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Context.--Lobular carcinoma in situ (LCIS) refers to a neoplastic proliferation of cells that characteristically shows loss of E-cadherin expression and has long been regarded as a risk factor for invasive breast cancer. Long-term outcome studies and molecular data have also implicated LCIS as a nonobligate precursor to invasive carcinoma. In the past few decades, pleomorphic and florid LCIS have been recognized as morphologic variants of LCIS with more-aggressive histopathologic features, less-favorable biomarker profiles, and more-complex molecular features compared with classic LCIS. There is still a lack of consensus regarding certain aspects of managing patients with LCIS. Objectives.--To review recently published literature on LCIS and to provide an overview of the current morphologic classification of LCIS, recent molecular advances, and trends in patient management. Data Sources.--Sources included peer-reviewed, published journal articles in PubMed (US National Library of Medicine, Bethesda, Maryland) and published guidelines from the National Comprehensive Cancer Network (Fort Washington, Pennsylvania). Conclusions.--Lobular carcinoma in situ represents a marker for increased risk of breast cancer, as well as a nonobligate precursor to invasive carcinoma. Morphologic variants of LCIS--florid and pleomorphic LCIS--are genetically more-complex lesions and are more likely to be associated with invasive carcinoma. Further investigation into which molecular alterations in LCIS are associated with progression to invasive carcinoma is needed to help guide medical and surgical management. (Arch Pathol Lab Med. 2017;141:1668-1678; doi: 10.5858/arpa.2016-0421-RA), Lobular carcinoma in situ (LCIS) was described by Foote and Stewart (1) more than 75 years ago as an in situ disease affecting multiple lobules and terminal ducts that is [...]

* Context.--Small glandular proliferations of the breast encompass a variety of benign, atypical, and malignant lesions that show some overlapping morphologic features. Myoepithelial stains are frequently used in the workup of these lesions in order to rule out or establish a diagnosis of invasive carcinoma. Some benign lesions show absent or diminished myoepithelial staining, and may represent an interpretative pitfall, particularly in small core biopsy samples. Objective.--To review small glandular proliferations of the breast that show absent or diminished staining with myoepithelial immunohistochemical markers. Data Sources.--The study comprised a review of published literature and clinical case material. Conclusions.--The interpretation of myoepithelial stains in small glandular proliferations of the breast can, on some occasions, represent a challenge in diagnosing these lesions. Recognition of the key histopathologic features and immunohistochemical staining patterns of the entities in the differential diagnosis is crucial in their workup. (Arch Pathol Lab Med. 2016;140:651-664; doi: 10.5858/arpa.2015-0289-SA), Small glandular proliferations of the breast encompass a variety of benign, atypical, and malignant lesions. These proliferations show some degree of morphologic overlap and making the distinction among them may [...]

Juvenile papillomatosis (JP) of the breast is a rare benign mass‐forming lesion occurring in young women, which is histologically characterized by a constellation of proliferative changes and large cysts, giving it the gross appearance of Swiss cheese. A subset of patients with JP report a family history of breast carcinoma and/or coexisting or subsequent breast carcinoma. We performed whole‐exome sequencing of the hyperplastic epithelial component of three JPs, including one with coexisting ductal carcinoma in situ (DCIS) and invasive ductal carcinoma of no special type (IDC‐NST). JPs harbored clonal somatic PIK3CA hotspot mutations in two cases. In the JP with coexisting DCIS and IDC‐NST, these lesions were clonally related to the associated JP, sharing a clonal PIK3CA E542K somatic hotspot mutation. JP showed a paucity of copy number alterations, whereas the associated DCIS and IDC‐NST showed concurrent 1q gains/16q losses, hallmarks of estrogen receptor (ER)‐positive breast cancers. We observed JP to harbor a dominant aging‐related mutational signature, whereas coexisting DCIS and IDC‐NST showed greater exposure to an APOBEC signature. Taken together, our findings suggest that, at least in a subset of cases, JP might constitute the substrate from which DCIS and invasive breast carcinomas develop. [ABSTRACT FROM AUTHOR]

