Breast carcinomas of low malignant potential

Frank Invasion in Tall Cell Carcinoma With Reversed Polarity of the Breast: Report of Two Cases

Tall cell carcinoma with reversed polarity (TCCRP) is a rare neoplasm of the breast composed of columnar tumor cells arranged in solid and solid-papillary nests with evidence of apical nuclear polarity. No frank invasion is evident despite the lack of a myoepithelial cell layer throughout the tumor. TCCRP has a triple-negative or hormone receptor-low immunophenotype. Recurrent IDH2 R172 hotspot mutation coexisting with genetic alterations in the PI3K pathway characterizes this tumor. Here, we report on 2 postmenopausal patients with TCCRP with frank stromal invasion. IDH2 R172 mutations were detected in both tumors by immunohistochemistry. Targeted sequencing of case 2 demonstrated the presence of IDH2 R172T and RTEL1 E839K mutations. Both patients underwent breast conservation surgery, radiation therapy, and adjuvant endocrine therapy with anastrozole and demonstrated no evidence of disease at 65 and 25 months, respectively. This study suggests that TCCRP may give rise to frank invasive carcinoma, the prognostic significance of which is yet unknown.

Low-Grade Adenosquamous Carcinoma of the Breast: A Single-Center Retrospective Study and a Systematic Literature Review

(1) Low-grade adenosquamous carcinoma (LGASC) is a rare subtype of metaplastic breast carcinoma (MpBC), accounting for fewer than 0.05% of breast cancer cases. Unlike the typically aggressive nature of MpBCs, LGASC is an indolent tumor with an excellent prognosis. Due to its rarity, LGASC is frequently misdiagnosed, particularly in core needle biopsies. Currently, there are no clear treatment guidelines for LGASC. (2) Methods: This study presents a single-center retrospective analysis and a systematic literature review of LGASC. (3) Results: Three LGASC cases were diagnosed among 6462 breast cancer patients in our center, demonstrating its rarity. LGASC has overlapping features with benign sclerosing lesions and is often initially misdiagnosed. LGASC is often overtreated, as its indolent nature is not recognized. It very rarely presents axillary or distant metastases, and in contemporary data, local recurrences are rare, questioning the need for adjuvant therapy. (4) Conclusions: LGASC is a very rare form of breast cancer with an excellent prognosis despite being MpBC and usually a triple-negative breast cancer. It is often overtreated as its unique nature is not recognized.

A new subtype of papillary ductal carcinoma in situ with tall cell and reversed polarity morphology: a rare case report

BACKGROUND

According to previous studies, tall cell carcinoma with reversed polarity can be easily distinguished from ductal carcinoma in situ based on the absence of myoepithelium and a typical histologic feature. However, to the best of our knowledge, no cases of papillary ductal carcinoma exhibiting tall cell and reversed polarity features with intact myoepithelium have been reported, and thus its diagnosis and prognosis remain unclear.

CASE PRESENTATION

A 54-year-old female with a palpable lump in her right breast for 3 years. There were no other symptoms found. A preoperative ultrasound examination showed an oval, well-circumscribed, anechoic cystic appearance with hypoechoic adnexal nodules, classified as 3-4a in the Breast Imaging Reporting Data System. Surgical excision revealed an in-situ breast carcinoma exhibiting a solid papillary pattern and tall cell with reversed polarity of nuclei. After thorough postoperative pathology, immunohistochemistry, and next-generation sequencing, we hypothesized that it might be a new ductal carcinoma in situ subtype with tall cells and reversed polarity of the mammary gland.

CONCLUSIONS

We herein present a rare case of papillary ductal carcinoma in situ with tall cell and reversed polarity morphology breast cancer, which can closely mimic tall cell carcinoma with reversed polarity and ductal carcinoma in situ. Thorough evaluations of histologic features, immunohistochemistry results, and genetic alterations are significant in identifying this rare entity. In addition, this type of breast cancer is low-malignant and has a favorable prognosis without any adjuvant therapy after complete resection.

