Mammary mucinous cystadenocarcinoma with long-term follow-up: molecular information and literature review

Genomic and clinical‑pathological features of mucinous cystadenocarcinoma of the breast with HER2 amplification: A case report

Mucinous cystadenocarcinoma (MCA) of the breast is a rare, invasive carcinoma that resembles pancreatobiliary or ovarian MCA in terms of histological appearance. Most cases of MCA of the breast are negative for the estrogen receptor, progesterone receptor and ERBB2 (HER2). To the best of our knowledge, only five reports of HER2-positive MCA cases have been reported in the English language, and no reports focusing on the molecular characteristics of HER2-positive MCAs have been published. In the present study, a rare case of a 64-year-old woman with HER2-positive MCA who underwent long-term follow-up without recurrence or distant metastasis is reported. In addition, a detailed analysis of the genomic characteristics of the tumor is provided.

Mutational analysis and protein expression of PI3K/AKT pathway in four mucinous cystadenocarcinoma of the breast

INTRODUCTION

Primary mucinous cystadenocarcinoma of the breast (BMCA) is a rare neoplasm with few reports in the literature. Its molecular characteristics, prognosis, and treatment protocols are not well understood, and there is a lack of consensus concerning the optimal management of this condition.

METHODS

Four cases of clinical and pathological data were collected from 2018 to 2024. Next generation sequencing with a 654 cancer-associated gene panel was utilized to detect gene mutations. Immunohistochemistry was carried out to evaluate protein expression levels.

RESULTS

Firstly, we combined clinical imaging examinations and IHC to exclude the possibility of metastasis from ovarian or pancreatic origins. BMCA was composed of cystically dilated ducts lined by tall columnar mucin-containing epithelium. The morphological spectrum of MCA varied from MCA alone to MCA combined with carcinoma in situ (CIS) to MCA associated with invasive ductal carcinoma (IDC). ER/PR/HER2 and CK20 were all negative, while CK7 and GATA3 were positive by IHC in four cases. Although the prognosis of the other three patients was favorable during the follow-up periods of 13, 10, and 3 months, respectively, case 2# experienced a recurrence of the primary focus after 42 months. No lymphatic metastasis was identified in cases 1-4#. In addition, next-generation sequencing (NGS) identified 17 mutated genes and 25 mutation sites in four cases. TP53, PIK3CA, AKT, PTEN, and RB1 were the highest frequency mutated genes. Given that AKT mutations typically refer to AKT1(E17K) rather than AKT2 or AKT3, AKT protein expression was detected only in Case 2# (AKT1, E17K). PTEN protein was expressed in case 4# (corresponded to missense mutation), loss of PTEN expression were corresponding with splicing mutation in case1#. In brief, AKT and PTEN protein expression could be corresponded to gene mutation in a certain extent. However, PIK3CA protein expression was positive in Case 2# but negative in Case 1#, which did not fully accordance with the NGS-detected missense mutations. No associated germline variations were detected. Additionally, neither PDL-1 expression nor microsatellite instability-high (MSI-H) status was identified.

CONCLUSION

The tumorigenesis and development of BMCA may be regulated to the PI3K/AKT pathway. Consequently, a comprehensive genetic analysis of more cases could elucidate the molecular mechanisms underlying this rare tumor.

Mucinous Cystadenocarcinomas of the Breast Exhibit Heterogeneous Genomic Profile as Triple Negative Breast Cancer, Harbor Alterations in PIK3CA, PTEN, AKT1, and GNAS Genes, and May Not Be Indolent

Mucinous cystadenocarcinoma of the breast is an exceedingly rare entity with less than 40 tumors reported to date. It is classified as a special subtype of breast carcinoma which exhibits low-grade indolent behavior despite having a triple-negative phenotype. Awareness of this rare tumor is essential to avoid misinterpreting it as a routine mucinous (colloid) carcinoma of the breast or metastasis from a nonmammary mucinous carcinoma. Though the clinical, histological, and immunohistochemical features of breast mucinous cystadenocarcinoma have been described thoroughly, data on molecular features remains scarce. Herein, we present 3 patients with mucinous cystadenocarcinoma, highlighting the molecular features in 2 patients and discussing the literature in this regard. Additionally, we report that these tumors have the potential for short-term recurrence despite complete surgical excision, and they therefore should probably be treated as any other triple-negative breast cancer (TNBC) with careful consideration of other factors such as patient's age, tumor size, nodal stage, and tumor grade. Review of the literature on this rare tumor together with findings from the current report suggests that MCAs at the molecular level are similar to TNBC, with frequent recurring variants in PI3K pathway genes, including PIK3CA, PTEN, and AKT1 genes. We report here for the first time the presence of GNAS variants in mucinous cystadenocarcinoma. This information could be useful to offer targeted treatment against PIK3CA and AKT1 in patients with this rare tumor.

