Molecular Classification of Breast Cancer

Breast carcinomas classified based on traditional morphologic assessment provide useful prognostic information. Although morphology is still the gold standard of classification, recent advances in molecular technologies have enabled the classification of these tumors into four distinct subtypes based on its intrinsic molecular profile that provide both predictive and prognostic information. This article describes the association between the different molecular subtypes with the histologic subtypes of breast cancer and illustrates how these subtypes may affect the appearance of tumors on imaging studies.

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.

Adenoid Cystic Carcinoma, Solid-Basaloid Subtype of the Breast: A Case Report

We present a rare tumor of adenoid cystic carcinoma, solid-basaloid subtype of the breast. Solid-basaloid adenoid cystic carcinoma may have a worse prognosis than classical adenoid cystic carcinoma. A 70-year-old woman presented with a mass in her left breast. Malignancy was suspected on imaging and confirmed via core needle biopsy. Left breast partial mastectomy and sentinel lymph node biopsy were performed. Histologically, the tumor was composed of basaloid cells with hyperchromatic nuclei and frequent mitotic figures, as are small-cell neuroendocrine carcinomas. Immunohistochemical analysis of the tumor cells showed high expression of KIT and CD10 and focal expression of keratin 7. Synaptophysin, chromogranin A, estrogen receptor, progesterone receptor, and human epidermal growth factor receptor 2 were not expressed. This patient should be followed up carefully for distant metastases and recurrences.

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.

Breast adenoid cystic carcinoma: a report of seven cases and literature review

Background

Primary adenoid cystic carcinoma (ACC) of breast is rarely seen clinically. It is a special subtype of triple-negative breast cancer characterized by low expression of Ki-67, low malignant potential, slow progression and favorable prognosis. To date, treatment for this disease is controversial and no consensus is reached. We analyzed clinical manifestations and pathological characteristics of seven primary breast ACC cases and reported in combination with literature review to promote understanding, diagnosis and treatment of this disease.

Case presentation

We collected seven breast ACC cases pathologically diagnosed and treated in Department of breast surgery of the First Affiliated Hospital of China Medical University from January 2015 to December 2018. We organized and summarized the clinical, imaging, pathological and prognostic information and performed statistical analysis. The median age was 60 years (ranging from 54 to 64 years). Tumors of all patients were detected by immunohistochemistry. Molecular types were mostly triple negative (4/7), and Ki-67 expression was low (5/7). Lymph node metastases were absent in all patients received axillary lymph node surgery. Median follow-up time was 39 months (ranging from 25 to 68 months). There was no occurrence of relapse, distant metastasis or death.

Conclusion

Breast ACC is accompanied with favorable diagnosis, which is different from typical triple-negative breast cancer. Accurate diagnosis of ACC is particularly important.

Special Histologic Type and Rare Breast Tumors - Diagnostic Review and Clinico-Pathological Implications

Breast cancer is the most common malignant tumor in females. While most carcinomas are categorized as invasive carcinoma, no special type (NST), a diverse group of tumors with distinct pathologic and clinical features is also recognized, ranging in incidence from relatively more common to rare. So-called "special histologic type" tumors display more than 90% of a specific, distinctive histologic pattern, while a spectrum of tumors more often encountered in the salivary gland may also arise in the breast. Metaplastic carcinomas can present diagnostic challenges. Some uncommon tumors harbor pathognomonic genetic alterations. This article provides an overview of the key diagnostic points and differential diagnoses for this group of disparate lesions, as well as the salient clinical characteristics of each entity.

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.

Adenoid cystic carcinoma of the breast and intraoperative electron radiotherapy: single case report and review of literature

Adenoid cystic carcinoma (ACC) of the breast is a very rare neoplasm. It presents a triple-negative phenotype in most cases, but its prognosis is generally considered to be better than other breast cancers with the same immunohistochemical pattern. Due to its controversial features, no data are available in the literature regarding a consensus approach for ACC treatment, especially for subtypes with worse prognosis like solid basaloid ACC. We present for the first time a rare case of ACC with multifocal presentation treated with breast-conservative surgery and intraoperative electron radiotherapy, thus supporting this treatment of ACC in selected patients like young women affected by the solid basaloid variant who commonly present a worse prognosis. In this case, no local or systemic recurrence was detected after 30 months of follow-up.

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.

