Case Report

A Case of Metastatic Malignant BreastAdenomyoepithelioma With a Codon-61

Mutation of HRASSatomi Watanabe,1 Tomoyuki Otani,2 Tsutomu Iwasa,1 Takayuki Takahama,1

Masayuki Takeda,1 Kazuko Sakai,3 Kazuto Nishio,3 Akihiko Ito,2

Kazuhiko Nakagawa1

Clinical Practice Points

� Malignant mammary adenomyoepithelioma is a raresubtype of breast cancer, the biological characteris-tics of which are largely unknown.

� A recent study showed that codon-61 mutations of V-Ha-Ras Harvey Rat Sarcoma Viral Oncogene Homo-log (HRAS) are frequently associated with breastadenomyoepithelioma.

� We report the case of a 41-year-old premenopausalwoman with metastatic malignant

adenomyoepithelioma of the right breast harboring aQ61R mutation of HRAS.

� This is, to our knowledge, the first case of malig-nant breast adenomyoepithelioma with distantmetastases found to harbor a codon-61 mutation ofHRAS.

� Clinical sequencing might prove informative for diag-nosis of malignant mammary adenomyoepithelioma.

Clinical Breast Cancer, Vol. -, No. -, --- ª 2019 Elsevier Inc. All rights reserved.Keywords: Epithelial-myoepithelial carcinoma, HRAS mutation, Malignant adenomyoepithelioma, PIK3CA mutation, PIK3R1

mutation

IntroductionMalignant mammary adenomyoepithelioma (epithelial-myoepi-

thelial carcinoma) is a rare subtype of breast cancer characterized bydual composition of luminal and myoepithelial compartments.1,2

Malignant adenomyoepithelioma is distinguished from benignadenomyoepithelioma by the presence of nuclear atypia, increasedmitotic activity, and necrosis. Although its biological characteristicsare largely unknown, recurrent mutations of V-Ha-Ras Harvey RatSarcoma Viral Oncogene Homolog (HRAS) and of genes related tothe Phosphatidylinositol-3-Kinase and Protein Kinase B (PI3K-AKT) signaling pathway such as phosphatidylinositol 3-kinase,

1Department of Medical Oncology2Department of Pathology3Department of Genome Biology, Kindai University Faculty of Medicine, Osaka,Japan

Submitted: Mar 22, 2019; Revised: May 2, 2019; Accepted: May 7, 2019

Address for correspondence: Tsutomu Iwasa, MD, PhD, Department of MedicalOncology, Kindai University Faculty of Medicine, 377-2 Ohno-higashi, Osaka-Sayama, Osaka 589-8511, JapanFax: þ81-72-366-5000; E-mail contact: iwasa_t@med.kindai.ac.jp

1526-8209/$ - see frontmatter ª 2019 Elsevier Inc. All rights reserved.https://doi.org/10.1016/j.clbc.2019.05.001

catalytic, alpha polypeptide (PIK3CA) and phosphatidylinositol 3-kinase, p85 alpha regulatory subunit (PIK3R1) were recently shownto be associated with breast adenomyoepithelioma.3 Herein wedescribe the case of a 41-year-old woman with metastatic malignantbreast adenomyoepithelioma, for which targeted next-generationsequencing (NGS) analysis revealed the presence of a Q61R mu-tation of HRAS.

CaseRoutine screening of a 41-year-old premenopausal Japanese

woman using breast ultrasonography revealed a mass with calcifi-cation in the right breast. A core needle biopsy was performed, andthe tumor was suspected as being intraductal papilloma, which hadbeen decided to be followed-up. A year later, the patient noticed amass growing rapidly in her right breast, and a lumpectomy wasundertaken. Three months after the lumpectomy, local recurrencewas observed and mastectomy was performed. After another 9months, recurrence became apparent in the subcutaneous tissue ofthe right chest wall and lumpectomy was again performed. Becauseof the repeated recurrence, contrast-enhanced computed tomogra-phy (CT) was performed and revealed multiple lung metastases.The patient was then referred to our hospital.

