Faculty Bibliography

Mucinous lesions of the breast include a variety of benign and malignant epithelial processes that display intracytoplasmic or extracellular mucin, including mucocele-like lesions, mucinous carcinoma, solid papillary carcinoma, and other rare subtypes of mucin-producing carcinoma. The finding of free-floating or stromal mucin accumulations is a diagnostic challenge of which the significance depends on the clinical, radiologic, and pathologic context. This article emphasizes the differential diagnosis between benign and malignant mucin-producing lesions, with a brief consideration of potential mimics, such as biphasic and mesenchymal lesions with associated with mucinous, myxoid, or matrix material.

Metastasis causes ~90% of breast cancer mortality. However, standard prognostic tests based mostly on proliferation genes do not measure metastatic potential. Tumor MicroEnvironment of Metastasis (TMEM), an immunohistochemical biomarker for doorways on blood vessels that support tumor cell dissemination is prognostic for metastatic outcome in breast cancer patients. Studies quantifying TMEM doorways have involved manual scoring by pathologists utilizing static digital microscopy: a labor-intensive process unsuitable for use in clinical practice. We report here a validation study evaluating a new quantitative digital pathology (QDP) tool (TMEM-DP) for identification and quantification of TMEM doorways that closely mimics pathologists' workflow and reduces pathologists' variability to levels suitable for use in a clinical setting. Blinded to outcome, QDP was applied to a nested case-control study consisting of 259 matched case-control pairs. Sixty subjects of these were manually scored by five pathologists, digitally recorded using whole slide imaging (WSI), and then used for algorithm development and optimization. Validation was performed on the remainder of the cohort. TMEM-DP shows excellent reproducibility and concordance and reduces pathologist time from ~60 min to ~5 min per case. Concordance between manual scoring and TMEM-DP was found to be >0.79. These results show that TMEM-DP is capable of accurately identifying and scoring TMEM doorways (also known as MetaSite score) equivalent to pathologists.

Neuroendocrine neoplasms (NENs) are clinically diverse and incompletely characterized cancers that are challenging to classify. MicroRNAs (miRNAs) are small regulatory RNAs that can be used to classify cancers. Recently, a morphology-based classification framework for evaluating NENs from different anatomical sites was proposed by experts, with the requirement of improved molecular data integration. Here, we compiled 378 miRNA expression profiles to examine NEN classification through comprehensive miRNA profiling and data mining. Following data preprocessing, our final study cohort included 221 NEN and 114 non-NEN samples, representing 15 NEN pathological types and 5 site-matched non-NEN control groups. Unsupervised hierarchical clustering of miRNA expression profiles clearly separated NENs from non-NENs. Comparative analyses showed that miR-375 and miR-7 expression is substantially higher in NEN cases than non-NEN controls. Correlation analyses showed that NENs from diverse anatomical sites have convergent miRNA expression programs, likely reflecting morphological and functional similarities. Using machine learning approaches, we identified 17 miRNAs to discriminate 15 NEN pathological types and subsequently constructed a multilayer classifier, correctly identifying 217 (98%) of 221 samples and overturning one histological diagnosis. Through our research, we have identified common and type-specific miRNA tissue markers and constructed an accurate miRNA-based classifier, advancing our understanding of NEN diversity.

INTRODUCTION/BACKGROUND:Breast cystosarcoma phyllodes tumors are rare and can be benign or malignant. All sub-divisions of phyllodes tumor-benign, borderline and malignant, can harbor carcinomas, although the incidence is extremely rare. METHODS:We present two nonconsecutive cases of coexisting ductal carcinoma in situ (DCIS) and phyllodes breast tumors in young patients. METHODS & CASE PRESENTATION/UNASSIGNED:Retrospective review of two patient's medical record was performed. CASE 1: 30-year-old female underwent excisional biopsy for 3.48 cm mass found on ultrasound. Pathology revealed malignant phyllodes tumor with positive margin. On re-excision, patient was found to have 1.5 cm area of ductal carcinoma in situ (DCIS) with positive margin. Patient then underwent re-reexicision of DCIS with negative margin. Patient underwent chemotherapy and tamoxifen for three years without evidence of disease. CASE 2: 30-year-old female presented with 1.3 cm lesion found on ultrasound which core needle biopsy revealed a fibroepithelial tumor. Patient subsequently underwent excision biopsy which found 1.5 cm benign phyllodes tumor and 3.5 mm DCIS within the phyllodes tumor with negative margins. Patient declined additional chemotherapy or hormonal therapy and is currently considering mastectomy. CONCLUSION/CONCLUSIONS:Phyllodes tumors are rare and ones with a coexisting carcinoma are even less frequently encountered. The treatment plan can change upon diagnosis of the carcinoma via the pathology. Treatment should be guided by the type and stage of carcinoma detected which may include additional surgical resection and lymph node sampling.

