Cytopathology of mesenchymal tumors of the thyroid gland: analysis of 12 cases from multinational institutions with review of the literature

INTRODUCTION

Mesenchymal tumors of the thyroid gland are extremely rare. We report the cytomorphologic characteristics of 12 mesenchymal tumors occurring in the thyroid gland and highlight the diagnostic difficulties encountered in their cytologic evaluation.

MATERIALS AND METHODS

The cytopathology and surgical pathology archives from 5 large institutions were searched for thyroid mesenchymal tumors that had an FNA available for review. Clinicopathologic and cytomorphologic characteristics for each case were evaluated.

RESULTS

Twelve cases of mesenchymal tumors occurring in the thyroid were identified in our search. Patient age ranged from 28 to 84 years (median, 60 years). The cases occurred in 7 women and 5 men. The tumor size ranged from 1.4 to 14 cm (median, 3.3 cm). The tumors were as follows: hemangioma (n = 4; 33.3%), angiosarcoma (n = 2; 16.7%), schwannoma (n = 2; 16.7%), solitary fibrous tumor (n = 2, 16.7%), metastatic synovial sarcoma (n = 1, 8.3%) and metastatic pleomorphic rhabdomyosarcoma (n = 1, 8.3%). The cytomorphologic features of the tumors were similar to those of their counterparts occurring in different sites. An accurate diagnosis was achieved in six primary thyroid mesenchymal cases (60%). Five patients (41.7%) underwent total thyroidectomy, and 3 patients received partial thyroidectomy (25%). Three patients (25%) did not receive a thyroidectomy and subsequent surgical information was not available in 1 case (8.3%).

CONCLUSIONS

Mesenchymal tumors of the thyroid are extremely uncommon. Cytologic diagnosis of these tumors is often challenging due to the morphologic overlap with diverse epithelial and non-epithelial thyroid lesions. Ancillary studies such as immunohistochemistry and molecular studies are essential for accurate diagnosis.

Malignant Ossifying Fibromyxoid Tumor of the Chest Wall Metastasized to the Lung Even After Complete Resectioning of the Primary Tumor - A Case Report and a Comprehensive Review

An ossifying fibromyxoid tumor is a soft tissue neoplasm with ambiguous differentiation and low metastatic potential. Most cases involve the lower extremities, followed by the trunk, the upper extremities, and the head and neck region. It mainly arises in 40-70 years of age, and men dominate the disease's gender distribution. In the described types of ossifying fibromyxoid tumors, there are three variants: one is benign (typical), the second is malignant, which carries the risk of disease recurrence or metastases, and the third is atypical, which does not meet the criteria of either typical or malignant. Here, we present an interesting case of a malignant ossifying fibromyxoid tumor of the chest wall that metastasized to the lungs even after complete resection of the primary tumor. A 64-year-old man had a 4.0 cm malignant ossifying fibromyxoid tumor in his chest wall two years ago, and at that time, the tumor was removed entirely. On pathology review, it was noted to have 20 mitotic figures per 50 high-power fields, but no actual grade was given. He was given postoperative radiation. His recent computed tomography (CT) chest with contrast showed a new right upper lung lobe nodule measuring 0.78 cm compared to the previous contrast-enhanced CT chest six months ago. It was worrisome for metastasis. F-18 FDG positron emission tomography scan revealed sub-centimetric pulmonary nodules in the right upper lobe. Right upper lobe lung biopsy showed spindle cell neoplasm morphologically consistent with the patient's known history of malignant ossifying fibromyxoid tumor. Biopsy demonstrated fragments of the bronchial wall and alveolated lung parenchyma with a focal spindle cell proliferation demonstrating a fibromyxoid matrix. The patient was referred to the oncologist for further management. In conclusion, aggressive malignant ossifying fibromyxoid tumors can be found in atypical locations, e.g., the chest wall. Therefore, early diagnosis is crucial because of the high chances of metastasis to distant organs (including the lung) even after complete resection of the primary tumor. Even in asymptomatic patients, it is necessary to complete long-term follow-up for recurrence and metastasis surveillance of ossifying fibromyxoid tumors. Early recognition of recurrence or metastasis can decrease morbidity and mortality and improve overall organ function and patient survival.