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Figure 1 Chest Computed Tomography (CT) Scans (A) and (C) and Positron Emission Tomography-CT Scans With [18F]fluorodeoxyglucose (B) and (D) Performed After the Patient Was Referred to Our Hospital

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Malignant Breast Adenomyoepithelioma With HRAS Mutation

The CT and positron emission tomography-CT scans wereperformed in our hospital and showed multiple subcutaneous cysticrecurrent tumors with fluid accumulation in the right chest, bilateralaxial lymph node metastases, and multiple lung metastases, all ofwhich manifested increased [18F]fluorodeoxyglucose uptake(Figure 1). Pathological examination revealed that the primary tu-mor was a grossly well circumscribed nodular lesion, althoughmicroscopic examination revealed a histologically ragged margin.The tumor showed dual differentiation, better appreciated inimmunohistochemistry. Cytokeratin (CK) 7-positive epithelial cell-lined tubules and compressed spaces were shown, whereas anotherpopulation of cells positive for CK14, p63, CD10, and S100 sur-rounded or underlaid the CK7-positive cells (Figure 2A-C). Thecytoplasm of this second population of cells was often clear,consistent with myoepithelial differentiation, and the presence ofcollagen IV-positive basement membrane material between thesecells further supported this notion (Figure 2D). However, these cellsdid not stain with antibodies to a-smooth muscle actin or to cal-ponin, as would be expected for myoepithelial cells. Someepithelium-lined spaces were cystically dilated, and the neoplasticcells were slightly pleomorphic. The mitotic count was 8 per 10high-power fields, and areas of infarct or necrosis were present. Bothpopulations of neoplastic cells were immunohistochemically

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negative for the estrogen receptor (ER), the progesterone receptor,and HER2. A small proportion of epithelial cells was positive forER, which might have reflected entrapment of non-neoplastic ductsin the tumor. The recurrent tumors showed frank invasive growthand slightly more pronounced cytological atypia, with increasedmitotic counts. Tubular architecture was more obscure, and CK7-positive epithelial cells lined collapsed slit-like spaces and cysticallydilated spaces. The lymph node metastases also manifested biphasicdifferentiation. The pathological findings suggested a diagnosis ofmalignant adenomyoepithelioma, but the failure to detect immu-nohistochemical signals for smooth muscle antigens in any part ofthe tumor was deemed problematic for such a diagnosis.

We obtained informed consent from the patient for targeted NGSanalysis with an Ion Ampliseq Cancer Hotspot Panel v2 (Thermo-Fisher Scientific,Waltham,MA). This analysis revealed the presence ofa Q61R mutation of HRAS, which is uncommon in invasive ductalcarcinoma but was recently shown to be associated with breast ade-nomyoepithelioma.3 No other clinically relevant somatic variant wasdetected using NGS. On the basis of the combination of the histo-logical and molecular evidence, we therefore made a diagnosis of ma-lignant adenomyoepithelioma. The tumor was thus identified asmetastatic triple-negative breast cancer, classified as malignant adeno-myoepithelioma harboring the HRAS(Q61R) mutation. Genetic

Figure 2 Microscopic Findings of Malignant Adenomyoepithelioma. (A) Tubular Structures Composed of Epithelial Cells WereSurrounded by Cells That Showed Clear Cytoplasm, Suggestive of Myoepithelial Differentiation, as Well as Slight NuclearPleomorphism. Necrosis or Infarct Is Apparent at the Upper Right. Hematoxylin and Eosin Staining; OriginalMagnification 3200. (B) and (C) Immunohistochemical Staining Revealed That the Former Population of Cells Was Positivefor CK7 (B) Whereas the Latter Was Positive for CK14 (C) as Well as for p63, CD10, and S100 (Not Shown). OriginalMagnification 3200 (B) or 3100 (C). (D) Immunohistochemical Staining for Collagen IV Revealed Deposition of BasementMembrane Material Between Cells, Suggestive of Myoepithelial Differentiation. Original Magnification 3100

Satomi Watanabe et al

testing using BRACAnalysis (MyriadGenetics, Salt LakeCity, UT) didnot detect any Breast Cancer 1 mutation (BRCA1) or Breast Cancer 2(BRCA2) mutation.

The patient started first-line chemotherapy with a taxane-basedtrial regimen after providing written informed consent. After 2 cy-cles of the therapy, a CT scan revealed marked shrinkage of themultiple lung metastases, but the subcutaneous tumors had slightlyincreased in size. The response to the treatment was evaluated asstable disease according to Response Evaluation Criteria in SolidTumors version 1.1 (RECIST). The patient completed 4 cycles oftreatment, after which another CT scan revealed progression of thesubcutaneous recurrent tumors, which was evaluated as progressivedisease (RECIST). Palliative radiation therapy (40 Gy in 16 frac-tions) was administered for the subcutaneous tumors and resulted ina partial tumor reduction. Combination therapy with adriamycin(40 mg/m2) and cyclophosphamide (500 mg/m2) is planned as asecond-line treatment.