Triple-negative breast carcinomas of low malignant potential: review on diagnostic criteria and differential diagnoses

Triple-negative breast carcinomas constitute a wide spectrum of lesions, mostly being highly aggressive. Nevertheless, some special histologic subtypes can have low malignant potential. The purpose of the present paper is to review diagnostic criteria and prognostic parameters of breast neoplasms of special histotypes. Specifically, adenoid cystic carcinoma, adenomyoepithelioma, acinic cell carcinoma, mucoepidermoid carcinoma, tall cell carcinoma with reverse polarity, and secretory carcinoma will be discussed. For each tumour, definition and morphological and molecular features, together with prognostic parameters, will be presented. Paradigmatic cases will be illustrated.

Diagnosis of metastatic adenoid cystic carcinoma of the breast on pleural fluid cytology in a 60-year-old male

Adenoid cystic carcinoma (AdCC) is a rare triple-negative breast cancer with a favorable prognosis, although cases of distant metastases have been reported. Less than 10 cases of AdCC of the breast in males have been reported. We report a unique presentation of pleural fluid metastasis diagnosed by cytologic evaluation of pleural fluid in a 60-year-old male patient with AdCC of the breast. Careful surveillance and cytologic evaluation of effusion specimens can detect metastases with the aid of cellblock preparations and immunohistochemical stains.

[Adenoid cystic carcinoma of the breast, 22 years of experience]

INTRODUCTION

Adenoid cystic carcinoma (ACC) is an uncommon neoplasm in the breast (less than 0.1%). ACC is typically triple negative with a favourable prognosis. Its low frequency and indolent course cause difficulties in the agreement of the evaluation and therapeutic consensus, as well as the use of the sentinel node excision in these carcinomas.

OBJECTIVE

Our goal is to provide a new series of cases from the Complejo Hospitalario de Navarra, through retrospective review over a period of 22 years.

MATERIAL AND METHODS

Every case of breast ACC diagnosed between 1998-2020 is reviewed. We analyze the clinical and pathological characteristics, and compare them with the literature.

RESULTS

We identified twelve cases of ACC, from a total of 18,241 patients diagnosed with breast carcinoma, with an average tumor size of 23.8mm and mean of 63.5 years. All of them were in a stage I-II at diagnosis. One case presented a lymph node micrometastases. One of them presented local recurrences and one case presented metastases 5 months after diagnosis (93.5 months of mean follow-up). According to Nottingham Histological Score, eight cases had a grade 1, two grade 2 and two grade 3. According to the classification of Ro et al., three were grade 1, four grade 2 and five grade 3. One case was ER positive (10%). No case presents positivity for BRAF-V600E in immunohistochemistry.

CONCLUSION

The management and prognosis ACC of breast, within benignity, remains uncertain, with more studies being needed to understand the clinical evolution and perform adequate therapeutic management.

Concurrent breast adenoid cystic carcinoma and primary squamous cell carcinoma: report of a rare case with single institutional case reviews

Background

Adenoid cystic carcinoma and primary squamous cell carcinoma are both rare breast neoplasms, which possess drastically different morphological and molecular features as well as distinguishing clinical behaviors and prognosis.

Case presentation

In this report, we described a rare case in which concurrent adenoid cystic carcinoma and keratinizing squamous cell carcinoma were diagnosed in contralateral breasts in an 85 year-old female patient. The patient had a history of adenoid cystic carcinoma diagnosed 11 years ago, which was treated by partial mastectomy followed by whole breast radiation. The recurrent carcinoma on the same side of the breast was small in size but appeared to involve an intraductal papilloma. Also, a newly occurred large cystic mass was identified on the contralateral breast, which histologically presented as a keratinizing squamous cell carcinoma with no glandular differentiation. No in situ or invasive carcinoma was identified in the overlying skin of the lesion, and no malignancy in a second site was found by PET-CT. Therefore, this lesion was mostly likely a primary squamous cell carcinoma of the breast.

Conclusion

The concurrence of two such rare neoplasms was likely an incidental finding or was therapy-related. However, more mechanistic studies are needed in order to understand whether predisposing genetic alterations exist in this rare case. Besides, cases of both breast adenoid cystic carcinoma and carcinoma with predominant squamous differentiation diagnosed in our institution were reviewed, which help to better characterize their clinicopathological features.

