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1.
Journal of Breast Cancer ; : 105-116, 2023.
Article in English | WPRIM | ID: wpr-976820

ABSTRACT

Purpose@#Oncotype DX (ODX) is a well-validated multigene assay that is increasingly used in Korean clinical practice. This study aimed to develop a clinicopathological prediction (CPP) model for the ODX recurrence scores (RSs). @*Methods@#A total of 297 patients (study group, n = 175; external validation group, n = 122) with estrogen receptor-positive, human epidermal growth factor receptor 2 (HER2)-negative, T1-3N0-1M0 breast cancer, and available ODX test results were included in the study. Risk categorization as determined by ODX RSs concurred with the TAILORx study (low-risk, RS ≤ 25; high-risk, RS > 25). Univariate and multivariate logistic regression analyses were used to assess the relationships between clinicopathological variables and risk stratified by the ODX RSs. A CPP model was constructed based on regression coefficients (β values) for clinicopathological variables significant by multivariate regression analysis. @*Results@#Progesterone receptor (PR) negativity, high Ki-67 index, and nuclear grade (NG) 3 independently predicted high-risk RS, and these variables were used to construct the CPP model. The C-index, which represented the discriminatory ability of our CPP model for predicting a high-risk RS, was 0.915 (95% confidence interval [CI], 0.859–0.971). When the CPP model was applied to the external validation group, the C-index was 0.926 (95% CI, 0.873–0.978). @*Conclusion@#Our CPP model based on PR, Ki-67 index, and NG could aid in the selection of patients with breast cancer requiring an ODX test.

2.
Annals of Dermatology ; : S10-S13, 2023.
Article in English | WPRIM | ID: wpr-976687

ABSTRACT

Spindle cell lipoma is a rare benign neoplasm that features a mixture of evenly aligned spindle cells, mature adipocytes, and ropey collagen. Most cases of spindle cell lipoma are found in the subcutaneous tissue, and intradermal spindle cell lipoma is rarely reported. We present a case of intradermal spindle cell lipoma in a 46-year-old female who presented with a 0.7-cm flesh-colored and dome-shaped nodule on the right temple that had developed 6 years ago. This mass was excised, and upon histopathologic examination, an unencapsulated lesion was located in the dermis, which consisted of bland spindle cells, scanty mature adipocytes, rare lipoblasts, and ropey collagen bundles with prominent basophilic myxoid stroma. Immunohistochemical staining showed diffuse positivity for CD34, negativity for the S-100 protein, and loss of retinoblastoma protein expression. Based on these features, intradermal low-fat spindle cell lipoma was diagnosed. No evidence of local recurrence was observed 4 months after excision. Intradermal low-fat spindle cell lipomas are extremely rare and can easily be mistaken for tumors that have similar clinical and histopathological findings. Herein, we report a globally rare case of an intradermal low-fat spindle cell lipoma.

3.
Annals of Dermatology ; : S25-S29, 2023.
Article in English | WPRIM | ID: wpr-976684

ABSTRACT

Superficial CD34-positive fibroblastic tumor (SCPFT) is a recently described disease entity characterized by marked nuclear pleomorphism, low mitotic count, and diffuse CD34 positivity. It is a rare, distinctive, low-grade fibroblastic neoplasm. To date, only 44 cases have been reported in the English-language literature. Herein, we report two cases of SCPFT involving a 48-year-old male and a 22-year-old male with superficial tumors on the right and left thighs, respectively. Excision was performed in both cases. Histologically, both tumors showed spindle-to-epithelioid cells arranged in fascicular or sheet-like patterns. Most cells displayed granular or eosinophilic glassy cytoplasm, marked nuclear pleomorphism, and a low mitotic rate. On immunohistochemical staining, tumor cells were diffusely positive for CD34 and negative for S100 protein, smooth muscle actin, and desmin. After wide excision, neither patient experienced recurrence or metastasis after 16 months and 11 months of clinical follow-up, respectively. To the best of our knowledge, these are the first two cases of SCPFT reported in Korea. We believe these case reports would contribute to the clinicopathological understanding of SCPFT and assist clinicians in differentiating this tumor from other superficial soft tissue neoplasms.

