CREBBP, KMT2C, and NOTCH1 alterations were observed in 2 of 4 cases. SB-AdCCs displayed a shorter IDFS than C-AdCCs (46.5 vs 151.8 months, respectively, P < 0.001), independent of stage. In summary, SB-AdCCs are a molecularly heterogeneous but clinically aggressive group of tumors. Less than 25% of SB-AdCCs display the genomic features of C-AdCC. Defining whether these tumors represent a single entity or a collection of different cancer types with a similar basaloid histologic appearance is warranted.

Male Adenoid Cystic Carcinoma of the Breast

Adenoid cystic carcinoma (ACC) of the breast, a rare malignancy that makes up less than 0.1% of all breast malignancies, is much rarer in males than in females. Due to the rarity of this disease, an optimal treatment strategy for male breast ACC has not been established, and therapy for male patients is currently based on guidelines for female patients. According to previous reported cases, some authors believe that male breast ACC may have higher invasive potential than female breast ACC and the prognoses in male patients may be worse than those in female patients. Therefore, a more proactive diagnosis and treatment regimen may be required. However, the clinical feature of our case is inconsistent with this view. Herein we report the case of a 24-year-old male without any antecedent medical or family history who presented with a slow-growing lump on his left chest wall for 5 years. The patient initially underwent lumpectomy, and the mass was pathologically diagnosed as breast ACC. Systemic examination was performed, and no evidence of distant metastasis was found. Then, he received modified radical mastectomy and ipsilateral axillary lymph node dissection. The mastectomy pathological examination revealed that no cancerous tissue was detected around the primary tumor bed, and all 22 axillary lymph nodes were negative. The patient did not receive postoperative chemotherapy, radiotherapy or endocrine therapy and remained well after 28 months of follow-up. In this study, we review the literature and summarize the clinical manifestations, imaging and histopathological characteristics, treatments and outcomes of male breast ACC. We share our experience in the hopes that this evidence will aid in the development of better therapeutics.

Dominant cell type analysis predicts head and neck adenoid cystic carcinoma outcomes

Traditional histological grading for predicting adenoid cystic carcinoma (ACC) outcomes is challenging and unreliable. We explored the relationship between dominant cell type (DCT) and outcomes for ACC of the head and neck to develop a new approach to predicting prognosis. Clinicopathological data were obtained from a retrospective cohort of 167 patients with primary ACC of the head and neck. Using immunohistochemistry markers to determine DCT, tumors were subclassified into three distinct subtypes, epithelial-predominant (E-ACC), myoepithelial-predominant (M-ACC), and conventional (C-ACC). Differences in clinicopathological parameters and clinical outcomes among these subtypes were then analyzed. Compared to that of M-ACC and C-ACC, E-ACC exhibited more aggressive clinicopathological features with predominantly solid components, high-grade transformation, lymphovascular invasion, tumor necrosis (TN), Ki-67 ≥ 30%, and advanced stage of disease. Both E-ACC and M-ACC could present as solid morphological forms, but E-ACC had a significantly worse prognosis than M-ACC. DCT, TN, and disease stage were independent predictors of recurrence-free survival. DCT, TN, age ≥ 50 years, and disease stage were independent predictors for overall survival. In conclusion, DCT was an independent prognostic indicator for both recurrence-free and overall survival for ACC. Our results provide a new approach to predicting prognosis in ACC and a strong pathological basis for clinically optimizing treatment.

Triple-Negative Breast Cancer Histological Subtypes with a Favourable Prognosis

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.

Adenoid cystic carcinoma and basaloid carcinoma of the breast: A clinicopathological study

Adenoid cystic carcinoma of the breast (ACCB) is a rare triple negative tumor (TNT) with an excellent prognosis in most cases. Three different histologic types are recognized: classic ACCB, solid basaloid ACCB (SB-ACCB), and ACCB with high-grade transformation. A majority of these tumors show characteristic molecular and immunohistochemical (IHC) features, with fusion of MYB and NFIB genes and overexpression of MYB, respectively. Basaloid carcinomas of the breast (BCB) are infrequently described. They resemble SB-ACCB and TNT of no special type (TNT-NST). We have studied the clinicopathological features of 17 ACCB and 9 BCB, investigating the expression of MYB by IHC and the rearrangements of MYB by fluorescence in situ hybridization (FISH). MYB was expressed by IHC in 15 ACCB and in 3 BCB. MYB FISH detected rearrangements in 11 ACCB and in 2 BCB. After a mean follow-up of 90 months, with a range of 12-204 months, 2 patients with ACCB with high-grade transformation and 1 patient with BCB developed metastases and died of disease. In summary, most ACCB have a good prognosis, but tumors with adverse histopathological features may metastasize. BCB may overlap with ACCB and TNT-NST, and their prognosis should be further studied.

MYB Translocations in Both Myoepithelial and Ductoglandular Epithelial Cells in Adenoid Cystic Carcinoma: A Histopathologic and Genetic Reappraisal in Six Primary Cutaneous Cases

ABSTRACT

Adenoid cystic carcinoma (ACC) is an infiltrating carcinoma composed of 2 cell types, myoepithelial and ductoglandular epithelial cells. Although approximately 70% of ACC exhibit translocations of the MYB proto-oncogene or MYB proto-oncogene like 1 (MYBL1), expression of MYB is known to be limited in myoepithelial cells. We investigated the histopathologic and genetic characteristics of ACC in 6 primary cutaneous cases. Histopathologically, 3 cases (50%) exhibited well-demarcated nodules composed of large nests, easily misdiagnosed as polymorphous sweat gland carcinoma. Two cases (33%) harbored large cystic structures resembling spiradenoma, hidradenoma, and digital papillary adenocarcinoma. A papillary pattern was focally observed in 2 cases (33%). A melting phenomenon within the myxoid stroma was seen in one case (17%). Fluorescence in situ hybridization (FISH) revealed MYB break-apart in 3 cases (50%). A combined FISH and immunohistochemical method revealed MYB break-apart signals in both p63-positive myoepithelial and p63-negative ductoglandular epithelial cells, suggesting that both cell types constitute elements of the tumor in ACC. Moreover, we established a well-circumscribed variant of ACC and proposed 3 new patterns of cystic, papillary, and melting in addition to the 3 patterns of cribriform, tubular, and solid growth.

