Primary Squamous Cell Carcinoma of the Thyroid: A Case Report and Literature Review About a Rare Entity

A Competing Risk Nomogram for Prediction of Prognosis in Patients With Primary Squamous Cell Thyroid Carcinoma

Objective: Primary squamous cell thyroid carcinoma (PSCTC) is an extremely rare carcinoma, accounting for less than 1% of all thyroid carcinomas. However, the factors contributing to PSCTC outcomes remain unclear. This study aimed to identify the prognostic factors and develop a prognostic predictive model for patients with PSCTC. Methods: The analysis included patients diagnosed with thyroid carcinoma between 1975 and 2016 from the Surveillance, Epidemiology, and End Results database. Prognostic differences among the 5 pathological types of thyroid carcinomas were analyzed. To determine prognostic factors in PSCTC patients, the Cox regression model and Fine-Gray competing risk model were utilized. Based on the Fine-Gray competing risk model, a nomogram was established for predicting the prognosis of patients with PSCTC. Results: A total of 198,757 thyroid carcinoma patients, including 218 PSCTC patients, were identified. We found that PSCTC and anaplastic thyroid cancer had the worst prognosis among the 5 pathological types of thyroid carcinoma (P < .001). According to univariate and multivariate Cox regression analyses, age (71-95 years) was an independent risk factor for poorer overall survival and disease-specific survival in PSCTC patients. Using Fine-Gray regression analysis, the total number of in situ/malignant tumors for patient (Number 1) (≥2) was identified as an independent protective factor for prognosis of PSCTC. The area under the curve, the concordance index (C-index), calibration curves and decision curve analysis revealed that the nomogram was capable of predicting the prognosis of PSCTC patients accurately. Conclusion: The competing risk nomogram is highly accurate in predicting prognosis for patients with PSCTC, which may help clinicians to optimize individualized treatment decisions.

Paraneoplastic Manifestation of Primary Squamous Cell Cancer of the Thyroid Gland

Paraneoplastic manifestation (PNM) of cancers is a non-metastatic, non-invasive systemic effect of malignancies due to chemokines and hormones produced by the primary neoplasm. Squamous cell cancers (SCCs) are known to present with PNM. Primary SCC of thyroid accounts for <1% of all thyroid malignancies and carries a very poor prognosis. We present a rare case of SCC arising from the thyroid gland who presented with fever, leukemoid reaction and hypercalcemia as part of PNM. A 67-year-old male patient presented with two months history of intermittent high-grade fever, weakness, loss of weight and appetite. Examination revealed a large (~10 cm) hard swelling over the right side of the neck. Investigations revealed neutrophilic leukocytosis, elevated C-reactive protein (CRP) and procalcitonin and hypercalcemia with a normal thyroid-stimulating hormone (TSH). The fever workup was negative for infection. Fine-needle aspiration cytology (FNAC) and core biopsy of the thyroid mass revealed malignant cells with squamous differentiation. An extensive search for possible other primary was ruled out by triple endoscopy. The combination of fever, neutrophilic leukocytosis, hypercalcemia and squamous malignancy was consistent with a diagnosis of PNM of SCC. A fluorodeoxyglucose-positron emission tomography (FDG-PET) CT scan showed a heterogeneously enhancing mass lesion in the right lobe of the thyroid with some retrosternal extension. He underwent total thyroidectomy with bilateral central compartment neck dissection. Final histopathology revealed moderately differentiated SCC of the thyroid. Concurrent chemoradiation was given. Despite continued chemotherapy, he succumbed to illness within six months of diagnosis. Primary SCC of thyroid (PSCCT) is a rare malignancy. It is a highly aggressive tumor having a poor prognosis with a median survival time of about 9-12 months and less clearly defined therapy due to its rarity. Paraneoplastic manifestation of PSCCT is known. As fever, leukemoid reaction and hypercalcemia can be a paraneoplastic manifestation, one should think of PSCCT.

Collision tumors of the thyroid. A special clinical and pathological entity

Thyroid collision tumors are rare entities that designate two histologically and morphologically distinct tumors that occur simultaneously or as metastases from other organs within the thyroid. Medullary and papillary carcinoma co-occurrence is the most frequent. Several theories tried to explain the pathogenic mechanisms underlining collision tumors, including the theory which assumes that one tumor predisposes the other, stem cell theory, and random effect theory, but their combination better explains the origin of these tumors. Hypotheses about common genetic behavior responsible for the pathogenesis have also been suggested, such as the involvement of germline mutation of RET (Rearranged during Transfection) proto-oncogene in medullary thyroid carcinoma and papillary thyroid carcinoma coexistence, but there is controversy on this topic. Management of thyroid collision tumors is challenging owing to the presence of two distinct tumors with different biological aggressiveness, treatments options, and prognosis, and needs to be individualized.