4.
Korean Journal of Dermatology ; : 352-359, 2023.
Article in English | WPRIM | ID: wpr-1002176

ABSTRACT

Background@#Inverted follicular keratosis (IFK) is a benign tumor that occurs mainly as a single lesion in the head and neck. Histologically, the tumor lobules show endophytic or exophytic growth and are characterized by squamous eddies. IFK should be differentiated from seborrheic keratosis, verruca vulgaris, and squamous cell carcinoma (SCC).In particular, differentiating from well-differentiated SCC can be difficult when downward growth is observed along with some mitotic figures and inflammatory cell infiltration. @*Objective@#To evaluate and compare the clinical and histopathological characteristics of IFK and well-differentiated SCC. @*Methods@#We retrospectively reviewed the clinicopathological records of 21 patients diagnosed with IFK and 21 randomly assigned patients diagnosed with well-differentiated SCC between 2000 and 2022 at the Dermatology Department of the Yeungnam University Medical Center. @*Results@#IFK occurs frequently on the head and neck of middle aged and older adults, and its average size is less than 1 cm. Acantholysis was observed in varying degrees in IFK; however, well-differentiated SCC was mostly absent (17 cases) or mild (three cases) showing a statistically significant difference. Squamous eddies were observed in 21 cases of IFK and eight of well-differentiated SCC. The average number of dyskeratotic cells and mitotic counts did not differ significantly between IFK and well-differentiated SCC. @*Conclusion@#We suggested some evidence for the irritant origin of IFK. We also compared the clinicohistological findings of IFK with those of well-differentiated SCC and concluded that excluding atypical cells, abnormal mitotic figures, and irregular invasive borders is important for differential diagnosis.

5.
Korean Journal of Dermatology ; : 92-99, 2023.
Article in English | WPRIM | ID: wpr-968065

ABSTRACT

Background@#Nodular hidradenoma is a relatively common benign cutaneous neoplasm, which usually presents as solitary intradermal nodule. In Korea, an extensive study on tumors with eccrine differentiation was performed in 2006; however, the study considered all eccrine tumors and detailed analysis of its differentiation was not performed. In addition, although most skin pathology textbooks classify it as a tumor showing eccrine differentiation, its differentiation remains controversial. @*Objective@#This study investigated clinicopathological features of nodular hidradenoma in Koreans at a tertiary referral center. @*Methods@#We retrospectively investigated 22 patients who presented with nodular hidradenoma at Yeungnam University Hospital between 2000 and 2021. Diagnosis was confirmed by histopathological examination in all the patients. @*Results@#About half of the lesions were located on the head and neck area (45.5%), followed by the trunk (31.8%). Histopathological examination revealed that tumor cells in most of the cases consisted of cuboidal and clear cells; however, in some cases there were several specific modified cells such as clear cells (9.1%), squamoid cells (4.5%), and poroid cells (22.7%). Considering the morphological characteristic of tubular structures, most cases (90.9%) showed apocrine differentiation, and only 2 cases (9.1%) showed eccrine differentiation. @*Conclusion@#Considering the characteristics of cells and tubular structures constituting tumors, it is reasonable to consider nodular hidradenoma as a tumor with apocrine differentiation rather than with eccrine differentiation, which had previously been the predominant classification. Furthermore, there still is no distinct marker for determining whether cells differentiate into eccrine or apocrine tissues and further studies are therefore needed.

6.
Korean Journal of Dermatology ; : 697-700, 2022.
Article in English | WPRIM | ID: wpr-968041

ABSTRACT

Piloleiomyoma originates from the arrector pili muscles. Multiple piloleiomyoma lesions may occur, especially on the trunk and extremities. However, multiple lesions throughout the body are rare. We present a case of generalized cutaneous piloleiomyomatosis in a 72-year-old man who had numerous lesions throughout his body. Clinically, the patient presented with fixed and non-tender reddish to brownish papules and nodules mainly on the back and extensors of extremities. Punch biopsy was performed, and the specimen was stained with hematoxylin and eosin, revealing interweaving fascicles of cigar-like spindle cells on the upper dermis. On immunohistochemical staining, tumor cells were positive for smooth muscle actin. Based on these features, we diagnosed the patient with generalized cutaneous piloleiomyomatosis.

