| Abstract|| |
Papillary thyroid carcinoma (PTC) is a common malignancy with multiple variants, some of which are rarely encountered in routine surgical pathology practice. PTC with exuberant nodular fasciitis-like stroma or PTC with fibromatosis-like stroma is one such variant. This tumor is characterized by an abundant stromal component with an intervening epithelial component with the typical morphologic features of PTC. We describe gross and histopathological features of this rare variant of papillary carcinoma in a 38-year-old female and review the literature. We also discuss the importance of a thorough search for epithelial components within any fibroproliferative lesion of the thyroid and address the diagnostic difficulties created by the tumor's extensive stromal component. Given the rarity of this condition, the experience gained from the present case is a useful addition to the current knowledge on disease prognostication and management.
Keywords: Nodular fasciitis-like stroma, papillary carcinoma, thyroid
|How to cite this article:|
Mardi K. Papillary thyroid carcinoma with nodular fasciitis-like stroma: A rare variant with distinctive morphology. Indian J Pathol Microbiol 2017;60:390-2
|How to cite this URL:|
Mardi K. Papillary thyroid carcinoma with nodular fasciitis-like stroma: A rare variant with distinctive morphology. Indian J Pathol Microbiol [serial online] 2017 [cited 2021 Jul 23];60:390-2. Available from: https://www.ijpmonline.org/text.asp?2017/60/3/390/215399
| Introduction|| |
Papillary thyroid carcinoma (PTC) with nodular fasciitis-like stroma (PTC-NFS) is a rare variant of PTC.,,,, The term “PTC with fibromatosis-like stroma (PTC-FMS)” has been used as a synonym to describe this variant. It is characterized by extensive proliferation of fibroblasts and myofibroblasts in the tumor stroma. The first case was described in 1989, since then, nearly 25 cases have been reported so far. We herein describe an additional case of PTC-NFS which developed in a 38-year-old female.
| Case Report|| |
A 38-year-old female presented with a lump in the left side of her neck, which had gradually increased in size during the previous 2 months. Physical examination revealed a firm mass measuring 3 cm × 3 cm in size located in the left lobe of the thyroid gland moving with deglutition. Her past medical history was unremarkable. Thyroid function tests were within normal range. Ultrasonography revealed enlarged left lobe of the thyroid with heterogeneous echotexture. Radiological diagnosis of multinodular goiter was suggested. The fine-needle aspiration of enlarged left lobe did not yield material initially. Repeat aspiration revealed scanty cellular material showing follicles with nuclear features of papillary carcinoma. The possibility of follicular variant of papillary carcinoma was suggested. Total thyroidectomy was done. On gross examination, the left lobe of the thyroid was enlarged and was measuring 7 cm × 5 cm × 3 cm, and serial sectioning revealed a growth replacing the thyroid parenchyma of the entire left lobe. Cut surface of growth revealed gray-white trabeculated appearance with focal yellow areas [Figure 1]a. Histologically, the tumor consisted of two distinct components: stromal and epithelial. There was a predominance of stromal component (approximately 80% of tumor) with scant epithelial component [Figure 1]b. The stromal component consisted of spindle-shaped cells arranged in interlacing fascicles in an abundant fibromyxoid matrix. The stromal cells had neither nuclear atypia nor mitotic figures. Occasional lymphocytic infiltration or extravasated red blood cells were also identified. Epithelial components comprised of clusters of variably sized thyroid follicles lined by cuboidal epithelium that showed optically clear “orphan annie” nuclei with frequent nuclear grooves and intranuclear inclusions [Figure 2]a. Immunohistochemically, the spindle cells exhibited diffuse cytoplasmic stain with vimentin and smooth muscle actin [Figure 2]b. In contrast, they showed negative staining with cytokeratin and thyroglobulin. A diagnosis of follicular variant of papillary carcinoma with NFS was rendered.
|Figure 1: (a) Cut surface of the left lobe of thyroid shows fibrotic growth replacing the thyroid parenchyma. (b) Photomicrograph revealing exuberant stromal component and scanty epithelial component of the tumor (H and E, ×10)|
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|Figure 2: (a) Higher magnification revealing spindle cells in loose myxoid matrix with a foci follicular variant of papillary carcinoma (H and E, ×40). (b) Stromal cells showing positivity for vimentin (IHC, ×40)|
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| Discussion|| |
PTC is known to have several morphologic variants. PTC can occasionally manifest with extensive proliferation of the stroma, resembling fibroblastic/myofibroblastic proliferative lesion in the soft tissue. This rare variant of PTC has been described with the terms “PTC-NFS” or “PTC-FMS.” Histologically, it consists of stromal components rich in spindle cells, occupying 60%–80% of tumors, and small foci of epithelial components showing typical features of conventional PTC. Ultrastructural and immunohistochemical findings have revealed that the spindle cells in the tumor stroma have characteristics of myofibroblasts.