Metastatic Basal Cell Carcinoma of the Skin: A Comprehensive Literature Review, Including Advances in Molecular Therapeutics

Basal cell carcinoma (BCC) of the skin is the most common type of malignant human tumor. In Europe, the incidence of BCC ranges from 44.6 to 128 cases per 100,000 inhabitants annually, whereas in the United States, the yearly incidence rate ranges between 500 and 1500. The global incidence has been calculated to be as high as 10 million cases of BCC per year. There are 2 main clinical patterns of BCC-the familial BCC in basal cell nevus syndrome and sporadic BCC. The etiology of cutaneous BCC is usually the result of the interaction between solar ultraviolet radiation and genetic factors. Somatic or germline mutations in the effector components of the hedgehog signaling pathway (ie, PTCH1, PTCH2, SMO or SUFU genes) are responsible for ∼90% of the cases of both sporadic and familial BCC, all causing a constitutive activation of the hedgehog pathway. Cutaneous BCC very rarely metastasizes, and diagnosis in metastatic sites can be very difficult. Metastatic BCC has weakly effective therapeutic options with a poor prognosis until few years ago. In 2012, small-molecule therapies, involving inactivation of the hedgehog signaling pathway, and capable of reducing tumor growth and progression have been introduced into clinical practice for advanced (locally advanced or metastatic) BCC. We performed a comprehensive literature review on metastatic BCC and found at least 915 cases reported to date. In addition, we extensively discussed the differential diagnosis of metastatic BCC, and outlined the advances in clinical therapeutics involving these small molecules.

Pathology of triple negative breast cancer

Triple negative breast cancer (TNBC) is a subtype of breast tumor lacking hormone receptors expression and HER2 gene amplification and represents 24 % of newly diagnosed breast neoplasms. In this review, pathological aspects of triple-negative breast cancer are illustrated, with particular attention to the seminal studies that defined this subtype of breast cancer by a molecular point of view. This paper also focuses on practical issues raised in clinical routine by the introduction of genetic expression breast cancer profiling and the innovative prognostic and predictive impact on triple-negative breast cancer pathology. Moreover, histopathological aspects of triple-negative neoplasms are also mentioned, underlying the importance of histologic diagnosis of particular cancer subtypes with decisive impact on clinical outcome. Importantly, focus on new therapeutic frontier represented by immunotherapy is illustrated, with particular mention of immune checkpoint inhibitors introduction in TNBC therapy and their impact on future treatments.

Solid-type adenoid cystic carcinoma of the breast, a distinct molecular entity enriched in NOTCH and CREBBP mutations

Adenoid cystic carcinoma (ACC) of the breast with a predominant solid pattern is difficult to diagnose with certainty and differentiate from more common triple-negative breast cancers (TNBCs) of basal-phenotype. To better characterize solid ACC, we performed a clinical, morphological, immunohistochemical, and molecular comparative analysis of 33 ACCs of the breast comprising 17 solid variant ACCs and 16 conventional ACCs. Solid ACCs displayed basaloid morphology with an exclusive or predominant epithelial cell population associated with decreased myoepithelial differentiation, while demonstrating MYB protein overexpression similar to the more common type of ACC. Strong and diffuse MYB expression by immunochemistry was observed in 14/17 (82%) of solid ACCs while MYB rearrangements were detected by break apart fluorescence in situ hybridization (FISH) in only 3/16 (19%) of solid ACCs. Conversely, weak MYB immunohistochemical expression was observed in only 7/204 (3%) of TNBC. Solid ACCs displayed a transcriptomic profile distinct from conventional ACCs with 549 genes showing a highly significant differential expression between conventional and solid ACC [false discovery rate (FDR) < 0.01; log2FC > |1|]. EnrichR and Kegg Pathway analyses identified PI3K-Akt and focal adhesion signaling pathways as significantly overexpressed in conventional ACCs compared with solid ACCs which significantly overexpressed the nitrogen metabolism pathway. CREBBP mutations and NOTCH activating gene mutations were only present in solid ACCs, concerning 5/16 (31%) of cases for each gene. Tumors with NOTCH activating mutations displayed a strong diffuse nuclear NICD1 staining, an established marker of Notch pathway activation. Solid ACCs also differed from basal-type TNBC, with fewer TP53 mutations and a more stable genomic profile on array comparative genomic hybridization (CGH). In summary, solid-type ACC of the breast is a distinct molecular entity within the ACC family and is different from common basal-type TNBC. MYB is a diagnostically useful biomarker of solid ACC and NOTCH could be a novel potential therapeutic target in 30% of cases.

