Acinic cell-like carcinoma of the breast

Breast Carcinomas Resembling Acinic Cell Carcinoma: Comprehensive Analysis of 14 Cases and Review of the Literature

Acinic cell carcinoma (AciCC) of the breast is an exceptionally rare subtype of invasive breast carcinoma, often exhibiting a triple-negative phenotype and relatively indolent behavior. Since the first case reported by Roncaroli and colleagues in 1996, no more than 60 additional cases have been described in English medical journals, usually as case reports or small case series. In this study, we presented an in-depth analysis of 14 cases of AciCC of the breast, including 4 pure AciCCs and 10 AciCCs mixed with other histologic types. We reported the clinicopathologic characteristics, histologic components, treatment modalities including response to neoadjuvant treatment in 3 patients, and outcomes. In addition, we assessed the expression of nuclear transcription factor nuclear receptor subfamily 4 group A member 3 by immunohistochemistry and gene rearrangements by fluorescence in situ hybridization, which has been implicated in AciCC of the salivary gland. All 14 cases were negative for nuclear receptor subfamily 4 group A member 3 expression, and no gene rearrangements were detected. We also conducted a thorough review of the literature to highlight advancements in understanding this rare breast cancer subtype. This study aims to enhance clinical knowledge of AciCC of the breast and contributed to growing evidence that AciCC of the breast and AciCC of the salivary glands appear to be unrelated entities, despite sharing a similar histologic appearance.

Breast acinic cell carcinoma with weak progesterone receptor expression: a case report and literature review

Rationale

Acinic cell carcinoma (AcCC) of the breast is an extremely rare malignant epithelial tumor characterized by acini cell differentiation, clinical low-grade malignancy, and a molecular triple-negative subtype.

Patient concern

A 47-year-old female presented with a 1-month history of a painless mass in her right breast.

Diagnosis

Ultrasound imaging, mammography and magnetic resonance imaging revealed a lesion, approximately 3.0cm×1.5cm in size, in the right breast, which was considered to be a malignancy. After the surgery, the AcCC of the breast was confirmed histologically.

Interventions

Right breast mastectomy and sentinel lymph node biopsy were performed. Adjuvant chemotherapy included 4 cycles of doxorubicin hydrochloride (Adriamycin) and cyclophosphamide followed by 4 cycles of docetaxel (Taxotere).

Outcomes

The patient was discharged from the hospital after surgery. There was no sign of recurrence during a 9-month follow-up period.

Lessons

Acinic cell carcinoma (AcCC) of the breast is an extremely rare malignant epithelial tumor that can be accurately diagnosed based on histopathologic morphology and immunohistochemistry. The weak positive progesterone receptor (PR) expressed in this case is extremely rare, which may provide a new research direction for the endocrine therapy of AcCC. Both AcCC and microglandular adenosis(MGA) exhibit microglandular growth, and the relationship between them remains unclear. Differentiation between them not only relies on histomorphology and pathological immunohistochemistry but also depends on clinical manifestations and other presentations. Optimal treatment of AcCC is the same as that for invasive breast cancer. The prognosis is generally good, with adjuvant therapy after surgery.

New insights into acinic cell carcinoma of the breast: clinicopathology, origin of histology, molecular features, prognosis, and treatment

Acinic cell carcinoma (AciCC) of the breast is a rare malignant epithelial neoplasm, with approximately 60 cases reported in the literature. It predominantly affects women and exhibits significant histological heterogeneity. The diagnosis of breast AciCC is primarily based on the presence of eosinophilic and/or basophilic granular cytoplasm and markers of serous acinar differentiation. Despite being considered a low-grade variant of conventional triple-negative breast cancer (TNBC), over 25% of patients with breast AciCC have adverse clinical outcomes. Additionally, in early research, microglandular adenosis (MGA) and atypical MGA were considered potential precursors for various breast cancers, including intraductal carcinoma, invasive ductal carcinoma, adenoid cystic carcinoma, metaplastic carcinoma, and AciCC. Similarly, some studies have proposed that breast AciCC should be considered a type of carcinoma developing in MGA with acinic cell differentiation rather than a distinct entity. Therefore, the pathogenesis of breast AciCC has not yet been clarified. Moreover, to the best of our knowledge, the literature has not summarized the latest prognosis and treatment of breast AciCC. In this review, we synthesized the current literature and the latest developments, aiming at exploring the clinicopathology, histological origin, molecular features, prognosis, and treatment of breast AciCC from a novel perspective.

Elucidating the nature of acinic cell carcinoma of the breast with high-grade morphology: evidence from case report

BACKGROUND

Acinic cell carcinoma (AciCC) of the breast is a rare subtype of breast cancer. It was considered a low-grade triple-negative breast cancer (TNBC) with the potential to progress or transform into a high-grade lesion because of the molecular similarities with conventional aggressive TNBC in several genetic studies. Microscopically, the coexistence of classical low-grade and high-grade triple-negative components in breast AciCC is not uncommon. However, there is a scarcity of research on the comparative histopathological and genetic aspects of both components.

CASE PRESENTATION

A 34-year-old woman with a nontender mass in the upper outer quadrant of the left breast was initially diagnosed with a malignant small round cell tumor (undifferentiated or poorly differentiated carcinoma) based on a preoperative biopsy, which was later identified as breast AciCC with a high-grade solid component. Left breast-conserving surgery with sentinel lymph node biopsy was performed. Microscopically, the breast AciCC consisted of a classical acinic component and a high-grade component. The latter demonstrated a solid sheet-like pattern characterized by large, round, pleomorphic or vesicular nuclei, prominent nucleoli, and frequent mitotic activities. Classical acinic architectures focally merged together to form solid nests and transited into high-grade areas. Remarkably, in the high-grade lesion, conventional immunochemical markers for breast AciCC, such as α1-antitrypsin (AAT), Lysozyme (LYS), Epithelial membrane antigen (EMA), S100 protein (S100), and cytokeratin (CK) were negative, whereas cell cycle protein D1 (cyclin D1) and vimentin showed diffuse expression. Next‑generation sequencing (NGS) revealed that 43.5% of variants were identical in both components. Furthermore, PAK5 mutation; copy number (CN) loss of CDH1, CHEK1, and MLH1; and CN gains of CDK6, HGF, and FOXP1 were identified in the high-grade lesion. The patient was treated with eight cycles of adjuvant chemotherapy (epirubicin combined with cyclophosphamide) and radiotherapy after surgery, and she is currently alive for 43 months with no metastases or recurrences.

