ABSTRACT
Differentiated high-grade thyroid carcinoma (DHGTC) has a high mitotic count (≥5 mitoses per 2mm2) and/or tumor necrosis without anaplastic features. These tumors are rare, and the prevalence is not yet established among thyroid malignancies. BRAF andRAS mutations are the main driver mutations in these tumors. We present a case of a 43-year-old woman with DHGTC and NRASmutation, presenting with metastatic follicular component to the bone and papillary component to lymph nodes.
ABSTRACT
Metaplastic breast carcinoma (MBC) represents a heterogeneous group of aggressive primary breast cancers that can show differentiation into carcinomatous and sarcomatous elements. Due to its rapid growth, this malignancy can replace precursor lesions, which remain unknown in most cases. Herein, we describe a MBC presenting as a deceptive post-biopsy hematoma. Histopathological and immunohistochemical evaluation of the primary tumor revealed a squamous cell carcinoma arising in a background of squamous metaplasia of lactiferous ducts (SMOLD). In the absence of ductal carcinoma in situ, we consider SMOLD as a nonobligatory precursor of MBC. The tumor showed 'dedifferentiation' into spindle, mucin-producing, osteoclast-like giant cell and fibromatosis-like carcinoma. Next-generation sequencing revealed the driver mutations HRASQ61R and PIK3R1c.1738_1745+2del in addition to MYH11S638L and amplification of ERCC5 and FGF14, which were potential contributors to tumor phenotype. Tumor dedifferentiation was probably facilitated by epithelial-to-mesenchymal transition (EMT) with aberrant expression of platelet and endothelial adhesion molecule-1, leading to early metastasis via hematogenous route rather than lymphatic. The co-occurrence of phosphoinositide 3-kinase and mitogen-activated protein kinase pathway abnormalities along with EMT could mediate divergent growth in breast cancer.