7.
Journal of Pathology and Translational Medicine ; : 289-297, 2021.
Article in English | WPRIM | ID: wpr-900483

ABSTRACT

Background@#Cutaneous metastasis (CM) is the spread of cancer cells from a primary site to the skin and is rarely the first sign of silent cancer. We investigated the clinicopathological characteristics of CM from internal malignancies in Korean patients treated at our institution over 20 years. @*Methods@#The clinicopathological findings of 112 patients (62 females, 50 males) with CM diagnosed at Yeungnam University Hospital between 2000 and 2020 were retrospectively reviewed. @*Results@#Mean patient age was 58.6 years (range, 26 to 87 years), and the most common primary cancer site was breast (74.2%) in women and lung (36.0%) in men. Ninety-six patients (85.7%) presented with CM after primary tumor diagnosis. CM from the lung or biliary tract usually occurred within 2 years of primary tumor diagnosis, whereas metastases from the breast and kidney occurred several years later. The chest, abdomen, and scalp were common sites of CM. Breast cancer usually metastasized to chest skin, while gastrointestinal tract cancers commonly metastasized to the abdomen. The scalp was a common location for CM from various tumors. The most common dermatologic presentations were nodules and masses. Immunohistochemical studies helped identify underlying malignancies when primary tumors were unknown. @*Conclusions@#The relative frequency of CM parallels the overall incidence of primary malignant tumors, and CMs usually occur at anatomic sites close to the primary tumor. CM can be diagnosed based on clinical, radiological, and histological features; however, immunohistochemical study is required in some cases.

8.
Journal of Breast Disease ; (2): 16-25, 2021.
Article in English | WPRIM | ID: wpr-899025

ABSTRACT

Purpose@#This study aimed to determine the clinicopathologic factors, including tumor elasticity, affecting neoadjuvant chemotherapy response in breast cancer. @*Methods@#Among 95 patients who received neoadjuvant chemotherapy for clinical stage IIa-IIIc primary breast cancer, 75 underwent strain elastography assessments. The patients were divided into soft and hard tumor groups based on the Tsukuba elasticity scoring system. Pathologic factors, including tumor cellularity and stromal characteristics, were evaluated using core needle biopsy specimens collected before neoadjuvant chemotherapy. Pathologic complete response (pCR) was defined as the absence of invasive carcinoma in the breast and axillary lymph nodes. Residual cancer burden (RCB) was also calculated in 79 cases. @*Results@#Twenty-two patients achieved pCR (23.2%). The rates of estrogen receptor (ER) negativity (p=0.04), progesterone receptor (PR) negativity (p=0.03), and nuclear grade 3 (p=0.03) were higher in patients with pCR than those in patients without pCR. The rates of PR negativity (p=0.03), nuclear grade 3 (p=0.01), and high tumor-infiltrating lymphocyte (TIL) levels (p=0.04) were significantly higher in the favorable RCB group (RCB-0 and I) than those in the unfavorable RCB group (RCB-II and III). No significant difference in tumor elasticity was observed between the groups (p=0.30). Hormone receptor (HR) negativity was an independent predictor of favorable RCB in the multivariate analysis (p=0.04). @*Conclusion@#Tumor elasticity was not associated with pCR or RCB. HR negativity was an independent predictor of favorable RCB.

9.
Journal of Breast Cancer ; : 1-21, 2021.
Article in English | WPRIM | ID: wpr-898999

ABSTRACT

Given the recent advances in management and understanding of breast cancer, a standardized pathology report reflecting these changes is critical. To meet this need, the Breast Pathology Study Group of the Korean Society of Pathologists has developed a standardized pathology reporting format for breast cancer, consisting of ‘standard data elements,’ ‘conditional data elements,’ and a biomarker report form. The ‘standard data elements’ consist of the basic pathologic features used for prognostication, while other factors related to prognosis or diagnosis are described in the ‘conditional data elements.’ In addition to standard data elements, all recommended issues are also presented. We expect that this standardized pathology report for breast cancer will improve diagnostic concordance and communication between pathologists and clinicians, as well as between pathologists inter-institutionally.

