The Added Value of SOX10 Immunohistochemistry to Other Breast Markers in Identifying Cytokeratin 5-Positive Triple Negative Breast Cancers as of Mammary Origin

Immunohistochemical Profile of Triple-Negative Breast Cancers: SOX10 and AR Dual Negative Tumors Have Worse Outcomes

Triple-negative breast cancer (TNBC) refers to an estrogen receptor-negative, progesterone receptor-negative, and HER2-negative breast cancer. Although accepted as a clinically valid category, TNBCs are heterogeneous at the histologic, immunohistochemical, and molecular levels. Gene expression profiling studies have molecularly classified TNBCs into multiple groups, but the prognostic significance is unclear except for a relatively good prognosis for the luminal androgen receptor subtype. Immunohistochemistry (IHC) has been used as a surrogate for basal and luminal subtypes within TNBC, but prognostication of TNBC using IHC is not routinely performed. We aimed to study immunophenotypic correlations in a well-annotated cohort of consecutive TNBCs, excluding postneoadjuvant chemotherapy cases. Tissue microarrays were constructed from a total of 245 TNBC cases. IHC stains were performed and consisted of luminal (AR and INPP4B), basal (SOX10, nestin, CK5, and EGFR), and diagnostic (GCDFP15, mammaglobin, GATA3, and TRPS1) markers. Survival analysis was performed to assess the significance of clinical-pathologic variables including age, histology, grade, lymphovascular invasion, Nottingham prognostic index category, American Joint Committee on Cancer (AJCC) stage, stromal tumor-infiltrating lymphocytes at 10% increment, CD8+ T-cell count, Ki-67 index, PD-L1 status, and chemotherapy along with the results of IHC markers. Apocrine tumors show prominent reactivity for luminal markers and GCDFP15, whereas no special-type carcinomas are often positive for basal markers. TRPS1 is a sensitive marker of breast carcinoma but shows low or no expression in apocrine tumors. High AJCC stage, lack of chemotherapy, and dual SOX10/AR negativity are associated with worse outcomes on both univariable and multivariable analyses. Lymphovascular invasion and higher Nottingham prognostic index category were associated with worse outcomes on univariable but not multivariable analysis. The staining for IHC markers varies based on tumor histology, which may be considered in determining breast origin. Notably, we report that SOX10/AR dual negative status in TNBC is associated with a worse prognosis along with AJCC stage and chemotherapy status.

Comparative expression of TRPS1, GATA3, SOX10, mammaglobin, and GCDFP-15 in effusion specimens with breast carcinoma

BACKGROUND

Traditional immunohistochemistry (IHC) for breast carcinomas has shown low detection rates of metastatic breast carcinoma (MBC) in effusions. Although GATA3 has enhanced diagnostic accuracy in this realm, its limited utility in detecting triple-negative breast carcinoma (TNBC) has been highlighted. TRPS1 has been introduced as a potentially sensitive and specific marker in detecting MBC on histologic samples. We investigate the utility of TRPS1 as a marker for MBC in effusion specimens and compare its performance to SOX10, GATA3, mammaglobin (MG), and GCDFP-15.

METHODS

A database search identified malignant effusions involved by MBC between 2013 and 2021. Cases from unique patients with sufficient cellularity were evaluated for TRPS1, GATA3, SOX10, MG, and GCDFP-15 IHC. The intensity and extent of tumor cells (TC) were scored by two pathologists. Any discrepancies were jointly reviewed for consensus.

RESULTS

GATA3 showed the highest rate of positivity (98.2%), followed by TRPS1 (89.5%), MG (43.9%), GCDFP-15 (21.1%), and SOX10 (3.5%). All GATA3-positive cases showed intermediate to high expression. Comparatively, TRPS1 showed more variability in staining extent and intensity. In 13 (22.8%) cases, TRPS1 showed extensive background staining of inflammatory and mesothelial cells. Of six TNBCs, GATA3, and TRPS1 were positive in six (100%) and four (66.7%) cases, respectively.

