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The tumor microenvironment regulates tissue development and homeostasis, and its dysregulation contributes to neoplastic progression. Increased expression of type X collagen α‐1 (ColXα1) in tumor‐associated stroma correlates with poor pathologic response to neoadjuvant chemotherapy in estrogen receptor (ER) and human epidermal growth factor receptor 2 (HER2)‐positive breast cancers. Evaluation of ColXα1 expression patterns suggests a potential connection with elastin fibers. To investigate the possible interaction between ColXα1 and elastin, we evaluated the expression of ColXα1 in relation to elastin fibers in normal breast tissue, ductal carcinoma in situ, and invasive breast carcinomas at cellular and subcellular levels. Our findings demonstrate that ColXα1 colocalizes with elastin in invasive breast cancer‐associated stroma by immunohistochemistry, immunofluorescence, and electron microscopy. In 212 invasive breast carcinomas, this complex was aberrantly and selectively expressed in tumor extracellular matrix in 79% of ER+/HER2−, 80% of ER+/HER2+, 76% of ER−/HER2+, and 58% of triple negative breast cancers. In contrast, ColXα1 was generally absent, while elastin was present perivascularly in normal breast tissue. ColXα1 and elastin were coexpressed in 58% of ductal carcinoma in situ (DCIS) in periductal areas. In mass‐forming DCIS with desmoplastic stroma, the complex was intensely expressed in periductal areas as well as within the tumor‐associated stroma in all cases. Our data suggest that the breast carcinoma neoplastic process may involve aberrant expression of ColXα1 and elastin in the tumor microenvironment emerging early at the DCIS stage. Enrichment of these complexes in tumor‐associated stroma may represent a stromal signature indicative of intrinsic differences between breast cancers. These findings shed light on investigation into the role of aberrant collagen complex expression in tumorigenesis and tumor progression which may be leveraged in therapeutic and theranostic applications. [ABSTRACT FROM AUTHOR]

Primary hyperparathyroidism ( PHPT) is one of the most common of all endocrine disorders encountered by the practising histopathologist. The vast majority of lesions are sporadic in nature, approximately 85% of which are parathyroid adenomas, while hyperplasia and carcinoma account for 10-15% and fewer than 1%, of cases, respectively. Heritable forms of PHPT are much less common and present challenges both to clinicians and pathologists, particularly when they are the presenting feature of an endocrine syndrome. In such instances, pathologists play a key role in alerting physicians to the possibility of an underlying heritable endocrine syndrome and the potential for extra-endocrine manifestations. Therefore, a working knowledge of these disorders is essential for providing guidance to treating physicians. The aim of this update is to review the clinicopathological features, genetic bases and current management for patients with PHPT associated with multiple endocrine neoplasia ( MEN) types 1, 2A and 4 and hyperparathyroidism-jaw tumour ( HPT- JT) syndrome in the context of the 2017 World Health Organization ( WHO) Classification of Tumours of the Endocrine Organs. Additionally, familial isolated hyperparathyroidism, familial hypocalciuric hypercalcaemia and neonatal severe hyperparathyroidism are discussed. [ABSTRACT FROM AUTHOR]