Papillary thyroid carcinoma with nodular fasciitis-like stroma - an unusual variant with distinctive histopathology: A case report

Abstract

Background: Papillary thyroid carcinoma (PTC) is regarded as a fairly common endocrine malignancy, which can be divided into different multiple variants due to wide morphologic differences. The majority of PTC variants have been reported, but PTC with nodular fasciitis-like stroma (NFS) is a rare pathological variant and has been infrequently reported in the relevant literature. This condition involves abundant reactive stromal components rich in spindle cells, which may account for 60%-80% of the tumor along with a typical papillary carcinoma.

Case summary: A 44-year-old man presented with a 4-mo history of a palpable mass over the anterior aspect of the left neck, the tumor demonstrated gradual enlargement but was painless during the 4 mo prior to discovery. Thyroid function test results were normal. Physical examination showed an enormous and firm nodular mass in the left lobe of the thyroid gland extending to the level of the hyoid bone. Ultrasonography of the neck revealed a well-defined heterogeneous lesion measuring around 5.0 cm × 4.0 cm with a hypoechoic complex nodule, decreased vascularity and speckles of microcalcification. The patient underwent left thyroidectomy with central compartment lymph node dissection. Final histopathological examination confirmed the diagnosis of PTC with extensive fibromatosis-like stroma combined with typical PTC. The patient was asymptomatic at the 3-mo follow-up.

Conclusion: PTC-NFS is a rare pathological variant and its diagnosis and prognosis may be similar to typical papillary carcinoma.

Keywords: Case report; Differential diagnosis; Metaplasia; Neck ultrasound; Nodular fasciitis-like stroma; Papillary thyroid carcinoma; Spindle cell.

Figure 1

Neck ultrasonography. A and B: Ultrasonography image of the neck showed a mixed echoic and horizontal nodule measuring approximately 5.1 cm × 3.1 cm × 2.9 cm in the left thyroid gland; C and D: Fine needle aspiration revealed a mass of hyperplastic glandular epithelial cells and infiltration of short spindle cells.

Figure 2

Histopathological features of papillary thyroid carcinoma with nodular fasciitis-like stroma. A: The papillary tumor consisted of extensive stromal proliferation and classical papillary thyroid carcinoma cells; B: The stromal part of spindle cells showed vigorous proliferation of myoblasts, lymphocytes infiltration and exudated red blood cells; C: Lymphocytic infiltration was also seen around the tumor stroma.

Figure 3

Immunohistochemical features of papillary thyroid carcinoma with nodular fasciitis-like stroma. A: The epithelial component showed significant positive expression of thyroid transcription factor-1, and Galectin-3; B: The stromal spindle cells in the tumor demonstrated prominent cytoplasmic staining with smooth muscle actin and CD34; C: Significant β-catenin staining was also found in nuclear and cytoplasmic regions. The Ki-67 proliferation index was < 3% both in the epithelial and stromal components.