DiscussionWe presented a patient diagnosed with metastatic malignant

adenomyoepithelioma of the breast for which NGS analysis revealedthe presence of the Q61R mutation of HRAS. Malignant adeno-myoepithelioma is a rare subtype of breast cancer that is classifiedunder “epithelial-myoepithelial tumors” according to the fourth

edition of the World Health Organization Classification of Tumorsof the Breast.4 Indeed, little is known about malignant adeno-myoepithelioma because of its rarity.

Standard therapy for breast cancer according to its status forhormone receptors and HER2 is applied for malignant adeno-myoepithelioma, but its response to chemotherapy is not known.A case of malignant adenomyoepithelioma was reported torespond well to multiple chemotherapy regimens includingtaxane-based chemotherapy, anthracycline, and eribulin.5 Anothercase was reported to respond to imatinib, which is not routinelyadministered for breast cancer.6 In the present case, taxane-basedtherapy did not result in a durable response and tumor progres-sion was aggressive. However, radiotherapy induced regression ofthe subcutaneous tumors. Further studies are thus warranted toelucidate the best treatment regimen for malignantadenomyoepithelioma.

V-Ha-Ras Harvey Rat Sarcoma Viral Oncogene Homolog mu-tations are rare in breast cancer, being present in 0.62% of all breasttumors according to the Catalogue Of Somatic Mutations InCancer v87 database (https://cancer.sanger.ac.uk/cosmic).7 A recentstudy of 43 cases of mammary adenomyoepithelioma includingsome malignant cases identified recurrent mutations affectingcodon-61 of HRAS and genes related to the PI3K-AKT signalingpathway.3 All of the cases with an HRASmutation at codon 61 (n ¼

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Malignant Breast Adenomyoepithelioma With HRAS Mutation

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8) were ER-negative and had a concomitant mutation in PIK3CA orPIK3R1. Mutations of HRAS were associated with aggressive clinicalfeatures and lymph node metastasis. Another case of early-stagebreast cancer diagnosed as malignant adenomyoepitheliomaharboring HRAS and PIK3CA mutations was also recently reported,but the HRAS mutation in this instance was G12D.8 Our presentstudy revealed a codon-61 mutation of HRAS in mammary malig-nant adenomyoepithelioma with distant metastases. No mutationwas detected in PIK3CA, but the possibility of PIK3R1 mutationpositivity remains because this gene was not included in the NGSpanel used in our analysis.

Because HRAS mutation is uncommon in breast cancer andadenomyoepithelioma often presents with HRAS mutation as dis-cussed previously, the analysis of HRAS mutation would support thediagnosis of malignant adenomyoepithelioma.

ConclusionTo our knowledge, our study is the first to report a case of

malignant mammary adenomyoepithelioma with distant metastasesharboring a codon-61 mutation of HRAS. Because malignant ade-nomyoepithelioma is a rare histological subtype of breast cancer, itsdiagnosis might cause hesitation. However, the additional infor-mation provided by NGS analysis regarding the mutational acti-vation of HRAS in the present case strengthened the basis for such adiagnosis. Our report thus supports the notion that mutationalanalysis of HRAS might help in the diagnosis of malignant adeno-myoepithelioma. Further study is required to clarify the relation

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between codon-61 mutations of HRAS and the pathogenesis ofmalignant adenomyoepithelioma.

AcknowledgmentsThe authors thank Ai Yukumoto and Mami Kitano of Kindai

University for technical support. This work was supported by the 7-University Joint Project of Training Plan for OncologyProfessionals.

DisclosureThe authors have stated that they have no conflicts of interest.

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4. Tan PH, Ellis IO. Myoepithelial and epithelial-myoepithelial, mesenchymal andfibroepithelial breast lesions: updates from the WHO Classification of Tumours ofthe Breast 2012. J Clin Pathol 2013; 66:465-70.

5. Lee S, Oh SY, Kim SH, et al. Malignant adenomyoepithelioma of the breast andresponsiveness to eribulin. J Breast Cancer 2015; 18:400-3.

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