CONCLUSIONS

This case demonstrates a comparative analysis of the histopathological and genetic characteristics of classical low-grade and high-grade components of AciCC within the same breast. This information may serve as a morphological and molecular basis for further investigation into the molecular mechanisms underlying high-grade lesions in breast AciCC.

Clinicopathological, immunohistochemical and molecular features of acinic cell carcinoma of the breast

Breast acinic cell carcinoma (ACC) is a rare subtype of breast cancer. Accurate diagnosis of ACC using core needle biopsy (CNB) is pivotal for the use of effective treatments and patient prognosis. In the present study, a detailed analysis of the morphological, immunohistochemical and gene mutation features of 2 cases of ACC was performed. CNB was performed prior to surgical excision. The breast ACC in the present cases exhibited overt burrowing labyrinthine networks or 'hand-holding-hand' features. The tumor cells in both of the present cases expressed cytokeratin (CK)7, S100 and CK5/6, but were negative for p63, estrogen receptor and progesterone receptor. GATA binding protein 3 was positive in case 1 but negative in case 2. Fluorescence in situ hybridization indicated no ETS variant transcription factor 6 break-apart probe detection. Next-generation sequencing results revealed the same mutation and a similar abundance in exon 27 (NM_005120.2; c.3817G>T; p.A1273S) of the mediator of RNA polymerase II transcription, subunit 12 homolog (MED12) gene in both patients. To conclude, the findings of the present study suggested that recognition of this rare 'hand-holding-hand' structure could potentially be beneficial for avoiding patient misdiagnosis. In addition, it could be suggested that a mutation in the MED12 exon 27 was associated with the formation of a burrowing labyrinthine network or 'hand-holding-hand' feature.

Primary acinic cell carcinoma of the breast: A case report and review of literature

BACKGROUND

In the current World Health Organization classification, acinic cell carcinoma (AcCC) of the breast is considered a rare histological subtype of triple-negative breast cancer. Because of the few reports in the literature, data concerning clinical outcomes are limited. Here, we report a case of AcCC of the breast in a 48-year-old woman.

CASE SUMMARY

A 48-year-old woman with a mass in her right breast came to our hospital for further diagnosis. Mammography and an ultrasound (US) scan showed a mass in the upper inner side of the right breast. She then underwent surgery to resect the mass in her right breast. Postoperative pathological examination revealed that the tumor had abundant acinar-like structures formed by tumor cells with prominent eosinophilic granules in the cytoplasm, consistent with acinar cell carcinoma. The results of immunohistochemical analysis supported the diagnosis of breast acinar cell carcinoma. Two months later, she underwent breast-conserving surgery and sentinel lymph node biopsy. The pTNM stage was T2N0M0. After surgery, the patient received 30 radiotherapy sessions. The patient was followed up for a period of one year, and no recurrence was found.

CONCLUSION

AcCC of the breast is a rare type of malignant tumor. Because it is usually asymptomatic and can be detected by imaging studies, routine breast US or mammograms are important. However, there are no characteristic diagnostic imaging findings or clinical manifestations, so immunohistochemical examination is critical for an accurate diagnosis of AcCC of the breast.

Acinic Cell Carcinoma of the Breast: A Case Report and Review of Literature

Acinic cell carcinoma (ACC) is an exceedingly rare type of triple-negative breast cancer (TNBC). We are reporting a case of a 46-year-old female patient who presented with a palpable lump in her left breast not associated with pain, pruritis, or change of skin color. An open biopsy revealed a mass of about 20 x 25 mm of fleshy, white tan with a lobular configuration and necrosis. The histopathological examination revealed cells with cytoplasmic granularity arranged in a microglandular pattern and a solid pattern, and the case was initially reported as ACC. The most remarkable feature was the presence of small and large, brightly eosinophilic cytoplasmic granules, and some cells are clear or multivacuolated, resembling lipoblasts. Cellular pleomorphism and anaplasia are very mild, and the mitotic activity was very low. The tumor showed a scant and vascularized stroma in the area of hyalinization. Small clusters of lymphoid infiltration in the stroma were seen. Histochemical stains revealed that the acinar cells in ACC contain abundant diastase-resistant, periodic acid Schiff (PAS)-positive cytoplasmic granules. Mucicarmine and Alcian blue were negative. The immunohistochemistry workup revealed that the case was positive for discovered on gastrointestinal stromal tumors-1 (DOG-1) and the positivity pattern ranged from apical membranous, cytoplasmic, and complete membranous. In addition, the tumor cells were positive for low-molecular-weight cytokeratin, carcinoembryonic antigen (CEA), and epithelial membrane antigen (EMA). The FISH workup for the ETV6-NTRK3 fusion was negative, arguing against secretory carcinoma (SC). A diagnosis of acinar cell carcinoma of the breast is very rare, and the presence of cytoplasmic granules is helpful for its diagnosis. In the absence of these granules, the diagnosis is very difficult, and other diagnoses will be put in the differential diagnosis, particularly SC, lactating adenosis, and microglandular adenosis. Immunohistochemical and histochemical stains and genetic workups will support the diagnosis of ACC.