10.
Journal of Breast Cancer ; : 164-174, 2021.
Article in English | WPRIM | ID: wpr-898981

ABSTRACT

Purpose@#In this trial, we investigated the efficacy and safety of adjuvant letrozole for hormone receptor (HR)-positive breast cancer. Here, we report the clinical outcome in postmenopausal women with HR-positive breast cancer treated with adjuvant letrozole according to estrogen receptor (ER) expression levels. @*Methods@#In this multi-institutional, open-label, observational study, postmenopausal patients with HR-positive breast cancer received adjuvant letrozole (2.5 mg/daily) for 5 years unless they experienced disease progression or unacceptable toxicity or withdrew their consent. The patients were stratified into the following 3 groups according to ER expression levels using a modified Allred score (AS): low, intermediate, and high (AS 3–4, 5–6, and 7–8, respectively). ER expression was centrally reviewed. The primary objective was the 5-year disease-free survival (DFS) rate. @*Results@#Between April 25, 2010, and February 5, 2014, 440 patients were enrolled. With a median follow-up of 62.0 months, the 5-year DFS rate in all patients was 94.2% (95% confidence interval [CI], 91.8–96.6). The 5-year DFS and recurrence-free survival (RFS) rates did not differ according to ER expression; the 5-year DFS rates were 94.3% and 94.1%in the low-to-intermediate and high expression groups, respectively (p = 0.6), and the corresponding 5-year RFS rates were 95.7% and 95.4%, respectively (p = 0.7). Furthermore, 25 patients discontinued letrozole because of drug toxicity. @*Conclusion@#Treatment with adjuvant letrozole showed very favorable treatment outcomes and good tolerability among Korean postmenopausal women with ER-positive breast cancer, independent of ER expression.

11.
Journal of Pathology and Translational Medicine ; : 289-297, 2021.
Article in English | WPRIM | ID: wpr-892779

ABSTRACT

Background@#Cutaneous metastasis (CM) is the spread of cancer cells from a primary site to the skin and is rarely the first sign of silent cancer. We investigated the clinicopathological characteristics of CM from internal malignancies in Korean patients treated at our institution over 20 years. @*Methods@#The clinicopathological findings of 112 patients (62 females, 50 males) with CM diagnosed at Yeungnam University Hospital between 2000 and 2020 were retrospectively reviewed. @*Results@#Mean patient age was 58.6 years (range, 26 to 87 years), and the most common primary cancer site was breast (74.2%) in women and lung (36.0%) in men. Ninety-six patients (85.7%) presented with CM after primary tumor diagnosis. CM from the lung or biliary tract usually occurred within 2 years of primary tumor diagnosis, whereas metastases from the breast and kidney occurred several years later. The chest, abdomen, and scalp were common sites of CM. Breast cancer usually metastasized to chest skin, while gastrointestinal tract cancers commonly metastasized to the abdomen. The scalp was a common location for CM from various tumors. The most common dermatologic presentations were nodules and masses. Immunohistochemical studies helped identify underlying malignancies when primary tumors were unknown. @*Conclusions@#The relative frequency of CM parallels the overall incidence of primary malignant tumors, and CMs usually occur at anatomic sites close to the primary tumor. CM can be diagnosed based on clinical, radiological, and histological features; however, immunohistochemical study is required in some cases.

12.
Journal of Breast Disease ; (2): 16-25, 2021.
Article in English | WPRIM | ID: wpr-891321

ABSTRACT

Purpose@#This study aimed to determine the clinicopathologic factors, including tumor elasticity, affecting neoadjuvant chemotherapy response in breast cancer. @*Methods@#Among 95 patients who received neoadjuvant chemotherapy for clinical stage IIa-IIIc primary breast cancer, 75 underwent strain elastography assessments. The patients were divided into soft and hard tumor groups based on the Tsukuba elasticity scoring system. Pathologic factors, including tumor cellularity and stromal characteristics, were evaluated using core needle biopsy specimens collected before neoadjuvant chemotherapy. Pathologic complete response (pCR) was defined as the absence of invasive carcinoma in the breast and axillary lymph nodes. Residual cancer burden (RCB) was also calculated in 79 cases. @*Results@#Twenty-two patients achieved pCR (23.2%). The rates of estrogen receptor (ER) negativity (p=0.04), progesterone receptor (PR) negativity (p=0.03), and nuclear grade 3 (p=0.03) were higher in patients with pCR than those in patients without pCR. The rates of PR negativity (p=0.03), nuclear grade 3 (p=0.01), and high tumor-infiltrating lymphocyte (TIL) levels (p=0.04) were significantly higher in the favorable RCB group (RCB-0 and I) than those in the unfavorable RCB group (RCB-II and III). No significant difference in tumor elasticity was observed between the groups (p=0.30). Hormone receptor (HR) negativity was an independent predictor of favorable RCB in the multivariate analysis (p=0.04). @*Conclusion@#Tumor elasticity was not associated with pCR or RCB. HR negativity was an independent predictor of favorable RCB.