Primary mucinous cystadenocarcinoma of the breast: A case report and literature review

Mucinous cystadenocarcinoma (MCA) is a rare breast cancer. The present study reports a case of primary MCA of the breast with a comprehensive evaluation of this rare tumour. A 51-year-old woman sought medical attention for a mass in the left breast. A core needle biopsy revealed an infiltrating adenocarcinoma with mucus secretion and papillary formation. The macroscopic appearance was of a greyish-white, tough and well-circumscribed solid mass, without a notable cyst. Microscopically, the tumour consisted of ducts and cysts of varying sizes. Varying degrees of branching papillary structures were observed in the lumen and cyst cavities. The tumour cells were highly columnar in shape, with high-grade nuclei arranged in a single-layer. Immunohistochemistry revealed that the tumour was a basal-like triple-negative breast cancer with a high proliferation index and tumour protein p53 diffuse strong expression. Mutations in breast cancer 1-associated RING domain 1 (BARD1), kinase domain containing receptor (KDR), mucin-6 (MUC6), tumour protein 53 (TP53) and breast cancer 1-interacting protein C-terminal helicase 1 (BRIP1) were identified using DNA analysis. The patient was followed up for 26 months and showed no signs of recurrence or metastasis. In conclusion, the current study presents a case of MCA of breast accompanied by mutations in the BARD1, KDR, MUC6, TP53 and BRIP1 genes, with no recurrence after a 26-month follow-up. Combining this case with a review of the literature helps us to better understand the clinicopathological and genetic characteristics of MCA, and guide treatment.

Primary Mucinous Cystadenocarcinoma of the Breast: Clinicopathological Analysis of a Case and Difficulties Encountered in a Biopsy

Background. With <40 case reports published in the English literature, mucinous cystadenocarcinoma of the breast is quite rare compared to its counterparts in the ovary, pancreas, and appendix. The purpose of this case report is to enrich scientific data by sharing the clinicopathological features of this new and extremely rare entity and present possible difficulties encountered in the biopsy materials. Case Report. A 34-year-old female patient presented with the complaint of white discharge from her left nipple lasting 8 months. Physical and radiological examination of the patient revealed a mass in the lower quadrant of the left breast and tru-cut biopsy was performed. The diagnosis of invasive breast carcinoma of no special type was reported. After neoadjuvant chemotherapy, left subcutaneous mastectomy and left sentinel lymph node biopsy were performed. Microscopic evaluation of the mastectomy material revealed a tumor consisting of stratified columnar cells with basally located nuclei and intracytoplasmic mucin, showing papillary structures and tufting toward the lumen. Peripheral myoepithelial cells were not identified with p63 and calponin immunohistochemistry. The diagnosis of mucinous cystadenocarcinoma was given through histomorphological and immunohistochemical evaluations. Conclusion. Clarifying unknown points about this rare malignancy of the breast and understanding the tumor biology is possible through evaluation of case reports. For this purpose, our case of primary mucinous cystadenocarcinoma is presented and its clinicopathological features are briefly discussed.

HER2-positive mucinous cystadenocarcinoma of the breast coexisting with invasive lobular carcinoma: A case report and review of the literature

Primary mucinous cystadenocarcinoma (MCA) of the breast is a rare variant of breast carcinoma. A 68-year-old female patient presented to the general surgery clinic with pain and swelling in the right breast. A mass was detected in the upper outer quadrant, and a fine-needle aspiration biopsy was performed. The May-Grünwald Giemsa stained slides showed aggregates of mucin-rich pleomorphic cells with large nuclei in a mucinous background containing discohesive single cells. The Papanicolaou stain revealed a papillary structure composed of malignant epithelial cells in a necrotic background. A modified radical mastectomy was performed, and upon gross examination, two tumors were discovered in the central and upper outer quadrants. The first tumor, located centrally, was identified as invasive lobular breast carcinoma. The second tumor was an MCA with cytokeratin 7(+) and cytokeratin 20(-), and was determined to be the primary MCA of the breast based on clinical and radiological information. Immunohistochemistry revealed that the tumor cells were negative for estrogen receptor and progesterone receptor, and HER2 was 2+. Fluorescence in situ hybridization analysis detected HER2 gene amplification. During the 72-month follow-up, there were no findings compatible with recurrence or new metastasis. Although primary MCA is rare, it causes differential diagnosis problems and has different biological behaviors.

Special Types of Breast Cancer: Clinical Behavior and Radiological Appearance

Breast cancer is a complex disease that includes entities with different characteristics, behaviors, and responses to treatment. Breast cancers are categorized into subgroups based on histological type and grade, and these subgroups affect clinical presentation and oncological outcomes. The subgroup of "special types" encompasses all those breast cancers with insufficient features to belong to the subgroup "invasive ductal carcinoma not otherwise specified". These cancers account for around 25% of all cases, some of them having a relatively good prognosis despite high histological grade. The purpose of this paper is to review and illustrate the radiological appearance of each special type, highlighting insights and pitfalls to guide breast radiologists in their routine work.

Primary Mucinous Cystadenocarcinoma of the Breast Intermixed with Pleomorphic Invasive Lobular Carcinoma: The First Report of This Rare Association

Primary mucinous cystadenocarcinoma (MCA) is a rare breast carcinoma subtype showing overlapping histopathological features with mucinous cystadenocarcinoma of the ovary and pancreas. Current literature data suggest a favorable prognosis of breast MCAs despite its immunoprofile usually revealing lack of expression of estrogen receptor, progesterone receptor and HER-2 and high Ki67. As far as we know, only 36 cases have been reported in the literature to date. Its ambiguous morpho-phenotypic profile makes histological diagnosis very challenging. It must be distinguished from typical mucin-producing breast carcinomas and, above all, metastases from the same histotype in other sites (ovary, pancreas, appendix). Herein, we report the case of a primary breast MCA occurring in a 41-year-old female with peculiar histological features.