NR4A3 Expression Is Consistently Absent in Acinic Cell Carcinomas of the Breast: A Potential Nosologic Shift

Acinic cell carcinoma (AciCC) is a tumor that is recognized in both the breast and salivary glands. Recently, the recurrent genomic rearrangement, t(4;9)(q13;q31) was identified in salivary AciCC that results in constitutive upregulation of the nuclear transcription factor NR4A3, which can be detected by immunohistochemistry. In this study, we sought to evaluate NR4A3 expression in breast AciCC using immunohistochemistry. Strong and diffuse nuclear staining was considered a positive result. Sixteen AciCCs were studied, including 8 pure AciCCs and 8 AciCCs admixed with other types (invasive carcinoma of no special type in 5 cases and metaplastic carcinoma in 3 cases). All 16 AciCCs showed negative results for NR4A3 expression. Four cases with available material were evaluated for rearrangements of the NR4A3 gene by fluorescence in situ hybridization and no rearrangements were observed. Whole-genome sequencing of 1 AciCC revealed a TP53 splice-site mutation, high levels of genomic instability, and genomic features of homologous recombination DNA repair defects; a structural variant analysis of this case did not reveal the presence of a t(4;9) rearrangement. We conclude that breast AciCCs consistently lack NR4A3 rearrangement or overexpression, unlike most of the salivary AciCCs, and that consistent with previous results, breast AciCCs are associated with genomic alterations more similar to those seen in triple-negative breast carcinomas than salivary gland AciCCs. These results suggest that unlike other salivary gland-like tumors that occur in the breast, the molecular underpinnings of the salivary gland and breast AciCCs are different and that the salivary gland and breast AciCCs likely represent distinct entities.

Acinic cell carcinoma of the breast: A comprehensive review

Acinic cell carcinoma of the breast is a rare special subtype of breast cancer in the category of salivary gland-type tumors. It is morphologically similar to acinic cell carcinomas of salivary glands and pancreas and has a triple-negative phenotype (estrogen receptor-negative, progesterone receptor-negative, and Her-2/neu negative). Its molecular genomic features are more similar to triple-negative breast cancer of no special type than to its salivary gland counterpart. However, the clinical course of the mammary acinic cell carcinoma appears to be less aggressive than the usual triple-negative breast carcinomas. This review comprehensively summarizes the current literature on the clinicopathologic, immunohistochemical, and molecular features of this rare and distinct subtype of breast cancer.

Two cases of mammary acinic cell carcinomas with microglandular structures mimicking microglandular adenosis

Acinic cell carcinoma (AcCC) of breast is a rare subtype of triple-negative breast carcinoma demonstrating a wide morphologic spectrum. In this study, we perform a detailed morphologic and immunohistochemical description of two cases of the rare entity and review the published relative literature. Histologically, the two cases both showed predominantly microglandular and solid structures overlapping with the histological features of microglandular adenosis (MGA), and one case presented spindle cell metaplastic carcinoma with chondromyxoid matrix as a minor morphologic pattern. In two cases, most of the cancer cells were positive for lysozyme and antitrypsin strongly and extensively, but negative for estrogen receptor (ER), progesterone receptor (PR), androgen receptors (AR) and human epidermal growth factor receptor 2 (HER2). The true relationship between breast AcCC and MGA or carcinoma arising in MGA(CAMGA) may remain unclear; re-excision is advised when the MGA-like content extends to the surgical margins in the setting of breast AcCC. More cases and further molecular investigations are required to elucidate the true histogenesis and give the patients appropriate treatment.

Low-risk triple-negative breast cancers: Clinico-pathological and molecular features

Triple-negative breast cancers (TNBC) comprise biologically and clinically heterogeneous diseases characterized by the lack of hormone receptors (HR) and HER2 expression. This subset of tumors accounts for 15-20% of all breast cancers and pursues an ominous clinical course. However, there is a spectrum of low-risk TNBCs with no/minimal metastatic potential, including the salivary gland-type tumors, those with extensive apocrine differentiation and/or high tumor-infiltrating lymphocytes, and small-sized, early-stage (pT1a/bN0M0) TNBCs. De-escalating the treatment in low-risk TNBC, however, is not trivial because of the substantial lack of dedicated randomized clinical trials and cancer registries. The development of new diagnostic and/or prognostic biomarkers based on clinical and molecular aspects of low-risk TNBCs would lead to improved clinical treatment. Here, we sought to provide a portrait of the clinicopathological and molecular features of low-risk TNBC, with a focus on the diagnostic challenges along with the most important biological characteristics underpinning their favorable clinical course.

Primary acinic cell carcinoma of the breast is associated with a poor outcome: A case report and literature review

Primary acinic cell carcinoma (AcCC) is a rare histological type of malignant breast cancer. AcCC was first identified as an entity in 1996, and since then 51 cases have been reported in the literature. The first early case reports and reviews suggested a relatively favourable prognosis for patients with AcCC; however, reports of AcCC recurrent disease have been more recently described in a subset of patients with high-grade disease. The present case report describes an unusual case of estrogen receptor-negative AcCC of the breast in a 59-year-old woman who did not respond to neoadjuvant chemotherapy (NACT), despite imaging revealing a large reduction in tumour volume. Furthermore, 14 months after NACT completion, the patient presented with disease progression comprising peritoneal involvement and linitis plastica. The patient started on first-line chemotherapy with carboplatin and paclitaxel combination, achieving a notable and prolonged response. After 2.5 years and while still on carboplatin and paclitaxel, the patient developed leptomeningeal carcinomatosis disease (LD) and died 6 weeks after LD presentation. The present report is the third case of AcCC in which cancer-associated death was registered. As studies on large series are lacking, further investigations are required to identify predictors of poor outcome. Notably, the prolonged response achieved to first-line chemotherapy suggested that platinum and taxane compounds may offer a potential therapeutic benefit for patients with AcCC. Moreover, the present case report highlights the importance of careful interpretation of follow-up imaging, as an apparent positive response to treatment may not always be a true representation of disease.