13.
Journal of Breast Cancer ; : 1-21, 2021.
Article in English | WPRIM | ID: wpr-891295

ABSTRACT

Given the recent advances in management and understanding of breast cancer, a standardized pathology report reflecting these changes is critical. To meet this need, the Breast Pathology Study Group of the Korean Society of Pathologists has developed a standardized pathology reporting format for breast cancer, consisting of ‘standard data elements,’ ‘conditional data elements,’ and a biomarker report form. The ‘standard data elements’ consist of the basic pathologic features used for prognostication, while other factors related to prognosis or diagnosis are described in the ‘conditional data elements.’ In addition to standard data elements, all recommended issues are also presented. We expect that this standardized pathology report for breast cancer will improve diagnostic concordance and communication between pathologists and clinicians, as well as between pathologists inter-institutionally.

14.
Journal of Breast Cancer ; : 164-174, 2021.
Article in English | WPRIM | ID: wpr-891277

ABSTRACT

Purpose@#In this trial, we investigated the efficacy and safety of adjuvant letrozole for hormone receptor (HR)-positive breast cancer. Here, we report the clinical outcome in postmenopausal women with HR-positive breast cancer treated with adjuvant letrozole according to estrogen receptor (ER) expression levels. @*Methods@#In this multi-institutional, open-label, observational study, postmenopausal patients with HR-positive breast cancer received adjuvant letrozole (2.5 mg/daily) for 5 years unless they experienced disease progression or unacceptable toxicity or withdrew their consent. The patients were stratified into the following 3 groups according to ER expression levels using a modified Allred score (AS): low, intermediate, and high (AS 3–4, 5–6, and 7–8, respectively). ER expression was centrally reviewed. The primary objective was the 5-year disease-free survival (DFS) rate. @*Results@#Between April 25, 2010, and February 5, 2014, 440 patients were enrolled. With a median follow-up of 62.0 months, the 5-year DFS rate in all patients was 94.2% (95% confidence interval [CI], 91.8–96.6). The 5-year DFS and recurrence-free survival (RFS) rates did not differ according to ER expression; the 5-year DFS rates were 94.3% and 94.1%in the low-to-intermediate and high expression groups, respectively (p = 0.6), and the corresponding 5-year RFS rates were 95.7% and 95.4%, respectively (p = 0.7). Furthermore, 25 patients discontinued letrozole because of drug toxicity. @*Conclusion@#Treatment with adjuvant letrozole showed very favorable treatment outcomes and good tolerability among Korean postmenopausal women with ER-positive breast cancer, independent of ER expression.

15.
Yeungnam University Journal of Medicine ; : 78-82, 2021.
Article in English | WPRIM | ID: wpr-875560

ABSTRACT

Pancreatic metastasis from malignant phyllodes tumor (PT) of the breast is rare, and only a few cases have been reported in the literature. Here, we report a case of pancreatic metastasis from malignant PT of the breast in a 48-year-old woman. She had had three episodes of recurrence of malignant PT in her right breast. She presented with epigastric pain for 2 months. Computed tomography and magnetic resonance imaging revealed a 6 cm-sized, well-defined, heterogeneous mass with peripheral enhancement in the body of the pancreas. Endoscopic ultrasonography-guided fine-needle aspiration was performed, and the pathologic report suggested spindle cell mesenchymal neoplasm. Subsequently, surgical excision was performed, and the mass was confirmed as a metastatic malignant PT. The imaging findings are discussed and the literature is briefly reviewed in this report.

16.
Journal of Pathology and Translational Medicine ; : 1-15, 2021.
Article in English | WPRIM | ID: wpr-874885

ABSTRACT

Given the recent advances in management and understanding of breast cancer, a standardized pathology report reflecting these changes is critical. To meet this need, the Breast Pathology Study Group of the Korean Society of Pathologists has developed a standardized pathology reporting format for breast cancer, consisting of ‘standard data elements,’ ‘conditional data elements,’ and a biomarker report form. The ‘standard data elements’ consist of the basic pathologic features used for prognostication, while other factors related to prognosis or diagnosis are described in the ‘conditional data elements.’ In addition to standard data elements, all recommended issues are also presented. We expect that this standardized pathology report for breast cancer will improve diagnostic concordance and communication between pathologists and clinicians, as well as between pathologists inter-institutionally.

