Inflammatory Pseudotumor of the Thyroid Gland Showing Prominent Fibrohistiocytic Proliferation. A Case Report

Abstract

Inflammatory pseudotumor of the thyroid gland (IPT) appears to be exceedingly rare. Histologically, 14 previously reported cases demonstrated plasma cell granuloma variant. We report here an IPT showing a predominantly fibrohistiocytic proliferation that occurred in a 75-year-old Japanese woman. Histologically, the lesion was characterized by haphazardly arranged spindle cells, histiocytes having foamy cytoplasm containing intracytoplasmic brown pigments, and small lymphocytes. Immunohistochemical study demonstrated that the spindle cells were vimentin+, desmin-, muscle-specific actin+, cytokeratin-, endomysial antibody-, anaplastic lymphoma kinase-, CD34-- CD68+/-, CD99-, cyclin D1-, bcl-2-, and antifollicular dendritic cell antibody-. IPT showing a predominant fibrohistiocytic proliferation should be differentiated from various nonneoplastic or neoplastic disorders showing spindle cell proliferation and/or exuberant fibrosis. They include Riedel's thyroiditis, fibrous variant of chronic thyroiditis, papillary carcinoma with exuberant nodular fasciitis-like stroma, paucicellular variant of anaplastic thyroid carcinoma, and solitary fibrous tumor.

Plasma Cell Granuloma of the Thyroid Gland

“…[6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23] Including the present case, 19 thyroid PCG have been recorded in the English literature. 11,[24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39] Their salient clinical findings are summarized in Table 2. Most of these PCG have occurred in asymptomatic middle-aged women or have displayed nonspecific constitutional symptoms when associated with tracheal or esophageal compression.…”

Inflammatory Myofibroblastic Tumor of the Thyroid Gland: A Brief Case Report

“…2 In comparison with IMT in other sites, most reported thyroid cases showed a prominent plasma cell infiltrate embedded in a variable degree of fibrous stroma. Only two of the reported cases exhibited morphologic features of IMT and one of those cases was reported as IMT of the thyroid gland 3,4. Extrapulmonary IMT affects children and young adults within the first two decades of life, and is rare after 30 years 1.…”

“…The mechanism, however, remains unclear in cases of IMT. Kojima et al4 reported one case of IPT with predominant fibrohistiocytic proliferation and no history or pathological findings of Hashimoto's thyroiditis.…”

Inflammatory myofibroblastic tumor of the lumbar spinal canal

“…[3] An IMT can arise in multiple anatomic locations, with the most common sites being the lungs and omentum. [4] IMTs have also been found in the head and neck region, [5] gastrointestinal tract, [6] spleen, [7] liver, [8] genitourinary tract, [9] thyroid, [10] and larynx. [11] Herein, we report a case of a 56-year-old male patient with an IMT in the lumbar spinal canal, and to the best of our knowledge, this is the first case of an IMT in that location to be reported.…”