Mixed Adenosquamous Cell Carcinoma of the Prostate with Paired Sequencing on the Primary and Liver Metastasis.

This report aims to shed light on the intricate challenges encountered during the diagnosis and treatment of an uncommon variant of prostate cancer-mixed adenosquamous cell carcinoma of the prostate. Prostate cancers of this nature pose distinctive diagnostic and therapeutic dilemmas due to their rarity and complex histological composition. We present a case of a 63-year-old man with metastatic prostate cancer, featuring adenocarcinoma with squamous cell differentiation, who underwent a multimodal treatment approach. The patient responded to first-line carboplatin, docetaxel, and androgen deprivation therapy, followed by androgen receptor pathway inhibitor (ARPI) maintenance. However, disease progression led to radiation therapy and a subsequent switch to Lutetium (177Lu) vipivotide tetraxetan after chemotherapy challenges. Comprehensive genetic profiling revealed shared mutations in the prostate and liver lesions, emphasizing the role of targeted therapies. Prostate-specific membrane antigen (PSMA)-targeted therapy resulted in a notable PSA decline. This case highlights the evolving treatment landscape for rare prostate cancers, integrating genetic insights for tailored interventions. In conclusion, squamous cell carcinoma (SCC) of the prostate is rare, emphasizing the imperative for enhanced comprehension in diagnosis and management. Our case suggests the potential efficacy of ARPI and PSMA-targeted therapies. Our findings advocate for a more nuanced approach to the management of this rare prostate cancer variant, leveraging genomic insights for personalized treatment strategies. This exploration serves as a foundation for further research and clinical considerations in addressing the challenges posed by mixed adenosquamous cell carcinoma of the prostate.

Gene Expression Analysis for Uterine Cervix and Corpus Cancer Characterization.

The analysis of gene expression quantification data is a powerful and widely used approach in cancer research. This work provides new insights into the transcriptomic changes that occur in healthy uterine tissue compared to those in cancerous tissues and explores the differences associated with uterine cancer localizations and histological subtypes. To achieve this, RNA-Seq data from the TCGA database were preprocessed and analyzed using the KnowSeq package. Firstly, a kNN model was applied to classify uterine cervix cancer, uterine corpus cancer, and healthy uterine samples. Through variable selection, a three-gene signature was identified (VWCE, CLDN15, ADCYAP1R1), achieving consistent 100% test accuracy across 20 repetitions of a 5-fold cross-validation. A supplementary similar analysis using miRNA-Seq data from the same samples identified an optimal two-gene miRNA-coding signature potentially regulating the three-gene signature previously mentioned, which attained optimal classification performance with an 82% F1-macro score. Subsequently, a kNN model was implemented for the classification of cervical cancer samples into their two main histological subtypes (adenocarcinoma and squamous cell carcinoma). A uni-gene signature (ICA1L) was identified, achieving 100% test accuracy through 20 repetitions of a 5-fold cross-validation and externally validated through the CGCI program. Finally, an examination of six cervical adenosquamous carcinoma (mixed) samples revealed a pattern where the gene expression value in the mixed class aligned closer to the histological subtype with lower expression, prompting a reconsideration of the diagnosis for these mixed samples. In summary, this study provides valuable insights into the molecular mechanisms of uterine cervix and corpus cancers. The newly identified gene signatures demonstrate robust predictive capabilities, guiding future research in cancer diagnosis and treatment methodologies.

Adenosquamous carcinoma of the vulva: Rare tumor with unusual clinical presentation.

A 52-year-old female presented with labial ulcer of 4-month duration. Examination showed 1 cm × 1 cm single superficial ulcer in the right labium majus. Excision was done, and histopathologic examination revealed surface ulceration and dermal invasion by epithelial neoplasm formed of biphasic proliferation of squamoid and gland-forming cells. Immunohistochemical staining with p63 showed nuclear staining of the squamoid nests and was negative in areas with glandular differentiation, while epithelial membrane antigen and carcinoembryonic antigen highlighted the glandular elements. The case was diagnosed as primary cutaneous adenosquamous carcinoma (ASC). ASC is an uncommon malignant cutaneous neoplasm that is more aggressive than conventional squamous cell carcinoma. There are a few reports of ASC that presented as an erythematous papule or plaque with a preference for the head, neck, or upper extremities. We report a novel case of vulval ASC presented as a superficial ulcer, which is considered a unique site, and its clinical presentation.