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.

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.

Triple negative breast cancer: special histological types and emerging therapeutic methods

Triple negative breast cancer (TNBC) is a complex and malignant breast cancer subtype that lacks expression of the estrogen receptor (ER), progesterone receptor (PR) and human epidermal growth factor receptor 2 (HER2), thereby making therapeutic targeting difficult. TNBC is generally considered to have high malignancy and poor prognosis. However, patients diagnosed with certain rare histomorphologic subtypes of TNBC have better prognosis than those diagnosed with typical triple negative breast cancer. In addition, with the discovery and development of novel treatment targets such as the androgen receptor (AR), PI3K/AKT/mTOR and AMPK signaling pathways, as well as emerging immunotherapies, the therapeutic options for TNBC are increasing. In this paper, we review the literature on various histological types of TNBC and focus on newly developed therapeutic strategies that target and potentially affect molecular pathways or emerging oncogenes, thus providing a basis for future tailored therapies focused on the mutational aspects of TNBC.

Whole-exome sequencing and RNA sequencing analyses of acinic cell carcinomas of the breast

AIMS

Acinic cell carcinoma (ACC) of the breast is a rare histological form of triple-negative breast cancer (TNBC). Despite its unique histology, targeted sequencing analysis has failed to identify recurrent genetic alterations other than those found in common forms of TNBC. Here we subjected three breast ACCs to whole-exome and RNA sequencing to determine whether they would harbour a pathognomonic genetic alteration.

METHODS AND RESULTS

DNA and RNA samples from three breast ACCs were subjected to whole-exome sequencing and RNA-sequencing, respectively. Somatic mutations, copy number alterations, mutational signatures and fusion genes were determined with state-of-the-art bioinformatics methods. Our analyses revealed TP53 hotspot mutations associated with loss of heterozygosity of the wild-type allele in two cases. Mutations affecting homologous recombination DNA repair-related genes were found in two cases, and an MLH1 pathogenic germline variant was found in one case. In addition, copy number analysis revealed the presence of a somatic BRCA1 homozygous deletion and focal amplification of 12q14.3-12q21.1, encompassing MDM2, HMGA2, FRS2, and PTPRB. No oncogenic in-frame fusion transcript was identified in the three breast ACCs analysed.

CONCLUSIONS

No pathognomonic genetic alterations were detected in the breast ACCs analysed. These tumours have somatic genetic alterations similar to those of common forms of TNBC, and may show homologous recombination deficiency or microsatellite instability. These findings provide further insights into why breast ACCs, which are usually clinically indolent, may evolve into or in parallel with high-grade TNBC.

Primary Mammary Analog Secretory Carcinoma (MASC) of the Vulva With ETV6-NTRK3 Fusion: A Case Report

Mammary analog secretory carcinoma is a primary salivary gland neoplasm with histologic, immunophenotypic, and molecular features identical to those of secretory carcinoma of the breast. Similar neoplasms have now been reported to occur in various nonmammary sites including the parotid gland, submandibular gland, sinuses, lip, skin, thyroid gland, and lung. We report, to our knowledge, the first example of a primary vulvar neoplasm with pathologic features identical to secretory carcinoma of the breast and an ETV6-NTRK3 fusion.

Primary acinic cell carcinoma of the breast: A case report with a clinicopathological and immunohistochemical study of a rare breast cancer subtype

Acinic cell carcinoma (ACC) of the breast is extremely rare subtype of triple-negative breast carcinoma and demonstrates extensive morphologic overlap with acinic cell carcinoma of the salivary gland. Herein, we report a case of acinic cell carcinoma of the breast in a 41-year old female presenting with a palpable breast mass along with significant morphological and immunohistochemical findings. Histologically, ACC showed a diffuse glandular infiltrative pattern, with small acinar or glandular structures mixed with solid nests. Both glandular and solid tumor cell populations were strongly positive for lysozyme. The immunohistochemical profile of the tumor was also similar to that of salivary gland acinic cell carcinoma. She received postoperative chemoradiation therapy and has been doing well. As studies on large series are lacking, further studies are needed to elucidate the biological characteristics of acinic cell carcinoma of the breast. In this study, we perform a detailed morphologic and immunohistochemical description of cases of this rare entity and undertake a comprehensive review of all reported cases of breast acinic cell carcinoma in the English language literature to date.

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Acinic cell carcinoma of the breast is extremely rare subtype of breast carcinoma.

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Only 16 cases of ACC of the breast have been reported since 1996.

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Immunohistochemical examination is important in making an accurate diagnosis.

Pure acinic cell carcinoma of the breast: A case report and literature review

RATIONALE

Acinic cell carcinoma (AcCC) of the breast is a rare histological type of malignant epithelial neoplasm exhibiting acinic cell differentiation.

PATIENT CONCERNS

A 52-year-old woman presented to the hospital with a palpable mass over the upper outer quadrant of the right breast.

DIAGNOSES

Physical examination revealed an irregular mass in the lateral upper quadrant of the left breast, approximately 1.5 cm in diameter. Histologically, the tumor cells were round to oval, had displaced nuclei with striking single nucleoli and basophilic cytoplasm, and contained large coarse cytoplasmic granules. They showed an infiltrating growth pattern with a combination of cystic and cribriform feature. We diagnosed the tumor as AcCC of the breast.

INTERVENTIONS

The patient was given a simple mastectomy and sentinel lymph node biopsy. After the surgery, AcCC of the breast was confirmed histologically.

OUTCOMES

The patient was symptom free 3 months after surgery.

LESSONS

AcCC of the breast is a very rare tumor, and its prognosis appears to be good. Thus, treatment followed the guidelines for invasive breast carcinoma and no further therapy was suggested by oncologists based on the tumor biology.