AIMS/OBJECTIVE:Mammary angiomatosis is a rare, benign vascular lesion that morphologically mimics low-grade angiosarcoma (LGAS). To date, only occasional reports of this entity have been published, none of which included analysis by immunohistochemistry. The purpose of this study was to further characterise mammary angiomatosis by clinical, histological, and immunohistochemical means while emphasising distinguishing features from LGAS. METHODS:Seven cases of primary mammary angiomatosis were evaluated. For one patient, a subsequent recurrence was also evaluated. RESULTS:All patients were female with a median age at presentation of 51 years (range: 19-58 years). The most common clinical presentation was that of a palpable abnormality or mass (5/8) and the median primary tumour size was 3.1 cm (range: 2-9 cm). Of the six patients with follow-up, one developed a recurrence 6 years after initial presentation. Histologically, all cases were composed of variably sized ectatic, thin-walled vessels lined by flat normochromic endothelium diffusely infiltrating mammary stroma. Where present, lesional vessels infiltrated between and around terminal duct lobular units but not into individual intralobular stroma. Most cases (6/8) showed a combination of lymphatic-appearing and haemangiomatous-appearing vessels. Lymphatic-appearing vessels were D2-40 positive in all but one case. D2-40 was negative or weak in haemangiomatous-appearing vessels. All lesional vessels were CD31 positive. Ki-67 indices were <1% in all but one case (5%). CONCLUSIONS:Mammary angiomatosis is a rare vascular lesion that shares clinical, morphological and immunohistochemical features with LGAS; however, certain key traits make the distinction possible.

Cancer cells metastasize from primary tumors to regional lymph nodes and distant sites via the lymphatic and blood vascular systems, respectively. Our prior work has demonstrated that in primary breast tumors, cancer cells utilize a three-cell complex (known as tumor microenvironment of metastasis, or TMEM) composed of a perivascular macrophage, a tumor cell expressing high levels of the actin-regulatory protein mammalian enabled (Mena), and an endothelial cell as functional "doorways" for hematogenous dissemination. Here, we studied a well-annotated case-control cohort of human invasive ductal carcinoma of the breast and metastatic lymph nodes from a separate breast cancer cohort. We demonstrate that in primary breast tumors, blood vessels are always present within tumor cell nests (TCNs) and tumor-associated stroma (TAS), while lymphatic vessels are only occasionally present in TCN and TAS. Furthermore, TMEM doorways not only exist in primary tumors as previously reported but also in lymph node metastases. In addition, we show that TMEM intravasation doorways are restricted to the blood vascular endothelium in both primary tumors and lymph node metastases, suggesting that breast cancer dissemination to distant sites from both primary tumors and metastatic foci in lymph nodes occurs hematogenously at TMEM doorways. TMEMs are very rarely detected at lymphatic vessels and do not confer clinical prognostic significance, indicating they are not participants in TMEM-associated hematogenous dissemination. These findings are consistent with recent observations that hematogenous dissemination from lymph nodes occurs via blood vessels.

Tumor-infiltrating lymphocytes (TILs) have emerged as prognostic in triple-negative breast cancer (TNBC). We aimed to assess the consistency of hotspot placement and TIL enumeration among multiple pathologists. Additionally, we assessed hotspot TIL count consistency by comparing hotspot counts in 3 separate locations within a single whole-tissue section. Anti-CD8 immunohistochemistry was performed on a representative section from 66 cases of primary TNBC, which were then scanned as whole-slide images. Quantification of the tissue area and combined stromal and intratumoral CD8+ TILs was performed using digital image analysis (DIA) within 2.2 mm-diameter circle hotspots. TIL counts were quantified as absolute counts and densities (absolute count/tissue area in micrometers²). For each case, 6 pathologists placed a single hotspot, defined as an area with the subjectively highest CD8+ immunoreactivity, within the tumor bed. Separately for each case, a single pathologist placed hotspots in 3 different locations within a single tumor section. Intraclass correlation coefficients (ICCs) were generated following TIL enumeration via DIA. ICCs for single hotspot placement by 6 pathologists were 0.96 for density and 0.97 for absolute counts, respectively. In 32% of cases (21/66), all the hotspots placed by the 6 pathologists were in the same location. When evaluating hotspots in 3 different locations within a tumor, the ICC was 0.95 for both density and absolute counts. Hotspot evaluation by DIA is a reproducible method for CD8+ TIL quantification, and the use of hotspots may reduce TIL count variation caused by intratumoral TIL heterogeneity.

The development of effective therapies against brain metastasis is currently hindered by limitations in our understanding of the molecular mechanisms driving it. Here we define the contributions of tumour-secreted exosomes to brain metastatic colonization and demonstrate that pre-conditioning the brain microenvironment with exosomes from brain metastatic cells enhances cancer cell outgrowth. Proteomic analysis identified cell migration-inducing and hyaluronan-binding protein (CEMIP) as elevated in exosomes from brain metastatic but not lung or bone metastatic cells. CEMIP depletion in tumour cells impaired brain metastasis, disrupting invasion and tumour cell association with the brain vasculature, phenotypes rescued by pre-conditioning the brain microenvironment with CEMIP⁺ exosomes. Moreover, uptake of CEMIP⁺ exosomes by brain endothelial and microglial cells induced endothelial cell branching and inflammation in the perivascular niche by upregulating the pro-inflammatory cytokines encoded by Ptgs2, Tnf and Ccl/Cxcl, known to promote brain vascular remodelling and metastasis. CEMIP was elevated in tumour tissues and exosomes from patients with brain metastasis and predicted brain metastasis progression and patient survival. Collectively, our findings suggest that targeting exosomal CEMIP could constitute a future avenue for the prevention and treatment of brain metastasis.