Clinicopathological and molecular characteristics of colorectal adenosquamous carcinoma in an Asian population.

BACKGROUND: Adenosquamous carcinoma is a rare sub-type of colorectal cancer with a poor prognosis. Little is known about its clinicopathological and molecular characteristics in Asian populations. This study aimed to investigate these features in a cohort of patients with adenosquamous carcinoma in the colorectum. METHODS: Tumor cases pathologically diagnosed with colorectal adenosquamous carcinoma were retrieved from the Sixth Affiliated Hospital, Sun Yat-sen University tissue archive between December 2012 and June 2020. Clinicopathological features, molecular characteristics, and oncology outcomes were analyzed. RESULTS: Among 18,139 cases of colorectal cancer, 11 were diagnosed with adenosquamous carcinoma, providing an incidence rate of 0.061%. The median overall survival (OS) was 14 months, and the expected 3-year OS rate was 29.6%. As of October 14, 2022, four cases had local recurrence and five had distant metastasis. KRAS gene mutations were found in four of seven patients (57.1%), and three out of eleven (27.3%) patients had mismatch repair-deficient (dMMR) tumors. CONCLUSIONS: Adenosquamous carcinoma is associated with a poor prognosis. Compared to other sub-types of colorectal cancer, a higher proportion of patients with dMMR and KRAS mutations were observed. These findings suggested that more patients with adenosquamous carcinoma could benefit from targeted therapies, such as immunotherapy.

Intratumoral and peritumoral MRI radiomics nomogram for predicting parametrial invasion in patients with early-stage cervical adenocarcinoma and adenosquamous carcinoma.

OBJECTIVE: To develop a comprehensive nomogram based on MRI intra- and peritumoral radiomics signatures and independent risk factors for predicting parametrial invasion (PMI) in patients with early-stage cervical adenocarcinoma (AC) and adenosquamous carcinoma (ASC). METHODS: A total of 460 patients with IB to IIB cervical AC and ASC who underwent preoperative MRI examination and radical trachelectomy/hysterectomy were retrospectively enrolled and divided into primary, internal validation, and external validation cohorts. The original (Ori) and wavelet (Wav)-transform features were extracted from the volumetric region of interest of the tumour (ROI-T) and 3mm- and 5mm-peritumoral rings (ROI-3 and ROI-5), respectively. Then the Ori and Ori-Wav feature-based radiomics signatures from the tumour (RST) and 3 mm- and 5 mm-peritumoral regions (RS3 and RS5) were independently built and their diagnostic performances were compared to select the optimal ones. Finally, the nomogram was developed by integrating optimal intra- and peritumoral signatures and clinical independent risk factors based on multivariable logistic regression analysis. RESULTS: FIGO stage, disruption of the cervical stromal ring on MRI (DCSRMR), parametrial invasion on MRI (PMIMR), and serum CA-125 were identified as independent risk factors. The nomogram constructed by integrating independent risk factors, Ori-Wav feature-based RST, and RS5 yielded AUCs of 0.874 (0.810-0.922), 0.885 (0.834-0.924), and 0.966 (0.887-0.995) for predicting PMI in the primary, internal and external validation cohorts, respectively. Furthermore, the nomogram was superior to radiomics signatures and clinical model for predicting PMI in three cohorts. CONCLUSION: The nomogram can preoperatively, accurately, and noninvasively predict PMI in patients with early-stage cervical AC and ASC. CLINICAL RELEVANCE STATEMENT: The nomogram can preoperatively, accurately, and noninvasively predict PMI and facilitate precise treatment decisions regarding chemoradiotherapy or radical hysterectomy in patients with early-stage cervical AC and ASC. KEY POINTS: The accurate preoperative prediction of PMI in early-stage cervical AC and ASC can facilitate precise treatment decisions regarding chemoradiotherapy or radical hysterectomy. The nomogram integrating independent risk factors, Ori-Wav feature-based RST, and RS5 can preoperatively, accurately, and noninvasively predict PMI in early-stage cervical AC and ASC. The nomogram was superior to radiomics signatures and clinical model for predicting PMI in early-stage cervical AC and ASC.