Acinic cell carcinoma of breast: morphologic and immunohistochemical review of a rare breast cancer subtype

Acinic cell carcinoma of breast is a rare subtype of triple-negative breast carcinoma and demonstrates extensive morphologic overlap with acinic cell carcinoma of the salivary gland. In this study, we perform a detailed morphologic and immunohistochemical description of 2 cases of this rare entity and undertake a comprehensive review of all reported cases of breast acinic cell carcinoma in the English language literature to date. One-third of reported cases of breast acinic cell carcinoma have been associated with the presence of a ductal carcinoma not otherwise specified component, which is frequently poorly differentiated. Breast acinic cell carcinoma can demonstrate focal morphologic features similar to microglandular adenosis; these areas are frequently negative for collagen IV and laminin on immunohistochemistry. The true relationship between these 2 entities remains unclear, but we advocate that microglandular adenosis-like areas at the periphery of a breast acinic cell carcinoma should be considered part of the carcinomatous process and re-excised if this process extends to the initial surgical margins.

The repertoire of somatic genetic alterations of acinic cell carcinomas of the breast: an exploratory, hypothesis-generating study

Acinic cell carcinoma (ACC) of the breast is a rare form of triple-negative (that is, oestrogen receptor-negative, progesterone receptor-negative, HER2-negative) salivary gland-type tumour displaying serous acinar differentiation. Despite its triple-negative phenotype, breast ACCs are reported to have an indolent clinical behaviour. Here, we sought to define whether ACCs have a mutational repertoire distinct from that of other triple-negative breast cancers (TNBCs). DNA was extracted from microdissected formalin-fixed, paraffin-embedded sections of tumour and normal tissue from two pure and six mixed breast ACCs. Each tumour component of the mixed cases was microdissected separately. Tumour and normal samples were subjected to targeted capture massively parallel sequencing targeting all exons of 254 genes, including genes most frequently mutated in breast cancer and related to DNA repair. Selected somatic mutations were validated by targeted amplicon resequencing and Sanger sequencing. Akin to other forms of TNBC, the most frequently mutated gene found in breast ACCs was TP53 (one pure and six mixed cases). Additional somatic mutations affecting breast cancer-related genes found in ACCs included PIK3CA, MTOR, CTNNB1, BRCA1, ERBB4, ERBB3, INPP4B, and FGFR2. Copy number alteration analysis revealed complex patterns of gains and losses similar to those of common forms of TNBCs. Of the mixed cases analysed, identical somatic mutations were found in the acinic and the high-grade non-acinic components in two out of four cases analysed, providing evidence of their clonal relatedness. In conclusion, breast ACCs display the hallmark somatic genetic alterations found in high-grade forms of TNBC, including complex patterns of gene copy number alterations and recurrent TP53 mutations. Furthermore, we provide circumstantial genetic evidence to suggest that ACCs may constitute the substrate for the development of more aggressive forms of triple-negative disease.

Are acinic cell carcinomas of the breast and salivary glands distinct diseases?

AIMS

Acinic cell carcinomas (AcCC) of the breast have been reported to constitute the breast counterpart of salivary gland AcCCs, based on the similarities of their histological and immunohistochemical features. Breast AcCC is a vanishingly rare form of triple-negative breast cancer (TNBC). Recent studies have demonstrated that in TNBCs, the two driver genes most frequently mutated are TP53 (82%) and PIK3CA (10%). We sought to define whether breast AcCCs would harbour TP53 and PIK3CA somatic mutations, and if so, whether these would be present in salivary gland AcCCs.

METHODS AND RESULTS

Sanger sequencing of the entire coding region of TP53 and of PIK3CA hotspot mutation sites of 10 breast and 20 salivary gland microdissected AcCCs revealed eight TP53 (80%) and one PIK3CA (10%) somatic mutations in breast AcCCs. No somatic mutations affecting these genes were found in the 20 salivary gland AcCCs analysed.

CONCLUSIONS

Our findings demonstrate that breast AcCCs display TP53 and PIK3CA mutations at frequencies similar to those of common types of TNBCs, whereas these genes appear not to be altered in salivary gland AcCCs, suggesting that despite their similar histological appearances, AcCCs of the breast and salivary glands probably constitute unrelated diseases.

The first case of acinic cell carcinoma of the breast within a fibroadenoma: case report

A case of acinic cell carcinoma of the breast is reported in a 26-year-old woman. She presented a lump in her right breast, that seemed to be a fibroadenoma. The open biopsy revealed a well-bordered fibroadenoma, together with a proliferation of cells characterized by serous acinar differentiation and eosinophilic cytoplasmic granules. Tumor cells stained for amylase, lysozyme, α-1-antichymotripsin, epithelial membrane antigen, S-100 protein, pan-cytokeratin, cytokeratin 7 and E-cadherin. Estrogen receptor, progesterone receptor, human epidermal growth factor receptor 2 overexpression, CD10, P63, smooth muscle actin, cytokeratin 5/6 were negative. The sentinel node was negative. 8 months after surgery she is in good clinical conditions without recurrence or metastases.

Acinic cell carcinoma of the breast: review of the literature

INTRODUCTION

The breast and salivary gland tissue share embryologic and thus pathological similarities. Acinic cell carcinoma (ACC) is a typical tumor in salivary glands, but rarely arises in breast too. We reviewed 38 cases of mammary ACC reported in literature and our case, the first ACC born within a fibroadenoma.

MATERIALS AND METHODS

Data were collected by a research for the key words acinic cell carcinoma breast on Pubmed in March 2014, including a case treated in our department. All reviewed cases were compared for clinical approach and histological pattern.