Basu et al. have done systematic review of the existing literature on PTC-NFS, aiming to explore the patient characteristics and clinical behavioral pattern of this rare entity and to make appropriate recommendations on management strategy. They concluded that the age of presentation ranges from 20 to 82 years, with a mean of 44.5 years. Female preponderance was observed, with a female to male ratio of 3:1. No racial predilection was observed. Tumor size varied from 2 to 9 cm along its greatest diameter (mean = 4.3 cm). Metastasis to lymph nodes at presentation occurred in 25% of cases. Metastasis to surrounding structures (e.g., parathyroid and skeletal muscle) was observed in 12.5%.
The pathogenesis of the spindle cell proliferation in this variant of thyroid papillary carcinoma (TPC) is still unknown and rather confusing. Chan et al. have interpreted the stromal proliferation as a reaction to the carcinoma cells. In our case, the stromal component was confined to the tumor. The spindle cells had neither atypia nor mitosis. These findings support that the stromal proliferation may be reactive in nature. Toti et al. have found that numerous carcinoma cells in the stromal area were immunoreactive for transforming growth factor beta (TGF-β), suggesting that TGF-β may be responsible for the stromal change of the tumors. However, Naganuma et al. failed to find immunoreactivity for TGF-β in both stromal cells and carcinoma cells. Further studies are necessary to uncover the pathogenesis of the marked spindle cell proliferation in these tumors.
To characterize the stromal components, Na et al. investigated the expression of several immunohistochemical markers which have been shown to be expressed differently in nodular fasciitis (NF) and fibromatosis (FM). The immunostaining results demonstrated nuclear and cytoplasmic accumulation of β-catenin, cytoplasmic TGF-β expression, and nuclear Smad expression in the stromal cells, suggesting that the stromal cells have similar molecular profiles to those of FM rather than NF.
The stromal proliferation makes aspiration of the neoplastic cells of papillary carcinoma difficult and results in diagnostic error, as does the intraoperative frozen section. It has been previously shown that fine-needle aspiration in this disease can only contain spindle cells.
The importance of recognizing this variant of PTC is that, when a fibroproliferative lesion is detected in the thyroid gland, a careful search should be made for PTC. Fine-needle aspiration cytology usually aspirates the spindle cells of the fibrous stroma, and the PTC component is missed. Extensive sampling of the tumor should be done, and diligent search should be made for focal PTC. Furthermore, recognition of this variant is particularly important in the differential diagnosis from extensive fibrosis observed in other malignancies of the thyroid glands showing aggressive clinical course, such as diffuse sclerosing variant of PTC and carcinosarcoma. The stroma in the diffuse sclerosing variant of PTC is rich in lymphocytic infiltrate and psammoma bodies, but fibroblastic proliferation is rarely seen. Carcinosarcoma can be differentiated by the detection of obvious malignant features of spindle cells in the tumor stroma. It is especially important to differentiate between TPC-NFS and TPC with anaplastic transformation (spindle cell anaplastic carcinoma) because anaplastic carcinoma of the spindle cell type is a fatal disease.
The differential diagnosis of TPC-NFS also includes a large variety of thyroidal spindle cell proliferations. TPC with an exuberant NFS can be distinguished from the extensive fibrosis observed in some forms of thyroiditis, such as the fibrous variant of Hashimoto's thyroiditis and Riedel's thyroiditis, by the presence of papillary carcinoma. Conventional TPC is frequently accompanied by a fibrous stroma and scars that are formed as a host reaction; however, it seldom forms nodular tumors. Benign mesenchymal tumors, including solitary fibrous tumor, may arise in the thyroid gland. However, the demonstration of TPC after conducting a thorough sampling may lead to the correct diagnosis.
Although the patterns of disease progression and the clinical outcome are still not clarified because of the rarity of this variant, it may be more aggressive than classic PTC. There have been no reports of pulmonary or skeletal metastasis at presentation. Most cases are being managed by the similar surgical strategy for the classic PTC.
| Conclusion|| |
PTC-NFS is a rare variant of papillary carcinoma with distinctive morphology and should be distinguished from other more aggressive malignancies of the thyroid with fibrosis as well as from a variety of spindle cell proliferations in the thyroid. Pathologists should make a careful search for PTC whenever they encounter a fibroproliferative lesion in the thyroid.
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