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

Mammary adenoid cystic carcinoma (ACC) is a rare subtype of breast cancer with a favorable prognosis. Here we report on predictors of outcome based on a detailed morphologic review and analysis of 108 mammary ACC. Sixty-four tumors (59.2%) were pure conventional ACC, 23 (21.3%) were pure basaloid ACC. Follow-up was available for 87 patients (median: 51 mo). Eighteen patients (20.7%) developed recurrence: 7 (8%) had local recurrence and 14 (16%) had distant metastasis. Two patients died of disease, 1 died of an unrelated cause, 14 were alive with disease (including 8 in palliative care), and 70 (80.5%) were alive with no evidence of disease. Of 90 patients with known lymph node (LN) status 9 (10%) had nodal involvement (all with basaloid ACC). Distant metastases in patients with predominantly basaloid ACC compared with pure conventional ACC were more common (40% vs. 7.7%) and occurred earlier (22 vs. 84 mo). The following factors were found to be predictive of recurrence-free survival: positive margin, Nottingham grade, neovascularization, basaloid component, perineural invasion, lymphovascular invasion, >30% solid growth, necrosis and LN involvement; the first 3 remained statistically significant on multivariate analysis. Factors predictive of distant disease-free survival were neovascularization, Nottingham grade, lymphovascular invasion, solid component >50%, LN involvement, basaloid component >50%, tumor necrosis, perineural invasion, and final margin. Only neovascularization remained statistically significant on multivariate analysis. Basaloid ACC is an aggressive variant of mammary ACC with more frequent nodal involvement and higher incidence of distant spread. LN staging should be performed for all mammary basaloid ACC.

Adenoid cystic carcinoma of the breast, 20 years of experience in a single center with review of literature

BACKGROUND

Adenoid cystic carcinoma (ACC) of the breast is a rare type of breast cancer, which presents inconsistencies in the optimal management strategy.

METHODS

A retrospective review of prospectively collected data, spanning the last 20 years, was performed using the cancer registry database at our institution.

RESULTS

Six patients were diagnosed with ACC of the breast, out of 5,813 total patients diagnosed with breast cancer (0.1%). Our identified patients had a median age of 66, all with the early stage cancer (Stage I/II). The average size of the breast lesion was 1.62 cm, and nodal status was negative for all cases. All patients had resection as primary therapy (partial or total mastectomy), with one patient also undergoing external beam radiation and tamoxifen hormonal therapy. Median follow-up was 85 months, with all patients being disease-free at last follow-up.

CONCLUSIONS

ACC of the breast has an indolent course, despite triple negative status. Our study suggests that radiation may not be warranted and confirms the rarity of axillary node metastases, indicating that sentinel node excision may also not be necessary. Ultimately, the hope is that our findings along with the reviewed literature will aid in determining the most appropriate options for management of ACC of the breast.

36 cases adenoid cystic carcinoma of the breast in China: Comparison with matched grade one invasive ductal carcinoma-not otherwise specified

OBJECTIVE

The aim of this study was to investigate the clinicopathological characteristic of adenoid cystic carcinoma (ACC).

MATERIALS AND METHODS

The clininopathological features, along with relapse free survival(RFS) and overall survival(OS) of 36 patients with ACC were retrospectively investigated and compared with those of 108 grade 1 invasive ductal carcinoma not-otherwise-specified (G1-IDC-NOS) patients.

RESULTS

Most cases of ACC were ER, PR and HER-2 negative which was classified as triple-negative subtype. Five cases were concomitant with other pathological types of cancer. Axillary lymph node dissection(ALND) was performed in 31 patients and 2 of them with lymph nodes metastasis. Two patients died of lung metastases at 46 and 116 months after the surgery respectively. Compared with G1-IDC-NOS, ACC showed lower Ki-67 index, less lymph nodes metastasis, lower P53 expression, and higher proportion in location of upper outer quadrant of breast. There was no difference of OS and RFS between ACC and G1-IDC-NOS.

CONCLUSIONS

ACC of the breast was a rare disease with a good prognosis although most of them were classified as triple-negative subtype. And the value of axillary node dissection and adjuvant therapy needs to be further investigated.