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Purpose: Non-invasive encapsulated follicular variant of papillary thyroid cancer was reclassified as non-invasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP). These neoplasms have an extremely low malignant potential. The aim of this study was 1) to assess the prevalence of NIFTP in patients with papillary thyroid carcinoma, 2) to evaluate their outcomes and 3) to determine their molecular profile.Methods: Multicenter, descriptive, retrospective study. Patients with papillary thyroid cancer diagnosed from January 2006 to December 2016 from 11 referral centers were included. Diagnosis of NIFTP was based on criteria described by Nikiforov et al. in 2018. At least two pathologists agreed on the diagnosis. Two thousand six hundred and seventy-seven papillary thyroid cancer patients were included; 456 (17%) of them were follicular variant papillary thyroid cancer, and 30 (1.12%) fulfilled diagnostic criteria for NIFTP.Results: Each of the 30 included patients underwent a total thyroidectomy, and 50% were treated with radioiodine (median dose 100 mCi). After a median follow up of 37 months, 84% of patients had an excellent response, 3% had an indeterminate response and data was missing in the remaining 13%. No metastatic lymph nodes, distant metastases or recurrences were found. RAS mutations were detected in 4 patients (13%).Conclusion: The prevalence of NIFTP in our series is amongst the lowest reported. Excellent outcomes of patients underscore their low malignant potential. Molecular findings differ from other series, probably related to environmental or ethnic features of our population and the meticulous criteria for diagnosing NIFTP.

We describe the clinicopathological and immunohistochemical features of three spindle (sarcomatoid) basaloid squamous carcinomas in three men aged 73, 69, and 59 years with a history of tobacco and alcohol abuse. Two tumors were located in the hypopharynx and one was located in the nasal cavity. The three tumors have a pedunculated polypoid appearance. Histologically, they were composed of conventional basaloid squamous carcinomas with extensive malignant spindle cell proliferation, comprising more than 50% of the tumor. The sarcomatoid component demonstrated immunoreactivity with one or more epithelial markers. One case in addition expressed CD99 and Bcl-2 and was originally diagnosed as monophasic synovial sarcoma; however, a subsequent biopsy disclosed basaloid squamous cell carcinoma with sarcomatoid stroma. Two patients were treated with surgery and radiation whereas one refused therapy. The patients were alive 14 (case patient 1), 10 (case patient 2), and 8 (case patient 3) months after diagnosis. In the absence of evidence from immunohistochemical or electron microscopy studies, a polypoid malignant spindle cell tumor of a mucosal surface of the upper aerodigestive tract should be considered a sarcomatoid carcinoma until proven otherwise. The type of epithelial component would determine the subtype of sarcomatoid carcinoma.

We present the cases of 2 pediatric patients with low-grade nasopharyngeal papillary adenocarcinoma with features suggestive of thyroid origin. Both cases showed strong nuclear immunoreactivity for thyroid transcription factor–1 protein and positive immunostaining for cytokeratins 7 and 19. After thyroid imaging studies, local excision was performed in both patients. The patients remain free of disease 2 and 15 years after treatment, with no evidence of lesions in the thyroid or elsewhere.

Teratocarcinosarcomas are rare malignant neoplasms histologically characterized by the presence of benign and malignant epithelial and mesenchymal elements. They are seen almost exclusively in the sinonasal tract of men. We report two cases of teratocarcinosarcomas involving the posterior pharyngeal wall in a 55-year-old male and 60-year-old men. The tumors consisted of epithelial components including squamous, neuroendocrine, and glandular structures; neuroepithelium, and mesenchymal components with prominent rhabdomyoblastic, osteoblastic and chondroid differentiation. Immunohistochemical studies demonstrated markers characteristic of each component. The tumors were resected, and the patients received postoperative radiation therapy. One patient is alive with recurrent tumor 33 months after treatment and the other died 26 months after radiation therapy with distant metastasis.