17.
Ultrasonography ; : 298-310, 2020.
Article | WPRIM | ID: wpr-835341

ABSTRACT

A wide range of breast lesions can arise during pregnancy and lactation, from benign or Epub ahead of print inflammatory diseases to malignant tumors. Hormone-influenced physiological changes of the breast make the radiological evaluation of breast lesions challenging. Knowledge of the imaging features of normal physiological changes and common breast lesions during this period can help radiologists accurately diagnose and appropriately manage conditions. As such, this pictorial essay illustrates normal physiological changes related to pregnancy and lactation, as well as common benign and malignant breast lesions encountered during those periods.

18.
Korean Journal of Dermatology ; : 312-317, 2020.
Article | WPRIM | ID: wpr-832711

ABSTRACT

Background@#Lichen planus-like keratosis (LPLK), also known as benign lichenoid keratosis, usually presents as a single, brown to red, scaly, flat-topped plaque. Several large-scale studies have reported LPLK in Caucasians; however, no study has reported LPLK in Koreans. @*Objective@#To investigate the clinicopathological features of LPLK in Koreans. @*Methods@#We retrospectively investigated 60 patients with LPLK at Yeungnam University Hospital between 2001 and 2019. Diagnosis of LPLK was confirmed by histopathological examination in all patients. @*Results@#Most patients (96.6%) had a single lesion. The most common location was the face (63.3%), followed by the trunk (16.7%), and upper extremities (11.7%). Mean patient age was 62.7 years, and the female:male ratio was 1.3:1. The initial clinical impression involved seborrheic keratosis in 56.7% of cases and LPLK in only 16.7% of cases. Solar elastosis (58.3%) and red blood cell extravasation (55%) were also commonly observed in this study population. Histopathological findings revealed focal parakeratosis (35%), dermal eosinophils (30%), and plasma cells (10%). @*Conclusion@#LPLK may commonly be misdiagnosed, because it is often clinically indistinguishable from seborrheic keratosis and other epithelial neoplasms. Skin biopsy findings and clinicopathological correlation are therefore necessary for differential diagnosis. Several histopathological features, such as parakeratosis as well as dermal eosinophil and plasma cell infiltration, can distinguish LPLK from lichen planus.

20.
Journal of Breast Cancer ; : 484-497, 2020.
Article in English | WPRIM | ID: wpr-898969

ABSTRACT

Purpose@#In 2007, the American Society of Clinical Oncology and the College of American Pathologists had established a human epidermal growth factor receptor 2 (HER2) testing guideline, which was updated in 2013 and subsequently in 2018. We assessed the clinical impact of the recent update by comparing the in situ hybridization (ISH) results based on the 2007, 2013, and 2018 guidelines. @*Methods@#We assessed 2 cohorts. The first cohort included 1,161 primary invasive breast cancer (IBC) samples including 18 bilateral IBC cases, with both immunohistochemistry (IHC) and silver-enhanced ISH (SISH) results available for the HER2 status. The second cohort included 160 IBC cases with equivocal HER2 IHC, assessed using SISH. We retrospectively evaluated and compared the HER2 SISH results. @*Results@#There were 22 (1.9%) and 20 (12.5%) cases with altered SISH results according to the 2013 guidelines in cohorts 1 and 2, respectively. As per the 2018 guidelines, final HER2 statuses of 16 (1.4%) and 14 (8.5%) cases changed in cohorts 1 and 2, respectively. The 2013 guidelines increased the positive rate compared to the 2007 guidelines, in both cohorts (0.6% and 6.2%, respectively). Most equivocal cases in cohorts 1 (92.3%) and 2 (100%) as per the 2013 guidelines were reclassified as HER2-negative according to the 2018 guidelines.The 2018 guidelines increased the negative rates (1.3% in cohort 1 and 8.7% in cohort 2) and slightly decreased the positive rates (−0.2% in cohort 1 and −3.1% in cohort 2), compared to the 2013 guidelines. With each update, minor changes in the positive and negative rates were observed in whole breast cancer samples (cohort 1). However, the 2018 guidelines affected previously defined HER2-positive IBC with equivocal IHC results. @*Conclusion@#Under the 2013 guidelines, the positive and equivocal cases increased. However, the 2018 guidelines eliminated ambiguous cases by reclassifying them as HER2-negative.

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