Fibromatosis-Like Metaplastic Carcinoma of the Breast: A Challenging Diagnosis With Potential Pitfalls

Fibromatosis-like metaplastic carcinoma (FLMC) is a rare subtype of metaplastic carcinoma of the breast. Diagnosing this entity poses significant challenges, particularly in core biopsies due to limited sampling and overlap with benign spindle cell lesions such as nodular fasciitis and fibromatosis. We present an example of FLMC in an asymptomatic middle-aged woman. As her breast imaging revealed an irregular lobulated mass, a core biopsy was performed which showed benign breast tissue with fibrosis. However, this was discordant with her imaging findings, hence a subsequent vacuum-assisted biopsy was done which revealed low-grade spindle cell proliferation, consistent with FLMC. This report emphasizes the necessity of a triple assessment and highlights the potential pitfalls in diagnosing FLMC, particularly the risk of misinterpretation due to its histological similarities with benign entities. Understanding these challenges will be crucial to avoid diagnostic delays of this rare breast cancer subtype.

Prognostic impact of histological subtyping in triple-negative breast cancer

The impact of special histological types (ST) in triple-negative breast cancer (TNBC) and its association with overall outcome has gained increasing relevance as survival has been linked to specific histological TNBC subtypes. We evaluated the clinicopathological and survival data of 598 patients with 613 TNBCs, including 464 TNBCs of no special type (NST) and 149 TNBCs ST (low-grade, n = 12, 8.1%; high-grade, n = 112, 75.2%; apocrine and androgen receptor-positive [APO AR], n = 25, 16.8%). Patients with low-grade TNBC ST and TNBC ST APO AR were significantly older (P < 0.001) and had a lower Ki67 index (P < 0.001) than those with TNBC NST. Patients with high-grade TNBC ST were significantly older (P = 0.006) and had poorer pathological responses to neoadjuvant chemotherapy (NAC) (P < 0.001) than those with TNBC NST. Significant survival differences were observed between low-grade TNBC ST, TNBC ST APO AR, high-grade TNBC ST, and TNBC NST in the entire study group (DFS, P = 0.002; DDFS, P = 0.001) and in the non-NAC subgroup (OS, P = 0.034; DFS, P = 0.001; DDFS, P < 0.001). Patients with low-grade TNBC ST had the best survival outcomes. Patients with high-grade TNBC ST showed significantly worse outcomes than those with TNBC NST (entire study group: OS, P = 0.049; DFS, P < 0.001; DDFS, P = 0.001; non-NAC subgroup: OS, P = 0.014; DFS, P < 0.001; DDFS, P < 0.001). We conclude that prognostic stratification of TNBC ST is ultimately important for optimizing the therapeutic management of patients with these rare tumor entities.

Hormone receptor expression in low-grade adenosquamous carcinoma of the breast progressing to high-grade metaplastic carcinoma: A case report

RATIONALE

Breast low-grade adenosquamous carcinoma is an uncommon cancer that has been neglected in genetic and pathophysiological research. Consequently, medical practitioners face challenges in the effective diagnosis and treatment of this condition.

PATIENT CONCERNS

We present the case of a 57-year-old Asian female patient who presented with bilateral breast masses on physical examination. Ultrasound and an MRI revealed a highly suspicious malignant mass in her right breast that was completely removed surgically.

DIAGNOSES

After pathological analysis, the diagnosis was low-grade adenosquamous carcinoma with local high-grade transformation, and some of the tumor components were estrogen receptor positive.

INTERVENTIONS

The patient underwent appropriate postoperative chemotherapy and achieved a favorable outcome.

OUTCOMES

During the follow-up period after surgical resection, the patient did not experience any local recurrence or distant metastasis.

LESSONS

Owing to the rare combination of estrogen receptor positivity and high-grade progression, this patient also required adjuvant chemotherapy. This enhances the essential foundation for diagnosing and treating this rare disease, and facilitates the implementation of treatment plans.