Prevalencia de tumores metastásicos en la glándula tiroides. Revisión sistemática y metanálisis

Introducción y objetivo: Los tumores metastásicos en la glándula tiroides complican el diagnóstico, el tratamiento y el pronóstico del paciente. El objetivo es conocer la prevalencia de las metástasis en la glándula tiroides referida en la literatura médica y los tumores primarios que con más frecuencia metastatizan en la glándula tiroides. Método: Se realizó una revisión bibliográfica sistemática en las bases de datos de PubMed, La Biblioteca Cochrane y Scopus. Los artículos seleccionados se dividieron en dos grupos, series clínicas de pacientes en los que se hallaron metástasis en tiroides (grupo A) y series de hallazgos de metástasis en tiroides en autopsias (grupo B). Se realizó metanálisis de prevalencia para cada grupo de artículos siguiendo el modelo de efectos aleatorios. Resultados: La prevalencia en cada grupo con su índice de confianza al 95% fue 0.00479 (0.002-0.007) para el grupo A y 0.0362 (0.014-0.059) para el grupo B. La prevalencia de metástasis halladas en autopsias fue 7,58 veces mayor que en los estudios clínicos. En el grupo A la edad media fue 60.82 y en el grupo B 57.20. En ambos grupos las metástasis halladas en tiroides fueron más frecuentes en el sexo femenino. La localización del tumor primario fue diferente en ambos grupos, en el grupo A fue el cáncer de riñón y en el grupo B el cáncer de mama. La variabilidad de la prevalencia de metástasis en tiroides en los diferentes artículos de ambos grupos hace que este estudio tuviese una alta heterogeneidad (índice I2 y Q). Los funnel plot de ambos grupos indicaron alto sesgo de publicación. Discusión: La diferente prevalencia entre series clínicas y autopsias puede implicar que la detección de metástasis en tiroides en la clínica está infradiagnosticada. La razón de esto podría ser que las metástasis intratiroideas se presentan de forma asintomática siendo diagnosticadas como hallazgo casual en autopsias. En otras ocasiones se presentan como un nódulo tiroideo años después del tumor primario, lo que condiciona el diagnóstico. Conclusiones: La prevalencia de metástasis en tiroides es superior en las series de autopsias que en series clínicas (hasta 6.67 veces más frecuente en nuestro estudio). Las metástasis intratiroideas probablemente están infradiagnosticadas por cursar sin clínica siendo diagnosticadas como hallazgo casual en autopsias. Los tumores primarios más frecuentes fueron el riñón (series clínicas) y la mama (series de autopsias).

Ossifying fibromyxoid tumor: morphology, genetics, and differential diagnosis

Ossifying fibromyxoid tumor (OFMT) is a soft tissue neoplasm of uncertain differentiation and intermediate (rarely metastasizing) biologic potential, with typical morphologic features, of an encapsulated, lobulated tumor comprising uniform polygonal cells within fibromyxoid stroma, which is surrounded by or contains metaplastic bone, classically as a peripheral rim of lamellar bone. Ossifying fibromyxoid tumor can arise at almost any site, although most frequently occurs within the extremities and trunk. Although most behave in a benign fashion, tumors can rarely show atypical or malignant features. It is now established that OFMTs represent translocation-associated tumors, with up to 85% associated with recurrent gene rearrangements, mostly involving the PHF1 gene (including in typical, atypical, and malignant neoplasms), with EP400-PHF1 in approximately 40% of tumors, and ZC3H7B-BCOR, MEAF6-PHF1, and EPC1-PHF1 fusions also described. Correct diagnosis is clinically important to ensure correct treatment and prognostication, both to avoid overdiagnosing OFMT as a malignant neoplasm such as osteosarcoma and also because of the propensity for aggressive behavior in a small number of OFMT. We review OFMT, with emphasis on the morphologic spectrum, recent molecular genetic findings, and the differential diagnosis.