RESULTS

To date 23 articles presenting cases of ACC of the breast are reported in literature. We included in our review 38 cases previously described and one new case. The histological pattern was predominantly solid with a microglandular structure. All the tumor cells were cytologically characterized by monotonous round cells with a finely granular, weakly eosinophilic, or clearly vacuolated cytoplasm. The most of the cells were intensely stained with anti-lysozime, anti-amylase, anti-α1-chimotripsin, anti-EMA and anti-S100 protein antisera. Immunohistochemistry was also performed to point out: estrogen receptor (ER), progesterone receptor (PR), androgen receptors (AR), human epidermal growth factor receptor 2 overexpression (HER2/neu), E-cadherin (E-cad), cytokeratin-7 (CK7), gross cystic disease fluid protein 15 (GCDFP15), smooth muscle actin (SMA).

CONCLUSION

ACC of the breast is a rare tumor, showing similarities with the salivary gland counterpart, above all in terms of good prognosis, and differences from the ordinary invasive breast carcinoma. Further investigations are needed to elucidate the true histogenesis and the correct treatment.

Acinic cell carcinoma of the breast arising in microglandular adenosis

Acinic cell carcinoma is a rare breast tumour belonging to salivary gland-like tumours of the breast. They are “triple-negative” breast cancers even if their biological behaviour seems to be more favourable. Herein we present an acinic cell carcinoma arising on a background of typical and atypical microglandular adenosis in a 58-year-old woman, along with a review of the literature.

Rare breast tumors: Review of the literature

Breast cancer tumors have different morphological phenotypes and specific histopathological types with particular prognostic and clinical characteristics. The treatment of rare malignant lesions is frequently controversial due to the absence of trials to determine the optimal managements. This review describes the spectrum of rare breast tumors indicating the clinical, epidemiological and treatment characteristics.

Primary acinic cell carcinoma of the breast: a clinicopathological and immunohistochemical study

Acinic cell carcinoma of the breast is an extremely rare, malignant neoplasm characterized by widespread acinar cell-like differentiation and clinically low-grade malignancy. Herein, we report a case of acinic cell carcinoma of the breast in a 41-year-old woman. The tumor was poorly demarcated but had a firm consistency. It was removed with lumpectomy, and sentinel lymph node biopsy was performed to check for metastasis. Microscopically, the tumor showed an infiltrative growth pattern with a combination of solid, trabecular, and microglandular areas. Many of the tumor cells had abundant clear vacuolated cytoplasm containing zymogen-typed granules which resemble acinar cells of the salivary glands. The immunohistochemical profile of the tumor was also similar to that of salivary gland acinic cell carcinoma: the tumor cells were positive for amylase, lysozyme, α-1-antichymotrypsin, S-100 protein, and epithelial membrane antigen and negative for estrogen receptor, progesterone receptor, and human epidermal growth factor receptor 2. She received postoperative chemoradiation therapy and has been well for 3 years since surgery. As studies on large series are lacking, further studies are needed to elucidate the biological characteristics of acinic cell carcinoma of the breast.

Secretory carcinoma of the breast and its histopathological mimics: value of markers for differential diagnosis

AIMS

Secretory carcinoma (SC) is a rare histological type of breast cancer, and ETV6-NTRK3 gene fusion is highly specific to it. The differential diagnoses of SC include acinic cell carcinoma (ACCA) and cystic hypersecretory carcinoma (CHC), as well as invasive ductal carcinoma (IDC). For patients with these rare but distinctive histological subtypes, SC and its histopathological mimics should be differentiated from each other. However, differential markers have not yet been assessed systematically, and we aimed to identify and evaluate novel and existing markers.

METHODS AND RESULTS

We reviewed 19 cases diagnosed initially as SC using integrated diagnostic techniques, including morphology, immunohistochemistry and molecular pathology, and validated promising markers in 445 breast cancers. We reclassified 19 formerly diagnosed 'SCs' into nine SCs, three ACCAs, three CHCs, three IDCs and one microglandular adenosis. We confirmed that ETV6-NTRK3 gene rearrangement and amylase positivity are good diagnostic markers for SC and ACCA, respectively. Vacuolar staining for adipophilin, positivity for α-lactalbumin and negativity for ETV6 rearrangement are diagnostic markers for CHC.

CONCLUSIONS

In this study, we propose a panel of four markers (ETV6 rearrangement, amylase, α-lactalbumin and adipophilin) for distinguishing SC, ACCA, CHC and IDC. This simple but robust panel will serve pathologists well as a practical guide for reaching an appropriate diagnosis.

Primary acinic cell carcinoma of the breast: a case report and review of the literature

Acinic cell carcinoma (ACC) of the breast is a rare tumor that is listed in the 2003 World Health Organization (WHO) classification of tumors of the breast. Pure form ACC of the breast is even rarer. To date, only 12 cases have been reported in the English-language literature. A case of primary ACC of the breast in a 38-year-old woman is presented in this report. Histologically, the neoplastic cells are characterized by widespread acinci cell-like differentiation with a eosinophilic granular or clear cytoplasm, resembling acinic cells of the parotid gland. In addition, the neoplastic cells are positive for lysozyme, EMA, S-100, CD68 and GCDFP-15 and negative for α-anti-chymotrypsin, synaptophysin, ER, PR and Her-2/neu. This primary breast tumor was confirmed by clinical, morphological, and immunohistochemical studies. Characteristic features and differential diagnosis of this tumor were discussed in the light of pertinent literature.

First description of an acinic cell carcinoma of the breast in a BRCA1 mutation carrier: a case report

Background

Acinic cell carcinoma (ACC) is a rare malignant epithelial neoplasm characterized by the presence of malignant tubular acinar exocrine gland structures. Diagnosis is generally made in salivary glands and in the pancreas. ACC of the breast has been reported in few cases only. Carriers of inherited mutations in the BRCA1 gene are prone to the development of breast cancer, mainly invasive ductal or medullary type carcinomas. We describe for the first time a BRCA1 mutation carrier with a diagnosis of ACC of the breast.