Molecular pathology in breast disease: diagnostic, prognostic, and therapeutic tools

Molecular testing in breast cancer gained increasing attention and importance as specific molecular results can tailor not only oncological decisions on systemic adjuvant or neoadjuvant or in metastatic setting, but increasingly serve in diagnostic routine histopathological services to differentiate between morphologically overlapping or ambiguous histological pictures. Diagnostic tools involve in most cases a broad spectrum of immunohistochemical panels, followed by entity-specific in situ hybridization probes and in given cases NGS-based sequencing. Workflow of which methodology is applied and in which order depends on the specific entity resp. on the given differential diagnosis in question. Regarding prognostic/predictive molecular testing, the choice of assay and the workflow are based on clinical algorithms and on the evidence of targeted therapies following the molecular alterations. In this review paper, we aim to address the use of molecular technics in [1] the histological diagnostic setting (such as subtyping of invasive carcinomas/malignant spindle cell tumors and sarcomas and some B3 lesions) and [2] in the context of adjuvant or neoadjuvant or other clinical settings with special focus of targeted therapies.

Low-grade adenosquamous carcinoma of the breast: a clinical, morphological and immunohistochemical analysis of 25 patients

AIMS

Due to its rarity and non-specific clinical and pathological features, low-grade adenosquamous carcinoma (LGASC) of the breast continues to pose diagnostic challenges. Unlike other triple-negative breast carcinomas, LGASC tends to have an indolent clinical behaviour. It is essential to recognise this lesion for accurate diagnosis and appropriate management.

METHODS AND RESULTS

Twenty-five cases of LGASC were identified in our archives and collaborating institutes. Cases of LGASC with dominant coexisting other type carcinomas were excluded. We studied the clinical presentation, morphological features, patterns of the commonly used immunohistochemical stains and follow-up. In our cohort, LGASC was commonly located at the outer aspect of the breast and associated with intraductal papilloma. The morphology of LGASC is characterised by infiltrating small glands and nests with variable squamous differentiation. We also found cuffing desmoplastic (fibrolamellar) stromal change in 75% of patients and peripheral lymphocytic aggregates in 87.5% of patients. P63 and smooth muscle myosin (SMM) were the most common myoepithelial markers used to assist in diagnosis. P63 often stained peripheral tumour cells surrounding invasive glands (circumferential staining in 80% of the cases), mimicking myoepithelial cells. It also stained the small nests with squamous differentiation. However, SMM was negative in 63% of the cases. The vast majority of our cases were triple-negative; only a few had focal and weak expressions of ER and PR. One patient who did not have excision developed lymph node metastasis. Most patients underwent excision or mastectomy with negative margins as surgical treatment; there were no recurrences or metastases in these patients with clinical follow-ups up to 108 months.

CONCLUSIONS

LGASC has some unique, although not entirely specific, morphological features and immunohistochemical staining patterns. Fibrolamellar stromal change, peripheral lymphocytic aggregates and variable staining of p63 and SMM are valuable features to facilitate the diagnosis.

[Triple-negative breast cancer : Classification, current concepts, and therapy-related factors]

Triple-negative breast cancer (TNBC) accounts for about 10% of all breast cancer cases and is defined by the lack of expression of estrogen and progesterone receptors and the lack of overexpression or amplification of HER2. It differs with regard to the younger age of the patients, an increased association with a mutation of BRCA1 and a mostly low differentiation from hormone receptor-positive breast cancer. The spectrum of triple-negative breast cancer shows considerable heterogeneity both at the morphological and at the molecular level. It includes most commonly TNBC of no special type, with and without basal phenotype, triple-negative metaplastic breast carcinomas, triple-negative breast carcinomas with apocrine differentiation and rare triple-negative tumor types. At the gene-expression level, TNBC most commonly is associated with a basal phenotype, with rarer molecular variants of TNBC involving the Claudin-low, molecular apocrine types, and other rarer subtypes. Therefore, a critical use of the term TNBC, considering the histopathological tumor differentiation, is recommended.

Breast lesions with myoepithelial phenotype

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

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.