Faculty Bibliography

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.

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.

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.

We present the case of a 73-year-old woman with an epithelial-myoepithelial carcinoma of the left breast (ie, malignant adenomyoepithelioma). In both the initial needle core biopsy and in the subsequently performed lumpectomy, the tumor consisted of nests of neoplastic epithelium and myoepithelium with cytologic atypia, increased mitoses, and infiltrative growth into the surrounding tissue. Mutational analysis showed oncogenic driver mutations in HRAS and PIK3CA. In this article, we describe an epithelial-myoepithelial carcinoma of the breast with focal metaplastic differentiation, an extremely rare entity, and report the results of targeted next-generation sequencing. Our patient has not shown any evidence of recurrent or metastatic disease at 29 months follow-up.

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.

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.

BACKGROUND:TIL enumeration. METHODS:TIL enumeration in prognosticating TNBC using immunohistochemistry on whole tissue sections and quantification by digital image analysis (Halo imaging analysis software; Indica Labs, Corrales, NM). A wide range of clinically relevant hot spot sizes was evaluated. RESULTS:TIL enumeration did not (P > .05). Statistical significance was not demonstrated when comparing between hot spots and whole-tumor annotations, as the groups had overlapping confidence intervals. CONCLUSION:TIL hot spot enumeration is equivalent to whole-tumor enumeration for prognostication in TNBC and may serve as a good alternative methodology in future studies and clinical practice.

Mammary myofibroblastoma is a benign spindle cell tumor that can show variable morphologic patterns and lines of differentiation. Diffuse and strong immunohistochemical expression of CD34 is a characteristic of myofibroblastoma and greatly aids in confirming a diagnosis. Myofibroblastoma has been shown to belong to a family of CD34-positive tumors with similar morphology that show a deletion of 13q14, which includes RB1 and FOXO1A genes. The purpose of this study was to better understand a subset of myofibroblastomas that is characteristically CD34-deficient by immunohistochemistry. Six myofibroblastomas were studied by immunohistochemistry and fluorescence in situ hybridization (FISH) for RB1. Patients included five women and one man, aged 41-85 years (median, 52.5). Tumor size ranged from 0.4 to 1.5 cm (mean, 0.95). Tumors showed spindle cell morphology in five cases and epithelioid features in one case. Two tumors showed complete lack of CD34 staining. The remaining showed weak focal or weak patchy CD34 staining. Dichotomous staining was seen in one case with CD34-positive spindle cell areas and CD34-negative myxoid areas. All six tumors showed ER expression, five of six showed desmin expression, and four of six showed bcl-2 positivity. Two of six (33.3%) tumors showed deletion of RB1 by FISH, including one that showed loss of Rb immunohistochemical staining. Myofibroblastomas uncommonly show absent/focal expression of CD34, a potential diagnostic pitfall, particularly in small samples. Characteristic staining with other immunohistochemical markers is seen which can aid in confirming the diagnosis. These tumors may harbor deletion of RB1, similar to CD34-positive myofibroblastomas, and this deletion may not correlate with loss of Rb by immunohistochemistry.