Ectopic Poorly Differentiated (Insular) Carcinoma of the Thyroid:Report of a Case Presenting as an Anterior Mediastinal Mass

Abstract

A case is presented of an anterior mediastinal mass arising in a 64-year-old woman that showed on histologic, immunopathologic, and ultra-structural examination features of a poorly differentiated (insular) thyroid carcinoma. The tumor in this patient most likely arose from ectopically displaced thyroid tissue on the basis of a developmental defect. The clinicopathologic features and differential diagnosis of the lesion in the setting of its mediastinal location are discussed. Ectopic poorly differentiated (insular) carcinoma of the thyroid should be added to the list of mediastinal tumors showing a solid or insular growth pattern.

Personalized Management of Malignant and Non-Malignant Ectopic Mediastinal Thyroid: A Proposed 10-Item Algorithm Approach

“…In additional to these clinical elements that are directly connected to the presence of the mediastinal lesion, highly aggressive malignancy in EMTs might be detected due to local or distant malignant spreading as the first step of further undergoing EMT identification. Here, we introduce the cases with thyroid cancer in EMTs (regardless of the scenario of detection) according to our methods [36,37,41,42,55,[58][59][60][61][62][63][64][65][66][67][68][69][70][71][72] (Table 2).…”

“…Table 2. Case reports of EMT underlying different types of malignancy according to our methods; the display starts with the most recent publication date [36,37,41,42,55,[58][59][60][61][62][63][64][65][66][67][68][69][70][71][72]. Regardless of the pathological traits, awareness of EMTs is essential, while removal was decided in most of the cases (rather than conservative approach) depending on the location and EMT anatomical features; the risk of malignancy (the rate of conversion from benign to a malignant EMT is not clearly understood, especially in long standing goiter-like EMT); the ectopic tissue enlargement with compressive symptoms/signs such as respiratory obstruction or compression on mediastinal organs; the risk of hemorrhage [84]; the patient's co-morbidities and medical/surgical history as well as the general health status [7,13].…”

“…One short note: 19 papers introduced a single case report per article [36,37,41,42,[58][59][60][61][62][63][64][65][66][67][68][69][70][71][72] and another publication presented two patients [55], leading to a total of 21 patients with any type of malignancy in EMTs. Specifically, primary thyroid cancer was identified in 20 patients (plus, a case of a one newborn displayed an immature teratoma hosted by the EMT [68]).…”

Insular Type of Papillary Thyroid Carcinoma- A Case Report and Literature Review

“…As the tumor growth pattern in insular thyroid cancer is infiltrative, as proven by the case, it may be identical to that of neuroendocrine neoplasms including carcinoid or medullary thyroid cancer. Differentiation between these tumors can be identified by the presence of eosinophilic colloid-like material and thyroglobulin within the follicules of insular thyroid cancer, in addition to the absence of calcitonin, carcinoembryonic antigen and other neuroendocrine markers stain [6].…”

Ectopic Thyroid Tissue in the Mediastinum Characterized by Histology and Functional Imaging with I-123 SPECT/CT

“…There are circumstances in which thyroid tissue may be found outside the gland due to faulty embryogenesis related to genetic factors, mechanical implantation secondary to surgical intervention or trauma, a sequestered thyroid nodule adjacent to the gland but without anatomic connection, or thyroid tissue as a component of a teratoma [ 1 – 4 ]. The lingual area is the most common location of ectopic thyroid tissue [ 3 , 5 , 6 ], and ectopic thyroid tissue is occasionally localized within mediastinum [ 7 – 13 ]. Most of patients with ectopic thyroid presented with symptoms of hypothyroidism, and rare cases of hyperthyroidism with histological features similar to Graves' disease have been reported [ 14 – 18 ].…”