CONCLUSIONS

While TRPS1 shows a lower detection rate for MBC than GATA-3, using a combination of these markers can enhance effusion cytology's performance in detecting MBC. However, variability in TRPS1 staining intensity and high background TRPS1 staining of inflammatory and mesothelial cells can increase difficulty in its evaluation.

TRPS1 expression in cytokeratin 5 expressing triple negative breast cancers, its value as a marker of breast origin

The lack of oestrogen receptor, progesterone receptor and human epidermal growth factor receptor-2 expression in breast cancer (BC) is the basis for the categorization of the tumour as triple negative breast carcinoma (TNBC). The majority of TNBCs are aggressive tumours with common metastases and decreased expression of markers that could help in identifying the metastatic lesion as of mammary origin. Breast markers, such as gross cystic disease fluid protein-15 (GCDPF-15), GATA binding protein 3 (GATA3), mammaglobin (MGB) and SOX10, are not uniquely specific to BC. Our aim was to evaluate trichorhinophalangeal syndrome type 1 (TRPS1) protein as a breast marker in a series of cytokeratin-5-expressing TNBC, mostly corresponding to basal-like TNBCs, previously characterized for the expression of other breast markers. One hundred seventeen TNBCs in tissue microarrays were immunostained for TRPS1. The cut-off for positivity was ≥ 10%. The reproducibility of this classification was also assessed. TRPS1 positivity was detected in 92/117 (79%) cases, and this exceeded the expression of previously tested markers like SOX10 82 (70%), GATA3 11 (9%), MGB 10 (9%) and GCDFP-15 7 (6%). Of the 25 TRPS1-negative cases, 11 were positive with SOX10, whereas 5 to 6 dual negatives displayed positivity for the other makers. The evaluation showed substantial agreement. Of the five markers compared, TRPS1 seems the most sensitive marker for the mammary origin of CK5-expressing TNBCs. Cases that are negative are most often labelled with SOX10, and the remainder may still demonstrate positivity for any of the 3 other markers. TRPS1 has a place in breast marker panels.

Wnt Family Member 9b (Wnt9b) Is a Sensitive and Specific Marker for Triple-negative Breast Carcinoma Including Metaplastic Carcinoma

Wnt9b was recently identified as a highly sensitive and specific marker for breast carcinomas. Due to the limited number of triple-negative breast carcinomas (TNBCs) in previous study, we further explored Wnt9b's utility in breast carcinoma, especially in TNBCs including metaplastic carcinomas. We systematically evaluated Wnt9b expression on tissue microarrays (TMAs) from 413 breast carcinomas, 208 urothelial carcinomas, 102 endometrial carcinomas, 109 cholangiocarcinomas, 192 ovarian carcinomas, 48 lung adenocarcinomas, 69 colorectal adenocarcinomas, and 78 melanomas, and whole tissue section (WTS) from 20 human epidermal growth factor receptor 2-positive, 34 nonmetaplastic TNBCs, and 67 invasive metaplastic carcinomas. The results showed Wnt9b was highly expressed in breast carcinomas (91% on TMA and 98% on WTS) and in nonmetaplastic TNBCs (91% on TMA and 97% on WTS), but almost completely negative in other tested tumor types. Wnt9b was also highly expressed in metaplastic carcinomas (80%), significantly higher than GATA3 (56%) and SOX10 (48%), but slightly lower than TRPS1 (90%). In summary, our results demonstrate that Wnt9b is a highly sensitive marker for breast carcinomas, including TNBCs and metaplastic carcinomas. Further, we compared its utility with other breast markers including TRPS1, GATA3, and SOX10 in metaplastic carcinomas.

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.

Pitfalls in breast pathology

Accurate pathological diagnosis is the cornerstone of optimal clinical management for patients with breast disease. As non-operative diagnosis has now become the standard of care, histopathologists encounter the daily challenge of making definitive diagnoses on limited breast core needle biopsy (CNB) material. CNB samples are carefully evaluated using microscopic examination of haematoxylin and eosin (H&E)-stained slides and supportive immunohistochemistry (IHC), providing the necessary information to inform the next steps in the patient care pathway. Some entities may be difficult to distinguish on small tissue samples, and if there is uncertainty a diagnostic excision biopsy should be recommended. This review discusses (1) benign breast lesions that may mimic malignancy, (2) malignant conditions that may be misinterpreted as benign, (3) malignant conditions that may be incorrectly diagnosed as primary breast carcinoma, and (4) some IHC pitfalls. The aim of the review is to raise awareness of potential pitfalls in the interpretation of breast lesions that may lead to underdiagnosis, overdiagnosis, or incorrect classification of malignancy with potential adverse outcomes for individual patients.