Two Head and Neck Carcinomas With Squamous and Mucinous Components and Human Papillomavirus Associations: Maxillary Mucoepidermoid Carcinoma ex Sinonasal Schneiderian Papilloma and Tonsillar Invasive Stratified Mucin Producing Carcinoma (ISMC).

Carcinomas of the head-and-neck region with squamous and glandular/mucinous features constitute a heterogeneous group, with a significant minority of tumors showing an human papillomavirus (HPV) association. The differential diagnosis is usually between mucoepidermoid carcinoma (MEC) and adenosquamous carcinoma. We present here two tumors that exemplify both the challenges of diagnostic classification, as well as the complex relationship to HPV: (a) a low risk HPV positive/p16 negative carcinoma that is most consistent with a relatively typical intermediate grade mucoepidermoid type carcinoma with complete MEC phenotype (three cell types), originating from intranasal sinonasal papillomas with exophytic and inverted patterns, and invading surrounding maxillary compartments, and (b) a p16 and keratin 7 (KRT7) positive carcinoma of the right tonsil, characterized by stratified squamous and mucinous cell (mucocyte) features. Whereas the first tumor represents a typical MEC ex-Schneiderian papilloma, the second is morphologically most consistent with the, novel for this anatomic location, diagnosis of "invasive stratified mucin producing carcinoma" (ISMC), pointing to an analogy to similar, high-risk HPV-driven malignancies recently described in the gynecologic (GYN) and genitourinary (GU) areas. Both tumors, despite their mucoepidermoid-like features had no connection to salivary glands and lacked the MAML2 translocation typical of salivary gland MEC, pointing to a mucosal/non-salivary gland origin. Using these two carcinomas as examples, we attempt to address questions related to: (a) the histological distinction between MEC, adenosquamous carcinoma, and ISMC, (b) similarities and differences between these histological entities in mucosal sites versus morphologically similar salivary gland tumors, and (c) the role of HPV in these tumors.

Deep Learning Nomogram for the Identification of Deep Stromal Invasion in Patients With Early-Stage Cervical Adenocarcinoma and Adenosquamous Carcinoma: A Multicenter Study.

BACKGROUND: Deep stromal invasion (DSI) is one of the predominant risk factors that determined the types of radical hysterectomy (RH). Thus, the accurate assessment of DSI in cervical adenocarcinoma (AC)/adenosquamous carcinoma (ASC) can facilitate optimal therapy decision. PURPOSE: To develop a nomogram to identify DSI in cervical AC/ASC. STUDY TYPE: Retrospective. POPULATION: Six hundred and fifty patients (mean age of 48.2 years) were collected from center 1 (primary cohort, 536), centers 2 and 3 (external validation cohorts 1 and 2, 62 and 52). FIELD STRENGTH/SEQUENCE: 5-T, T2-weighted imaging (T2WI, SE/FSE), diffusion-weighted imaging (DWI, EPI), and contrast-enhanced T1-weighted imaging (CE-T1WI, VIBE/LAVA). ASSESSMENT: The DSI was defined as the outer 1/3 stromal invasion on pathology. The region of interest (ROI) contained the tumor and 3 mm peritumoral area. The ROIs of T2WI, DWI, and CE-T1WI were separately imported into Resnet18 to calculate the DL scores (TDS, DDS, and CDS). The clinical characteristics were retrieved from medical records or MRI data assessment. The clinical model and nomogram were constructed by integrating clinical independent risk factors only and further combining DL scores based on primary cohort and were validated in two external validation cohorts. STATISTICAL TESTS: Student's t-test, Mann-Whitney U test, or Chi-squared test were used to compare differences in continuous or categorical variables between DSI-positive and DSI-negative groups. DeLong test was used to compare AU-ROC values of DL scores, clinical model, and nomogram. RESULTS: The nomogram integrating menopause, disruption of cervical stromal ring (DCSRMR), DDS, and TDS achieved AU-ROCs of 0.933, 0.807, and 0.817 in evaluating DSI in primary and external validation cohorts. The nomogram had superior diagnostic ability to clinical model and DL scores in primary cohort (all P < 0.0125 [0.05/4]) and CDS (P = 0.009) in external validation cohort 2. DATA CONCLUSION: The nomogram achieved good performance for evaluating DSI in cervical AC/ASC. LEVEL OF EVIDENCE: 3 TECHNICAL EFFICACY: Stage 2.