* Context.--Lobular carcinoma in situ (LCIS) as the primary pathologic diagnosis in a needle core biopsy is an infrequent finding, and the management of patients in this setting is controversial. Objective.--To determine the rate of pathologic upgrade (defined as the presence of a clinically moresignificant lesion in the subsequent excision) in patients with a primary pathologic diagnosis of LCIS in the needle core biopsy. Design.--Patients with a primary diagnosis of LCIS in a needle core biopsy who underwent subsequent excision were identified. Core biopsies containing a concurrent high-risk lesion and cases with radiologic-pathologic discordance were excluded. The presence of selected microscopic features in the needle core biopsy was correlated with pathologic upgrade. Microscopic findings were correlated with the radiographic target in the needle core biopsy. Results.--Sixty-one women with primary LCIS in their needle core biopsy showed a 10% pathologic upgrade rate. The percentage of cores involved by LCIS was significantly associated with pathologic upgrade (P = .04), whereas the remaining measured parameters were not. When LCIS represented the radiographic target, the pathologic upgrade rate was 18%, whereas when it was an incidental finding, the pathologic upgrade rate was 4%. Conclusions.--It may be reasonable for patients with primary, yet incidental, LCIS on needle core biopsy to be managed in a nonsurgical fashion. Larger studies are needed to confirm our findings. (Arch Pathol Lab Med. 2013;137:927-935; doi: 10.5858/arpa.2012-0297-OA), Lobular carcinoma in situ (LCIS) and atypical lobular hyperplasia (ALH) are infrequent findings in needle core biopsy samples, occurring in approximately 0.5% to 4% of needle core biopsies. (1-10) Finding [...]

* Lipomas are commonly encountered benign mesenchymal neoplasms composed of adipocytes that arise in the superficial subcutaneous tissues of the extremities and trunk. Occasionally, these tumors can originate from either within muscle (intramuscular) or between muscles (intermuscular). The former typically occurs within skeletal muscle of large muscles of an extremity, such as the thigh and shoulder. Intramuscular lipomas arising specifically from the pectoralis muscle are exceedingly rare. In this report, to our knowledge we describe the second case of an intramuscular lipoma arising within the pectoralis muscle. Similar to the first published report, our patient's tumor was clinically thought to be a breast mass. However, this example is unique in that it is the first of its kind to be found incidentally during screening ultrasound. Intramuscular lipomas are not routinely included in the radiologic differential diagnosis of a breast mass. However, when the tumor is posteriorly located and appears to involve the pectoralis muscle, the diagnostic possibility of intramuscular lipoma should be entertained., Lipomas are commonly encountered benign mesenchymal neoplasms composed of adipocytes that arise in the superficial subcutaneous tissues of the extremities and trunk. Occasionally, these tumors can originate from either within [...]

The article describes the case of a 34-year-old woman with stage IV triple-positive breast cancer and elevated serum Beta Human Chorionic Gonadotropin (BhGC). Topics discussed include common diagnostic dilemmas in the field of obstetrics and gynecology, the death of the patient from complications of metastatic breast cancer, and potential explanations for increased hCG.

Abstract: 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. [ABSTRACT FROM AUTHOR]

Subareolar sclerosing duct hyperplasia (SSDH) remains to be fully characterized nearly 20 years after initial description. Thirty-five SSDH cases diagnosed over a 16-year period (January 2000 to December 2015) were reviewed. All patients were female (mean age = 59 years, range = 18-80) who had presented with a unilateral solitary lesion (left 22, right 13) with a mean size of 1.3 cm (range = 0.4-3.0 cm), and showed florid and papillary epithelial hyperplasia with dense sclerosis without involvement of nipple or areolar epidermis. Significant lesions concurrent within SSDH included low-grade adenosquamous carcinoma (n = 1), ductal carcinoma in situ (DCIS; n = 1), lobular carcinoma in situ (LCIS; n = 1), and atypical ductal hyperplasia (ADH; n = 13). No case of SSDH recurred in a mean follow-up of 44 months (range = 6-189). Subsequent significant lesions occurred in 6 patients: DCIS (n = 3; ipsilateral 2, contralateral 1), ipsilateral ADH (n = 2), and ipsilateral atypical lobular hyperplasia (n = 1). Long-term follow-up for patients with SSDH is indicated as DCIS can occur subsequently in either breast. [ABSTRACT FROM AUTHOR]

Thanatosomes, a form of degenerative intracellular hyaline globules, have been described in various neoplastic and nonneoplastic disease processes in several organs. These structures are indicative of apoptotic cell death. Herein, we report 2 cases of malignant phylloides tumor, both of which showed numerous thanatosomes—to the point of dominating the histological appearance and masking the stromal element. Our subsequently conducted study showed that thanatosomes were present in 14 of 86 (16.3%) high-grade malignant breast tumors. The structures were identified in 5/25 (20%) malignant phylloides tumors, 4/19 (21.1%) metaplastic spindle cell carcinomas, 3/21 (14.3%) invasive carcinomas s/p neoadjuvant chemotherapy, and 2/21 (9.5%) poorly differentiated invasive ductal carcinomas. When present, thanatosomes were typically a rare and focal finding in most types of cases. In malignant phylloides tumors, the structures were relatively more numerous when present. Our study shows that although thanatosomes can be present in several types of malignant breast tumors, they are more common in malignant phylloides tumor. Only rarely, as evident from our 2 index cases, do thanatosomes cause diagnostic difficulty. [ABSTRACT FROM AUTHOR]