Clinicopathologic and Molecular Characteristics of and Diagnostic Dilemmas in Invasive Breast Carcinoma with Choriocarcinomatous Pattern apropos a New Case: A Literature Review with New Findings

BACKGROUND

Invasive breast carcinoma with a choriocarcinomatous pattern (IBC-CP) is extremely rare, and its molecular basis is yet unclear. The choriocarcinomatous pattern is characterized by the biphasic arrangement of multinucleated syncytiotrophoblast-like cells around clusters of monotypic tumor cells in a hemorrhagic background, along with β-human chorionic gonadotropin (β-hCG) expression. The differentiation of IBC-CP from metastatic choriocarcinoma of the breast (MC-B) is difficult due to the histologic similarity.

METHODS

Based on a literature review and our own case, the clinicopathologic differences between IBC-CP patients (n = 17) and MC-B patients (n = 8) were analyzed. Moreover, in our case of IBC-CP, next-generation sequencing (NGS) comparative analysis was conducted for both choriocarcinomatous and invasive breast carcinoma (IBC) components.

RESULTS

Compared to the MC-B patients, the IBC-CP patients were older (p < 0.001) and less frequently had past histories of gestational trophoblastic disease/pregnancy/abortion (p = 0.001) and distant metastases (p = 0.005). Our case, a 49-year-old female patient, presented with masses in the right breast and axilla. Following neoadjuvant chemotherapy, a radical mastectomy found an 8.5-cm-sized tumor. Microscopically, multinucleated syncytiotrophoblast-like cells were observed around mononuclear tumor cells with hemorrhage and necrosis. Some tumor cells showed β-hCG immunopositivity, which was compatible with IBC-CP. NGS results showed a missense mutation in exon 5 of the TP53 gene in both the choriocarcinomatous and IBC components. Meanwhile, copy number loss in the PTEN gene was only identified in the choriocarcinomatous components.

CONCLUSION

The present IBC-CP case is triple-negative breast cancer with TP53 mutation. The PTEN gene may be associated with choriocarcinomatous differentiation. Obtaining a medical history is mandatory to exclude metastatic lesions.

The Utility of SOX10 Immunohistochemical Staining in Breast Pathology

OBJECTIVES

SOX10 expression helps identify melanocytic lesions. Over time, novel uses have been identified, such as expression in triple-negative breast cancer (TNBC). We evaluated the usefulness of SOX10 in breast pathology-specifically, identification and subtyping of TNBC and distinction from gynecologic carcinomas, use as a myoepithelial marker, and in the distinction of usual ductal hyperplasia (UDH) from atypical ductal hyperplasia (ADH).

METHODS

Several breast and gynecologic carcinoma tissue microarrays containing a total of 492 cases were stained with SOX10. Whole sections of 34 ADH, 50 UDH, and 29 ductal carcinoma in situ (DCIS) samples were also stained with SOX10.

RESULTS

SOX10 expression was identified in 67% of consecutive TNBC cases. Expression was mostly seen in nonapocrine, androgen receptor (AR)-negative TNBCs. All gynecologic carcinomas (n = 157) were negative. All UDH cases showed mosaic SOX10 expression, while all ADH cases lacked expression. All estrogen receptor (ER)-positive DCIS (n = 19) specimens were negative for SOX10, while 2 of 10 ER-negative DCIS specimens were positive for SOX10. The latter 2 cases showed SOX10-positive invasive carcinomas.

CONCLUSIONS

SOX10 identifies nonluminal AR-type TNBC and is useful in distinguishing TNBC from gynecologic carcinomas. SOX10 can distinguish UDH from ADH. SOX10 is not useful in distinguishing ADH from DCIS.