Problematic breast tumors reassessed in light of novel molecular data

Breast cancer is a vastly heterogeneous disease encompassing a panoply of special histological subtypes. Although rare breast tumors have largely not been investigated systematically in large scale genomics series, recent studies have shed light on the genetic underpinnings of special histologic subtypes of breast cancer. Genomic analyses of estrogen receptor-positive special histologic types of breast cancer have not resulted in the identification of novel pathognomonic genetic alterations in addition to the confirmation of the presence of CDH1 loss-of-function mutations in invasive lobular carcinomas. By contrast, the analyses of triple-negative breast cancers have demonstrated that low-grade triple-negative breast cancers categorically differ from the common forms of high-grade triple-negative disease biologically and phenotypically and are underpinned by specific fusion genes or hotspot mutations. A subset of low-grade triple-negative disease has been shown to harbor highly recurrent if not pathognomonic genetic alterations, such as ETV6-NTRK3 fusion gene in secretory carcinomas, the MYB-NFIB fusion gene, MYBL1 rearrangements or MYB gene amplification in adenoid cystic carcinomas, and HRAS Q61 hotspot mutations coupled with mutations in PI3K pathway genes in estrogen receptor-negative adenomyoepitheliomas. A subset of these pathognomonic genetic alterations (e.g., NTRK1/2/3 fusion genes) now constitute an FDA approved indication for the use of TRK inhibitors in the advanced/metastatic setting. These studies have also corroborated that salivary gland-like tumors of the breast, other than acinic cell carcinomas, harbor the repertoire of somatic genetic alterations detected in their salivary gland counterparts. Reassuringly, the systematic study of special histologic types of breast cancer utilizing state-of-the-art sequencing approaches, rather than rendering pathology obsolete, has actually strengthened the importance of breast cancer histologic typing and is providing additional ancillary markers for the diagnosis of these rare but fascinating entities.

Salivary gland-type mammary carcinoma arising in microglandular adenosis: A case report and clinicopathological review of the literature

INTRODUCTION

Microglandular adenosis (MGA) is a rare benign proliferative lesion lacking a myoepithelial cell layer; 27% of all reported cases have progressed to invasive carcinoma. Salivary gland-type carcinomas of the breast are also uncommon, representing 2% of all breast cancers. This wide spectrum of neoplasms tends to be triple negative and generally has an excellent prognosis. Given the rarity of salivary gland-type carcinomas of the breast arising from MGA, there are few reports of these cases in literature. As such, there is uncertainty regarding their diagnosis and treatment strategies.

PRESENTATION OF CASE

We report the rare case of a 66-year-old woman who presented with a triple negative, invasive carcinoma with salivary gland-type features, arising from MGA. The patient underwent mastectomy with sentinel lymph node biopsy, followed by Taxotere and Cyclophosphamide (TC) chemotherapy and 50 Gy in 25 fractions of radiation to her chest wall. We reviewed the available literature on salivary gland-type breast carcinomas arising from MGA.

DISCUSSION

Despite the generally unfavourable characteristics associated with carcinoma arising in microglandular adenosis (MGACA), most patients with MGACA have favourable outcomes.

CONCLUSIONS

The findings of the present case and reviewed cases are consistent with the literature on MGA, atypical MGA (AMGA), and MGACA. Future study of this rare entity is warranted to establish a consensus surrounding its clinical significance and treatment methods.

Fine-needle aspiration cytology for the diagnosis of solid basaloid adenoid cystic carcinoma of the breast: Its role, limitation, and perspective

Solid basaloid adenoid cystic carcinoma (SB-AdCC) is a subtype of breast AdCC which shows more aggressive clinical behavior than other subtypes. Fine-needle aspiration (FNA) cytology is a useful diagnostic tool for breast malignancies. However, most of the diagnostic cytological characteristics of AdCC are not present in SB-AdCC and cytomorphological studies of this subtype are limited. Here, we evaluated the utility of FNA in the diagnosis of SB-AdCC of the breast. A search of the pathology archives of our institutions for FNA specimens of histologically confirmed SB-AdCC between 2012 and 2019 identified four patients with SB-AdCC of the breast. All patients were female and the average age was 60 years. Cytologically, one case was classified as malignant, two as indeterminate, and one as unsatisfactory. Smears had low to moderate cellularity. All smears showed ribbon-like material surrounding the clusters and a vertical nuclear arrangement toward the peripheral rim. Hyaline globules appeared only in one case. Cells in all cases showed an oval, angular, and spindle shape hyperchromatic nuclei with mild to severe atypia, and also dispersed naked nuclei similar to the cells of the clusters were detected in one case. In histological sections, these cytological findings were compatible with the histological findings and divergent histological differentiation was detected. Diagnosing of few cellular smears of SB-AdCC is difficult whereas the features of peripheral rim of the clusters, naked nuclei, and the divergent differentiation may be important for diagnosing SB-AdCC of the breast.