Massive squamous metaplasia of the thyroid gland – Report of three cases

Solid Cell Nests in Hashimoto’s Thyroiditis Sharing Features with Papillary Thyroid Microcarcinoma

“…Weak, but unequivocal, positivity of TTF-1 was also reported in one case of SCN by Ryska [25]. In our immunohistochemical analysis of TTF-1, the same antibody at the same dilution (1/50) and a similar automated immunostainer machine were used as in the Ryska study [25]. Reis-Filho [20] reported SCN to express TTF-1.…”

“…A consistent and reproducible strong reactivity for p63 (97.6%) in SCN has been reported [5,16,17,20,25,26]. p63 is consistently expressed in basal/stem cells of several types of epithelia and it is usually absent in partially or terminally differentiated cells [29][30][31][32].…”

Expression of Cytokeratin 19 and Protein p63 in Fine Needle Aspiration Biopsy of Papillary Thyroid Carcinoma

“…35 It is strongly expressed in the basal and parabasal layers, the stem cell reservoir of squamous epithelia and tumors of squamous origin. 36,37 p63 Has been recently found in many different benign lesions of the thyroid, such as Hashimoto's thyroiditis, 18,38 massive squamous metaplasia 39 and solid cell nests 19 and in malignant tumors, such as sclerosing mucoepidermoid carcinoma with eosinophilia, 40 thyroid carcinoma showing thymuslike differentiation 41 and primary thyroid papillary carcinomas of branchial cleft cysts 42 and in papillary carcinoma 20,22,43 and anaplastic carcinoma. 24,44 In our cases, p63 positivity was observed in 74% of cytologic smears and in 93% of PTC histologic specimens, while only 1 benign case (4.5%) showed a few p63-positive cells in FNAB smears, but coexpression of CK19 was not present.…”

BRAF mutation in solid cell nest hyperplasia associated with papillary thyroid carcinoma. A precursor lesion?

“…Although squamous metaplasia is usually associated with inflammatory processes [13], in our case, no alteration in follicular cells surrounding the SCNs or dyskeratosis was identified. Massive squamous metaplasia without C cells has been reported in 5 cases of Hashimoto thyroiditis [14]. Squamous metaplasia has been called ductal metaplasia by Caillou [15] and interpreted as a phylogenic regression to an exocrine structure, secondary to chronic injury.…”