Sarcoma of the thyroid region mimicking Riedel's thyroiditis

Abstract

Because sarcomas of the anterior lower neck region occur so infrequently, they are not usually considered in the diVerential diagnosis of Riedel's thyroiditis. Riedel's thyroiditis itself may be confused on clinical grounds alone with malignant neoplasms because of its invasive features. Sarcomatoid carcinoma is the main entity to be discarded in this regard. This is accomplished through histological examination by the finding of carcinomatous areas and/or reactivity with epithelial markers. These features also set apart sarcomatoid carcinoma from true sarcomas. This report concerns a patient with a sarcoma of the anterior lower neck region which was initially suspected to be Riedel's thyroiditis or sarcomatoid carcinoma on clinical and radiological grounds. A peroperative biopsy was interpreted by two independent pathologists as consistent with Riedel's thyroiditis. The subsequent clinical course and postmortem examination demonstrated a high grade sarcoma with metastasis to both lungs and the pleura, and invasion of adjacent neck structures. Nevertheless, some areas of the postmortem material showed a microscopic pattern similar to mediastinal fibrosis, raising the possibility of the malignant transformation of a fibrosclerotic lesion. (J Clin Pathol 2001;54:570-572) Keywords: Riedel's thyroiditis; sarcomatoid carcinoma; fibrous histiocytoma; diVerential diagnosis On 1 August 1994, a 65 year old white man was referred to our hospital with hoarseness of six months duration. The patient was also found to have stridor and dyspnea related to exercise. There was no antecedent of radiotherapy or thyroid pathology and past medical history was unremarkable except for chronic bronchitis.Scintigraphic study showed no uptake of tracer in the right thyroid lobe, isthmus, and lower pole of left lobe, which was coincident with a palpable mass at the same level.A computer assisted tomography scan revealed diVuse enlargement of the thyroid gland, which was more conspicuous in the right lobe and caused displacement, compression, and stenosis of the trachea. Displacement of the carotid sheath on the right and endothoracic growth were noted. Ultrasonography showed diVuse enlargement without nodularity.A barium swallow detected stenosis and displacement of the oesophagus. Indirect laryngoscopy revealed limitation of vocal cord movements and paralysis of the right vocal cord. Laryngeal and oesophageal mucosa were normal and the skin was not involved. The only abnormal laboratory test result was an erythrocyte sedimentation rate of 65 in the first hour.At surgery, a large fibrous mass of stony hard consistency was found firmly adherent to the trachea and invading the skeletal muscles and right carotid sheath. Remnants of the thyroid gland could be identified on the left side only. Resection was not possible. Biopsies from both sides of the mass overlying the trachea were taken, and tracheal intubation was performed. Peroperative biopsy was interpreted as consistent with Riedel's thyroiditis. Microscopic examination of th...

Invasive Fibrous Thyroiditis (Riedel Thyroiditis): The Mayo Clinic Experience, 1976–2008

“…In our cases, diagnosis was not possible by FNA biopsy; tissue diagnosis and evidence of extrathyroidal extension of fibrosis was needed for diagnosis of IFT in our series. Conditions such as fibrotic Hashimoto's thyroiditis, sarcoma of the thyroid (22), and anaplastic carcinoma may mimic IFT (23,24). Diffuse sclerosing papillary thyroid cancer may have histologic similarities and should be ruled out (25).…”

Riedel’s thyroiditis: Diagnostic and therapeutic difficulties

“…The macroscopic and histopathologic appearance of the disease described in the literature is as follows: fibrous thyroid gland stiff as wood, fibrosis extending beyond the thyroid capsule to the perithyroidal neck structures, microscopically without accompanying granulomatous inflammatory component, displacement of fibrous tissue with normal parenchyma of the thyroid (6). Lymphoma, anaplastic carcinoma, sarcomas, and Hashimoto's thyroiditis should definitely be included in the differential diagnosis of Riedel's thyroiditis (7)(8)(9)(10). In the present case, the absence of atypical cells in the biopsy specimens, intense concentration of fibrosis almost as if displaced totally by normal thyroid tissue, extansion to the outward of the thyroid capsule and neck and the fibrotic process affecting the adjacent neck structures at a level of compression made us think of Riedel's thyroidits as the first choice.…”

Riedel's thyroiditis in a black African: A case report and review of literature

“…There have been reports of Riedel thyroiditis mimicking anaplastic carcinoma and sarcoma of the thyroid in the past. [18] Another strong differential diagnosis of Riedel's thyroiditis is fibrosing variant of Hashimoto's thyroiditis which is characterized by extensive fibrous proliferation but without extension into the surrounding structures, thus distinguishing this lesion from Riedel's thyroiditis. [9,19] Which is characterized by the progressive fibrous replacement of the thyroid gland, with a spread of dense, inflamed fibrous tissue outside the thyroid capsule, involving the adipose tissue, muscle, and nerves that may encase vessels, parathyroid glands, trachea, and esophagus as is noted in this case.…”