Solitary fibrous tumour of the thyroid

Solitary fibrous tumour is most commonly seen in the pleura. Thyroid is one of the sites of extra-pleural SFT. A total of 13 cases of solitary fibrous tumour in the thyroid have been reported^1,3,4,7. It has also been reported in perithyroid soft tissue⁸.

Clinical features

The mean age of presentation is 48 years (range 28 to 64). There is a female predominance¹.

Macroscopic appearances

These are firm well-demarcated tumours. They may show small cystic spaces. They lack necrosis or calcification¹.

Histopathology

The proliferation of spindle cells may be sclerotic, storiform, wavy, desmoid-like, palisading or haemangiopericytic. The nuclei are bland with fine chromatin and inconspicuous nucleoli. Entrapped thyroid follicles are seen throughout these tumours.

Immunohistochemistry

CD34	positive1,5
CD99	positive1
bcl-2	positive1
vimentin	positive1
a-actin	1/7, focal1
Cam5.2	negative1
AE1/AE3	negative1
thyroglobulin	negative1
TTF-1	negative1
S-100	negative1, except any lipomatous component13
EMA	negative1
desmin	negative1

Ultrastructure

The spindle cells appear to be fibroblasts, with occasional thin filaments and a paucity of organelles. Cytoplasmic lipid droplets, pinocytotic vesicles and abundant intermediate filaments have been described.

Differential diagnosis

• fibrous variant of Hashimoto's thyroiditis⁶.

• Riedel's thyroiditis shows poorly demarcated diffuse scarring fibrosis with chronic inflammation and phlebitis.

• smooth muscle tumours

• nerve sheath tumours; may be positive for CD34.

• haemangiopericytomas show branching staghorn vessels, perivascular hyalinisation, are less fibrous and more cellular. Lipomatous haemangiopericytoma may represent a fat-containing solitary fibrous tumour¹³.

• sarcomas are rare and usually of high grade.

• spindle cell follicular adenomas are positive for cytokeratins and TTF-1.

• papillary carcinoma with an exuberant nodular-fasciitis-like stroma. the stromal cells are positive for vimentin, smooth muscle actin and desmin but negative for CD34, cytokeratin, EMA, S-100 and thyroglobulin^2,11.

• paucicellular variant of spindle cell anaplastic carcinoma shows obviously malignant foci at its periphery and is positive for epithelial markers and p53 but negative for CD34 but positive ^9,10.

• spindle epithelial tumour with thymus-like differentiation (SETTLE) occurs in children and young adults. It shows highly cellular but monotonous foci as well as bands of sclerosis and cystic glands lined by mucinous or respiratory epithelium¹².

Prognosis

No local recurrences or distant metastases have been reported.

References

¹Rodriguez, I., Ayala, E., Caballero, C., De Miguel, C., Matias-Guiu, X., Cubilla, A. L., Rosai, J. Solitary fibrous tumor of the thyroid gland: report of seven cases. Am J Surg Pathol 2001;25:1424-8.

²Terayama, K., Toda, S., Yonemitsu, N., Koike, N., Sugihara, H. Papillary carcinoma of the thyroid with exuberant nodular fasciitis- like stroma. Virchows Arch 1997;431:291-5.

³Kie, J. H., Kim, J. Y., Park, Y. N., Lee, M. K., Yang, W. I., Park, J. S. Solitary fibrous tumour of the thyroid. Histopathology 1997;30:365-8.

⁴Cameselle-Teijeiro, J., Varela-Duran, J., Fonseca, E., Villanueva, J. P., Sobrinho-Simoes, M. Solitary fibrous tumor of the thyroid. Am J Clin Pathol 1994;101:535-8.

⁵Cameselle-Teijeiro, J., Varela-Duran, J. CD34 and thyroid fibrous tumor [letter]. Am J Surg Pathol 1995;19:1096.

⁶Katz, S. M., Vickery, A. L., Jr. The fibrous variant of Hashimoto's thyroiditis. Hum Pathol 1974;5:161-70.

⁷Taccagni, G., Sambade, C., Nesland, J., Terreni, M. R., Sobrinho-Simoes, M. Solitary fibrous tumour of the thyroid: clinicopathological, immunohistochemical and ultrastructural study of three cases. Virchows Arch A Pathol Anat Histopathol 1993;422:491-7.

⁸Villaschi, S., Macciomei, M. C. Solitary fibrous tumor of the perithyroid soft tissue. Report of a case simulating a thyroid nodule. Ann Ital Chir 1996;67:89-91.

⁹Wan, S. K., Chan, J. K., Tang, S. K. Paucicellular variant of anaplastic thyroid carcinoma. A mimic of Reidel's thyroiditis. Am J Clin Pathol 1996;105:388-93.

¹⁰Canos, J. C., Serrano, A., Matias-Guiu, X. Paucicellular variant of anaplastic thyroid carcinoma: report of two cases. Endocr Pathol 2001;12:157-61.

¹¹Chan, J. K., Carcangiu, M. L., Rosai, J. Papillary carcinoma of thyroid with exuberant nodular fasciitis-like stroma. Report of three cases. Am J Clin Pathol 1991;95:309-14.

¹²Chan, J. K., Rosai, J. Tumors of the neck showing thymic or related branchial pouch differentiation: a unifying concept. Hum Pathol 1991;22:349-67.

¹³Cameselle-Teijeiro, J., J. Manuel Lopes, et al. (2003). "Lipomatous haemangiopericytoma (adipocytic variant of solitary fibrous tumour) of the thyroid." Histopathology 43(4): 406-8.

This page last revised 30.10.2003.

©SMUHT/PW Bishop