Case presentation

The patient developed an invasive ductal carcinoma (IDC) at the age of 40 years and an ACC in the contralateral breast at 44 years. Immunohistochemical examination of the ACC revealed a triple negative status (i.e., negativity for estrogen receptor, progesterone receptor and HER2 protein) and positivity for p53. Using a combination of loss of heterozygosity (LOH) and sequencing analyses, the loss of the wild-type BRCA1 allele was detected in both the ACC and the IDC. In addition, two different somatic TP53 mutations, one in the ACC only and another one in the IDC only, were observed.

Conclusion

Both the immunohistochemical and molecular features observed in the ACC are typical of BRCA1-associated breast cancers and suggest an involvement of the patient’s germline mutation in the disease. The occurrence of rare histological types of breast cancers, including malignant phyllodes tumor, atypical medullary carcinoma and metaplastic carcinoma, in BRCA1 mutation carriers has been already reported. Our findings further broaden the spectrum of BRCA1-associated breast malignancies.

Primary acinic cell carcinoma of the breast: a case report with an immunohistochemical and ultrastructural studies

Acinic cell carcinoma (ACC) of the breast is extremely rare and is characterized by widespread acinar cell-like differentiation. We report of a 39-year-old woman presented with a palpable breast mass with significant morphological, immunohistochemical and ultrastructural findings. Histologically, ACC showed a diffuse glandular infiltrative pattern, with small acinar or glandular structures mixed with solid nests. Neoplastic cells were monotonous proliferation of cells with a granular or clear cytoplasm, resembling acinar cells of the salivary glands or Paneth cells. Both glandular and solid tumor cell populations were strongly positive for lysozyme and α-1-antitrypsin.

Paneth cell-like eosinophilic cytoplasmic granules in breast carcinoma

Prominent coarse eosinophilic cytoplasmic granules reminiscent of those in intestinal Paneth cells are rarely identified in breast carcinomas. In the literature, this phenomenon seems to be associated with acinic cell carcinoma of the breast or microglandular adenosis-related lesions. In this study, we report 3 breast carcinoma cases with such granules. Two of the cases were carcinomas arising in microglandular adenosis, one of which contained areas of acinic carcinoma-like features. The other case was a mammary carcinoma with prominent microglandular adenosis and also acinic cell carcinoma growth patterns. In the latter case, the patient had a history of neoadjuvant chemotherapy; and cells with coarse granules were found in both the pretreatment and posttreatment specimens. Although all 3 tumors were negative for HER2/neu, 2 tumors were estrogen receptor/progesterone receptor negative and one was estrogen receptor/progesterone receptor positive. Follow-up for 2 patients at 12 months and 3 years showed no evidence of disease, and the other patient died of her disease at 34 months. We provide a review of the literature and conclude that prominent coarse eosinophilic granules are a rare and nonspecific feature in breast epithelium. The clinical significance remains to be investigated, given the limited experience.

Mammary analogue secretory carcinoma of salivary glands, containing the ETV6-NTRK3 fusion gene: a hitherto undescribed salivary gland tumor entity

We present a series of 16 salivary gland tumors with histomorphologic and immunohistochemical features reminiscent of secretory carcinoma of the breast. This is a hitherto undescribed and distinctive salivary gland neoplasm, with features resembling both salivary acinic cell carcinoma (AciCC) and low-grade cystadenocarcinoma, and displaying strong similarities to breast secretory carcinoma. Microscopically, the tumors have a lobulated growth pattern and are composed of microcystic and glandular spaces with abundant eosinophilic homogenous or bubbly secretory material positive for periodic acid-Schiff, mucicarmine, MUC1, MUC4, and mammaglobin. The neoplasms also show strong vimentin, S-100 protein, and STAT5a positivity. For this tumor, we propose a designation mammary analogue secretory carcinoma of salivary glands (MASC). The 16 patients comprised 9 men and 7 women, with a mean age of 46 years (range 21 to 75). Thirteen cases occurred in the parotid gland, and one each in the minor salivary glands of the buccal mucosa, upper lip, and palate. The mean size of the tumors was 2.1 cm (range 0.7 to 5.5 cm). The duration of symptoms was recorded in 11 cases and ranged from 2 months to 30 years. Clinical follow-up was available in 13 cases, and ranged from 3 months to 10 years. Four patients suffered local recurrences. Two patients died, 1 of them owing to multiple local recurrences with extension to the temporal bone, and another owing to metastatic dissemination to cervical lymph nodes, pleura, pericardium, and lungs. We have shown a t(12;15) (p13;q25) ETV6-NTRK3 translocation in all but one case of MASC suitable for analysis. One case was not analyzable and another was not available for testing. This translocation was not found in any conventional salivary AciCC (12 cases), nor in other tumor types including pleomorphic adenoma (1 case) and low-grade cribriform cystadenocarcinoma (1 case), whereas ETV6-NTRK3 gene rearrangements were proven in all 3 tested cases of mammary secretory carcinoma. Thus, our results strongly support the concept that MASC and AciCC are different entities.

Salivary gland-type tumors of the breast: a spectrum of benign and malignant tumors including "triple negative carcinomas" of low malignant potential

Salivary gland-type neoplasms of the breast are uncommon and comprise numerous entities analogous to that more commonly seen in salivary glands. The clinicopathologic spectrum ranges from benign to malignant but there are important differences as compared with those of their salivary counterpart. In the breast, benign adenomyoepithelioma is recognized in addition to malignant one, whereas in the salivary gland a histologically similar tumor is designated as epithelial-myoepithelial carcinoma without a separate benign subgroup. Mammary adenoid cystic carcinoma is a low-grade neoplasm compared with its salivary equivalent. It is also important to appreciate that in contrast to "triple negative" conventional breast carcinomas with aggressive course, most salivary-type malignant breast neoplasms behave in a low-grade manner. Most of these tumors are capable of differentiating along both epithelial and myoepithelial lines, but the amount of each lineage-component varies from case to case, contributing to diagnostic difficulties. Well established examples of this group include pleomorphic adenoma, adenomyoepithelioma, and adenoid cystic carcinoma. Another family of salivary gland-type mammary epithelial neoplasms is devoid of myoepithelial cells. Key examples include mucoepidermoid carcinoma and acinic cell carcinoma. The number of cases of salivary gland-type mammary neoplasms in the published data is constantly increasing but some of the rarest subtypes like polymorphous low-grade adenocarcinoma and oncocytic carcinoma are "struggling" to become clinically relevant entities in line with those occurring more frequently in salivary glands.

