Intrathyroidal thymic carcinoma exhibiting neuroendocrine differentiation: Case report with cytomorphology, immunocytochemistry, and review of the literature focusing on cytology

The basaloid-spectrum of salivary gland tumors: A focused review with practical diagnostic considerations

Basaloid salivary gland neoplasms are a diverse and varied group of benign and malignant tumors. The term 'basaloid' is broadly used in reference to cells with elevated nuclear to cytoplasmic ratio, sparse cytoplasm, and hyperchromatic nuclei. However, a subset may also fit within the "small round blue cell tumor" morphologic category or the "biphasic" salivary gland tumor category. Furthermore, there are no established thresholds for the proportion of basaloid tumor cells needed to consider a tumor within the basaloid spectrum. Given the implicit variability in what is considered a basaloid salivary gland tumor, one may question the inclusion of certain entities (canalicular adenoma, HMGA2::WIF1 pleomorphic adenoma, polymorphous adenocarcinoma) in this review based on classic morphologic features. However, salivary gland tumors with even minor basaloid components may appear 'basaloid' in small biopsy specimens and, thus, a choice was made to focus on common and uncommon diagnostic differentials with this in mind. Entities that will be covered in this review also include basal cell adenoma and basal cell adenocarcinoma, adenoid cystic carcinoma, lymphoepithelial carcinoma, sialoblastoma, adamantinoma-like Ewing Sarcoma, NUT carcinoma, and carcinoma showing thymus-like differentiation.

Case Reports: A role of postoperative radiation therapy in completely resected early stage intrathyroid thymic carcinoma: a case report and literature review of the diagnosis and treatment

Background

Intrathyroid thymic carcinoma (ITTC) is a rare malignant tumor of the thyroid, probably arising from ectopic thymus or branchial pouch remnants. Most of the literature recommended radical resection as the fundamental treatment for ITTC, and postoperative radiation appears to be able to reduce the recurrence rate in patients with advanced ITTC. However, the issue of adjuvant radiotherapy in completely resected early-stage ITTC has been controversial.

Case presentation

Here, we reported a new case of early-stage ITTC that treated with total thyroidectomy and the right central neck dissection. Postoperative external beam radiation therapy (50.0 Gy/25 fractions) was given to the thyroid bed and bilateral cervical lymph node area since the tumor involved part of the sternal thyroid muscle. At 4-year follow-up after completion of radiotherapy, she is without evidence of locally recurrent or distant disease.

Conclusion

Since there are no current guidelines for early-stage ITTC, in combination with this case and previous literature, we may suggest routine adjuvant radiotherapy should be considered in patients with incompletely resected tumors and extraparenchymal extension of ITTC. Moreover, we summarized comprehensive and advanced diagnosis, treatment, prognosis of ITTC and comparison between ITTC, primary squamous cell carcinoma of thyroid gland, differentiated thyroid cancer, and anaplastic thyroid cancer.

Intrathyroidal thymic carcinoma not so indolent a neoplasm?

ABSTRACT

Intrathyroidal thymic carcinoma (ITC) is a very rare malignant epithelial tumor of the thyroid gland with thymic epithelial differentiation. Here, we are reporting the case of an eighty-year-old man who at presentation had extrathyroidal spread to the larynx and metastasis to regional lymph nodes. Though the tumor had a relatively low-grade morphology, there were areas of high mitotic activity with areas of necrosis. The classically described ivory-white gross appearance of the tumor, histomorphology of thick bands dividing the tumor into lobules, squamous cell differentiation, tight whorls of cells resembling Hassall's corpuscle, and areas showing dense lymphocytic infiltration, together with an immunoprofile of CD5, Ckit, Tumor protein 63 (p63), and B-cell lymphoma 2 gene (bcl2) positivity, helped in diagnosing this rare entity. Though classically ITC is said to have a good prognosis, cases with spread to adjacent organs and lymph node metastasis may not have an indolent course.

Intrathyroid thymic carcinoma: clinicopathological features and whole exome sequencing analysis

Intrathyroid thymic carcinoma (ITC) is a rare malignant tumour. We present nine cases of ITC that were analysed by immunohistochemical staining, of which five were analysed using whole exome sequencing (WES). These cases included six women and three men with an age range of 31-66 years. The average postoperative follow-up term was 37.8 months (range, 7-95 months), and all patients survived well except for one case with lung metastasis. Microscopically, ITC showed solid islands of tumour cells separated by fibrous connective tissue containing lymphocytes and other inflammatory cells. Tumour cells strongly expressed Ckpan (AE1/AE3), P63, and CD117. And all cases but one were positive for CD5. The median value of Ki-67 was 32% (range 10-60%). We observed partial positivity of Syn and CgA in only one case. ITC shares morphological and immunohistochemical similarities with thymic squamous cell carcinoma. In situ hybridization of EBER showed negative results. All cases were microsatellite stable, and the tumour mutational burden of the 5 cases was all < 1 mutations/Mb. WES showed higher mutation rates for N4BP1 (2/5), and many genetic alterations were related to the NF-kB signalling pathway, which is crucial for insight into the molecular mechanisms of the occurrence and development of ITC.

Neuroendocrine Tumors of the Thyroid and Their Mimics

This paper will review neuroendocrine lesions of the thyroid and the differential diagnosis with the most significant such tumor of the thyroid, that is, medullary thyroid carcinoma. A brief overview of the understanding of this tumor's identification as a lesion of C cells and its familial and syndromic associations will be presented. Then, a discussion of the various mimics of medullary carcinoma will be given with an approach to the types of tests that can be done to arrive at a correct diagnostic conclusion. This review will focus on practical "tips" for the practicing pathologist.