Primary Adenosquamous Carcinoma of the Prostate With Multiple Heterogenic Metastases Demonstrated on 68 Ga-PSMA and 18 F-FDG PET/CT Imaging.

ABSTRACT: A 54-year-old man presented with a 2-month history of urination disturbances. Serum prostate-specific antigen level was 4.96 ng/mL, and a possibility of benign prostate hyperplasia was raised by outside medical CT. Histopathology revealed adenosquamous carcinoma. Staging workup showed large areas of high PSMA uptake and focal intense hypermetabolism in the prostate, multiple lymphatics, bone, and pulmonary heterogenic metastases on 68 Ga-PSMA and 18 F-FDG PET/CT imaging.

Initial treatment for FIGO 2018 stage IIIC cervical cancer based on histological type: A 14-year multicenter study.

BACKGROUND: To compare the oncological outcomes of radical chemotherapy (R-CT), abdominal radical hysterectomy (ARH), and neoadjuvant chemotherapy and radical surgery (NACT) for International Federation of Gynecology and Obstetrics (FIGO) 2018 stage IIIC cervical cancer, according to histological types: squamous cell carcinoma (SCC) and adenocarcinoma (AC)/adenosquamous cell carcinoma (ASC). METHODS: A comparison of 5-year overall survival (OS) and disease-free survival (DFS) was performed for the SCC and AC/ASC subgroups for the three initial treatments, assessed using Kaplan-Meier and Cox proportional hazards regression analysis and validated using propensity score matching (PSM). RESULTS: The study included 4086 patients: R-CT, n = 1913; ARH, n = 1529; and NACT, n = 644. AC/ASC had a lower survival rate (63.7%) than SCC (73.6%) and a higher recurrence and mortality rate (36.3% and 26.4%, respectively). The 5-year OS and DFS rates were different in the SCC group for R-CT, ARH, and NACT (OS: 69.8% vs. 80.8% vs. 73.0%, p < 0.001; DFS: 66.7% vs. 70.7% vs. 56.4%, p < 0.001), also in the AC/ASC group (OS: 46.1% vs. 70.6% vs. 55.6%, p < 0.001; DFS: 42.7% vs. 64.6% vs. 40.8%, p < 0.001). As for initial treatment, survival outcomes were worse for AC/ASC treated with R-CT and ARH than for SCC (both p < 0.05), with no group differences between the two treated with NACT. CONCLUSION: Initial treatment influences oncological prognosis for patients with FIGO 2018 stage IIIC cervical cancer. ARH is an alternative treatment for stage IIIC cervical SCC and AC/ASC, and NACT needs to be chosen with caution, moreover, R-CT for AC/ASC requires careful selection.

A case of discordant histology and expression of programmed death ligand 1 between primary tumor and brain metastases in adenosquamous carcinoma of the lung.

A patient presented with vomiting and gait disturbance. Investigation revealed a single cerebellar tumor and another tumor in the upper lobe of the left lung. Based on the severe vomiting and gait disturbance, we removed the cerebellar tumor first, achieving resolution of symptoms. The cerebellar tumor was pathologically diagnosed as metastatic lung adenocarcinoma. No other metastases were identified, including in the mediastinal lymph nodes. We therefore resected the primary lung tumor. On final pathological analysis, the tumor in the upper lobe of the left lung was diagnosed as adenosquamous carcinoma with no lymph node metastasis. PD-L1 expression was low in the primary lung adenosquamous carcinoma and high in the cerebellar metastasis. Furthermore, both tumors were KRASG12C -positive. Tumor PD-L1 expression is considered important for immune escape. In this case, adenocarcinoma cells in the primary adenosquamous carcinoma may have migrated to form a cerebellar metastasis. In advanced lung cancer, tumor growth may be observed in some lesions even when many other lesions are controlled by chemo- or immunotherapy. Biopsy to confirm histology and PD-L1 expression is worth considering, depending on the location of the metastases and the invasiveness of the biopsy procedure.

Genetic analysis of low-grade adenosquamous carcinoma of the breast progressing to high-grade metaplastic carcinoma.