Rare (new) entities of the breast and medullary carcinoma

Rare tumours are a heterogeneous group of conditions that encompass benign to malignant lesions both of stromal and epithelial origin. Here some of these tumours are described, in which the authors have most familiarity. An outline of medullary carcinoma is also presented.

Is acinic cell carcinoma a variant of secretory carcinoma? A FISH study using ETV6'split apart' probes

AIMS

Acinic cell carcinomas (ACCs) and secretory carcinomas (SCs) of the breast are rare, low-grade malignancies that preferentially affect young female patients. Owing to the morphological and immunohistochemical similarities between these lesions, they have been proposed to be two morphological variants of the same entity. It has been demonstrated that SCs of the breast consistently harbour the t(12;15)ETV6-NTRK3 translocation. The aim was to determine whether ACCs also harbour ETV6 gene rearrangements and are thus variants of SCs.

METHODS AND RESULTS

Using the ETV6 fluorescence in situ hybridization DNA Probe Split Signal (Dako), the presence of ETV6 rearrangements in three SCs and six ACCs was investigated. Cases were considered as harbouring an ETV6 gene rearrangement if >10% of nuclei displayed 'split apart signals' (i.e. red and green signals were separated by a distance greater than the size of two hybridization signals). Whereas the three SCs displayed ETV6 split apart signals in >10% of the neoplastic cells, no ACC showed any definite evidence of ETV6 gene rearrangement.

CONCLUSIONS

Based on the lack of ETV6 rearrangements in ACCs, our results strongly support the concept that SCs and ACCs are distinct entities and should be recorded separately in breast cancer taxonomy schemes.

[Salivary gland-like tumors of the breast]

A subset of rare benign and malignant breast tumors with and without myoepithelial differentiation are morphologically and histogenetically similar to salivary gland tumors, but may differ in incidence and clinical behavior. The clinicopathological, immunohistochemical, molecular and prognostic features of ten salivary gland-like tumor entities of the breast are discussed and compared with their respective counterparts in the salivary glands.

A hypothesis to relate salivary tumors with mammary and prostate neoplasias

Salivary, mammary and prostate glands are sex hormone-dependent organs sharing common aspects in structure, hormonal responsiveness and tumor histopathology. Salivary tumors (especially the malignant types) are not as frequent as mammary and prostate neoplasias. Hence, prognosis of some salivary tumors is not always efficient. Here, we review the oncology of salivary gland and its putative relation to breast/prostate tumors.

Salivary-type neoplasms of the breast and lung

Salivary-type tumors occur in multiple sites in the human body, likely related to a basic structural homology between exocrine glands in these different anatomic areas. This paper reviews these salivary gland tumor types in breast tissue and lung. Salivary-type tumors of both breast and lung are relatively uncommon in comparison to their salivary gland counterparts. This may be attributable in part to lack of familiarity with these tumors in extra-salivary sites, and in part to histologic overlap with other primary and metastatic tumor types. Recognition of these entities is improving as the clinical and pathologic features are better delineated, and tumors are more accurately classified. Prediction of malignant behavior is not always possible in these unusual sites. In some instances, such as adenoid cystic carcinoma, behavior is known to differ considerably from that of analogous primary salivary gland tumors and in other instances there are simply too few reported cases to allow for adequate prognostication. In fact, more recent papers discuss the need to consider a spectrum encompassing benign and malignant lesions, in both breast and lung. Of course, some entities show clear-cut evidence of malignancy with documented potential for metastasis, others show bland features and well-reported benign behavior, and the less well-defined entities reside between these two extremes. The molecular pathology of salivary gland tumors has been reasonably well investigated in that location; however; there are few molecular studies devoted to salivary-type tumors of the breast and lung. This represents a potential area for future growth in further clarifying these tumors and their behavior.

Salivary gland-like tumours of the breast: surgical and molecular pathology

Breast glands and salivary glands are tubulo-acinar exocrine glands that can manifest as tumours with similar morphological features, but that differ in incidence and clinical behaviour depending on whether they are primary in breast or salivary glands. Salivary gland-like tumours of the breast are of two types: tumours with myoepithelial differentiation and those devoid of myoepithelial differentiation. The first and more numerous group comprises a spectrum of lesions ranging from "bona fide" benign (such as benign myoepithelioma and pleomorphic adenoma), to low grade malignant (such as adenoid cystic carcinoma, low grade adenosquamous carcinoma, and adenomyoepithelioma), to high grade malignant lesions (malignant myoepithelioma). The second group comprises lesions that have only recently been recognised, such as acinic cell carcinoma, oncocytic carcinoma of the breast, and the rare mucoepidermoid carcinoma.

Primary Acinic Cell Carcinoma of the Breast

Acinic cell carcinoma (ACC) is an uncommon neoplasm of the salivary glands with low malignant potential. Even rarer is the occurrence of primary ACC of the breast, there is only one previously documented case. We now describe the second case of a primary carcinoma of the breast with morphological, ultrastructural, and immunohistochemical features consistent with an ACC. In contrast to the previous case report we report the lack of encapsulation of the tumor and a spectrum of cell types within the tumor including cells resembling well-differentiated infiltrating ductal carcinoma. Additionally we did not observe the abundant nuclear abnormalities noted in the previously published case. We report for the first time the mucicarmine-staining pattern of this tumor as well as immunohistochemistry directed against cytokeratin 7, the estrogen receptor, and the progesterone receptor.