الفهرس 
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Abstract
Invasive breast carcinoma (IBC) is the most diagnosed malignant tumor in women and the leading cause of cancer-related deaths all over the world. BC incidence is steadily rising representing 36% of whole oncological patients. Triple-negative breast cancer (TNBC) is a diverse collection of tumors that accounts for 10–20 % of invasive breast cancers.
TNBC is often characterized by the lack of estrogen receptors, progesterone receptors, and HER2. It has extremely aggressive cancer features with a high rate of early relapses and a very bad prognosis overall. Due to the low sensitivity and specificity of standard breast origin markers such as mammaglobin and gross cystic disease fluid protein (GCDFP15).
It is expected that pathologists are excited about using the GATA3 and SOX10 immunohistochemical markers to confirm breast as the origin of metastatic tumors. However, the utility of GATA3 is limited by a lower coverage of ER-negative breast cancers, particularly for TNBC. GATA3 reported detecting 42-87% of TNBC, as well as a lack of specificity due to its expression in a variety of carcinomas from other sites, such as the salivary gland, skin adnexa, pancreas, liver, endometrium, and urothelium.
Therefore, it is extremely desirable to discover new molecular targets with high sensitivity and specificity for TNBC to enable prompt and accurate detection particularly of metastatic TNBC for routine surgical and pathological diagnosis.
SOX10 is a transcription factor expressed in many different cells and tissues including Schwann cells of peripheral nerves, epidermal melanocytes, and acinar cells of mammary and corresponding tumors. SOX10 expression in IBCs was reported as very sensitive to TNBCs, especially those with a basal-like phenotype. Thus, SOX10 may serve as a novel putative biomarker for predicting the prognosis and metastasis of primary TNBC and a potential therapeutic target gene for TNBC treatment.
The aim of our study was to evaluate the immunohistochemical expression of SOX10 in breast cancer and to evaluate its expression in triple-negative breast cancer in comparison to other subtypes.
This retrospective study included eighty-three cases collected randomly from archival paraffin blocks of breast cancers during the period from 2019 to 2023. Sections were prepared from paraffin blocks and the slides were immunohistochemically stained with SOX10 antibody.
The patient’s age in studied cases ranged from 26 to 83 years with a mean of 52.64 years old. Female patients were predominantly represented (97.6%) with male to female ratio of 1:10. The studied cases were divided into two groups: 62 cases of TNBC & 21 cases of non-TNBC which included (11 cases of Luminal A&B type, and 10 cases of Her2 positive type).
The studied cases comprised 72 cases (86.7%) of invasive breast carcinoma (NST), 2 cases (2.4%) of invasive lobular carcinoma (ILC), 6 cases (7.2%) of metaplastic carcinoma, and 3 cases (3.6%) breast carcinoma with medullary-like features. The tumor grade of the studied cases was grade II and grade III representing (59.0%) and (41.0%) respectively.
In the present study, no statistically significant relationship was reported between SOX10 expression and clinicopathological parameters, including age, sex, specimen procedure, tumor type, or tumor grade. Also, there was no significant correlation between SOX10 expression and the T-stage of the tumor, lymph node metastasis / N-stage of the tumor.
A highly significant difference was detected regarding SOX10 expression in TNBC compared to non-TNBC groups with the SOX10 positivity in the TNBC group. Positive SOX10 staining was detected in 39 cases (62.9%) of the TNBC group. On the other hand, positive SOX10 staining was detected in only 3 cases (14.3%) of the non-TNBC group.
Also, the results of this study revealed highly significant differences between SOX10 expression and different molecular subtypes of breast cancer groups. Positive expression of SOX10 in TNBC was significantly higher than that in other molecular subtypes, as its expression was inversely correlated with that of luminal and HER2 positive groups.
from the current study, we concluded that SOX10 is a potentially reliable marker for triple-negative breast carcinoma (TNBC). SOX10 is a valuable immunohistochemical marker that can be added in a panel with other breast-specific markers in the setting of metastasis of unknown primary origin, especially where mammary origin is doubted