PURPOSE: Low-grade adenosquamous carcinoma (LGASC) is a rare type of metaplastic carcinoma of the breast (MBC) with an indolent clinical course. A few LGASC cases with high-grade transformation have been reported; however, the genetics underlying malignant progression of LGASC remain unclear. METHODS: We performed whole-genome sequencing analysis on five MBCs from four patients, including one case with matching primary LGASC and a lymph node metastatic tumor consisting of high-grade MBC with a predominant metaplastic squamous cell carcinoma component (MSC) that progressed from LGASC and three cases of independent de novo MSC. RESULTS: Unlike de novo MSC, LGASC and its associated MSC showed no TP53 mutation and tended to contain fewer structural variants than de novo MSC. Both LGASC and its associated MSC harbored the common GNAS c.C2530T:p.Arg844Cys mutation, which was more frequently detected in the cancer cell fraction of MSC. MSC associated with LGASC showed additional pathogenic deletions of multiple tumor-suppressor genes, such as KMT2D and BTG1. Copy number analysis revealed potential 18q loss of heterozygosity in both LGASC and associated MSC. The frequency of SMAD4::DCC fusion due to deletions increased with progression to MSC; however, chimeric proteins were not detected. SMAD4 protein expression was already decreased at the LGASC stage due to unknown mechanisms. CONCLUSION: Not only LGASC but also its associated high-grade MBC may be genetically different from de novo high-grade MBC. Progression from LGASC to high-grade MBC may involve the concentration of driver mutations caused by clonal selection and inactivation of tumor-suppressor genes.

Adenosquamous proliferation in radial sclerosing lesions: Histologic spectrum and key features in systematic review of 247 lesions.

Adenosquamous proliferation (ASP) is known to occur in the central nidus of radial sclerosing lesions (RSL) of the breast. However, their significance is debated and remains largely unknown. In addition, there is a histologic overlap between ASP and low-grade adenosquamous carcinomas (LGASC). We conducted a large retrospective review of 247 RSLs to evaluate the prevalence of ASP and quantitatively analyze associated histologic features of RSLs including size, stromal cellularity, and presence of chronic inflammation. The central nidus of RSLs were classified as hyalinized in 121 cases (49%), cellular in 37 cases (15%), and equally mixed hyalinized and cellular in 89 (36%). ASP occurred in 92 of 247 RSLs (37.2%). Cases with ASP were significantly associated with a cellular stroma; 78.4% of RSLS with cellular stroma had ASP versus just 11.6% of hyalinized RSLs. In our large cohort, inflammation is commonly found in RSLs with ASP (p= <0.001). In conclusion, we confirm that ASP is statistically more likely to be found in RSLs with a cellular stroma. In addition, ASP is commonly associated with chronic inflammation. The finding challenges the notion that prominent lymphocytes are a diagnostic clue to LGASC on limited biopsy material.

Adenosquamous carcinoma of the gallbladder simultaneously producing granulocyte-colony-stimulating factor and parathyroid hormone-related protein.

We report a rare case of adenosquamous carcinoma of the gallbladder which simultaneously produces granulocyte-colony-stimulating factor (G-CSF) and parathyroid hormone-related protein (PTHrP), confirmed serologically and histologically. A 71-year-old man was examined for a gallbladder tumor with multiple lymph nodes and liver metastases. Histopathological evaluation by endoscopic ultrasound fine-needle aspiration revealed adenosquamous carcinoma of the gallbladder. Laboratory data showed markedly elevated white blood cell (WBC) count of 34,700 µL and corrected serum calcium level of 14.9 mg/dL. Serum G-CSF (191 pg/mL) and PTHrP (23.1 pmol/L) levels were high. Zoledronic acid and calcitonin were administered to treat hypercalcemia, which normalized serum calcium levels. Gemcitabine-cisplatin chemotherapy was started for cStage IVB gallbladder cancer. After chemotherapy initiation, WBCs showed a rapid downward trend; however, the patient suddenly developed acute respiratory distress syndrome; thus, chemotherapy was discontinued. Subsequently, WBC count increased again, and the patient's overall condition deteriorated. The patient died on day 27. Immunohistochemistry using autopsy specimens demonstrated patchy staining for G-CSF in the squamous cell carcinoma portion and diffuse and weak positive staining for PTHrP in the squamous cell carcinoma and poorly differentiated adenocarcinoma portions of the tumor, suggesting simultaneous G-CSF and PTHrP production by the tumor. This is the first report of a patient with gallbladder cancer with serological and histological evidence for G-CSF and PTHrP production.

Adenosquamous carcinoma lung radiologically mimicking pneumonia: A potentially disastrous diagnostic challenge in an unusual malignancy.

Lung cancer is among the most frequently diagnosed cancers and the world's leading cause of cancer-related death. Radiology remains the mainstay for timely diagnosis; however, atypical radiologic patterns are known, and these may be misdiagnosed as infectious or inflammatory pathology, particularly in the absence of smoking history. We report herein an account of an older male nonsmoker who presented radiologically with bilateral diffuse pulmonary infiltrates, simulating pneumonia, but was eventually diagnosed with adenosquamous lung carcinoma. The delay in diagnosis and subsequent unfortunate rapid deterioration of our patient serves as a reminder for clinicians to consider lung cancer in patients with clinical/radiologic findings suggestive of pneumonia, especially in nonsmokers or cases refractory to antibiotic therapy.

EGFR Expression in Gallbladder Carcinoma in North Indian Population.

OBJECTIVE: Gallbladder carcinoma is the most frequent biliary tract carcinoma with over all very poor prognosis. Epidermal growth factor receptor (EGFR) is known to be involved in carcinogenesis and overexpressed in various malignancies including head and neck, breast, lung and colon carcinomas. This study was done to explore the expression of EGFR in gallbladder carcinoma cases in the north Indian population so that it may be used as a therapeutic target in these patients. MATERIALS AND METHODS: 59 cases of gallbladder carcinoma diagnosed by histopathological examination were included in study. Expression of EGFR was seen by immunohistochemistry method on histopathology slides. RESULTS: Out of 59 gallbladder carcinoma cases 46 (78%) were female and 13 (22%) were male with female to male ratio of 3.54:1. Mean age was 51.71±11.32 years. On histopathological examination 51 (86.4%) cases were conventional adenocarcinoma, 2 (3.4%) adenosquamous carcinoma, 2 (3.4%) mucinous adenocarcinoma, 2 (3.4%) papillary adenocarcinoma, 1 (1.7%) signet ring cell carcinoma and 1 (1.7%) squamous cell carcinoma histological subtypes. EGFR expression was present in 31 (52.5%) of gallbladder carcinoma cases and strong EGFR expression was significantly associated with poor differentiation of tumour. CONCLUSION: In our study EGFR was positive in the majority of gallbladder carcinoma cases. There was inverse correlation between differentiation of tumor and EGFR expression. Strong EGFR expression was significantly higher in poorly differentiated tumors compared to well differentiated tumors suggesting its role in prognosis. This also suggest that EGFR might have a role in tumor progression and aggressiveness. Therefore, EGFR have potential to be used as therapeutic target in significant number of patients. More larger sample studies are required to confirm our findings. EGFR may be further studied as therapeutic target in clinical trials in the Indian population to improve morbidity and mortality of gallbladder carcinoma patients. KEY WORDS: EGFR Expression, Gallbladder Carcinoma, Immunohistochemistry, Targeted Therapy.

Adenosquamous carcinoma of the gallbladder: a rare entity and dilemmas in its management.

Gallbladder carcinomas are the most common form of biliary tract malignancies with adenocarcinomas, by far the most common variant while adenosquamous (adenosquamous carcinoma of the gallbladder) or pure squamous cell carcinomas representing only 2%-10% of all gallbladder carcinomas. Despite being a minority, these tumours demonstrate aggressive behaviour resulting in delayed presentations with widespread local invasion. We report a case involving a woman in her 50s who was diagnosed on imaging with a suspected gallbladder malignancy in the community. She proceeded to have a laparoscopic extended cholecystectomy with a cuff of segment 4b and 5 liver resection and cystic node sampling revealing a T3N1 lesion which on further recommendation by the multidisciplinary team proceeded to have an open portal lymphadenectomy yielding another positive lymph node. This case report highlights the dilemmas encountered in the management of this rare histological subtype in the absence of well-defined treatment algorithm and evolving guidelines.

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.