PMC6734537_01
(A) Neck ultrasound revealing a 3.2 x 2.7 x 1.9 cm heterogenous nodule in the left thyroid lobe. (B) Neck MRI performed before left hemithyroidectomy showing no evidence of invasion of the left thyroid tumor into surrounding tissues. (C) Neck CT performed 3 months after completion thyroidectomy revealing a 2 cm fluid accumulation in the left thyroid bed (arrow) but no evidence of tumor recurrence. (D) Neck MRI revealing a 10.5 cm tumor in the left thyroid bed 16 months after the initial left hemithyroidectomy.
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Ultrasound showed a 3.2 x 1.9 x 2.7 cm heterogeneous nodule in the left thyroid lobe without calcifications or increased vascularity (Fig. 1A). Because of the worrisome physical examination, preoperative neck MRI was performed, confirming left-sided thyroid nodule but no obliterated tissue planes or invasion into adjacent structures (Fig. 1B). Because of this, a neck CT was performed 3 months after completion thyroidectomy, revealing a 2 cm fluid accumulation in the left surgical bed as well as obscuration of adjacent fat planes, consistent with postoperative changes (Fig. 1C). He returned 16 months after the initial operation with a palpable mass in his left neck and an MRI revealing a 10.5 cm tumor in the left thyroid bed (Fig. 1D).
Macroscopic and microscopic findings from left thyroid lobectomy. (A) Cut sections of thyroid demonstrating a whorled fibrotic nodule. The arrowhead shows thyroid parenchyma uninvolved by tumor. (B) Low-magnification (40x) image of interface between the tumor and adjacent thyroid parenchyma (lower right corner of panel). (C) Stromal component comprising over 90% of the tumor (100x magnification). (D) Extrathyroidal portion of tumor (lower right corner of panel) infiltrating skeletal muscle (arrow). Atrophic skeletal muscle fibers are present (arrowhead) (100x magnification). (E) Epithelial component (PTC) of the tumor and its relationship to the stromal component (100x magnification). (F) High-magnification (400x) of the PTC component of the tumor. Note the nuclear enlargement, nuclear irregularity, and chromatin pallor. Panels B-F stained with hematoxylin & eosin.
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On gross examination, cut section of the left thyroid lobe showed a circumscribed yellow to white 4.2 x 3.9 x 3.1 cm fibrotic nodule with areas of focal hemorrhage (Fig. 2A). The stromal component comprised >90% of the lesion and consisted of fibroblastic/myofibroblastic proliferation, consistent with desmoid-type fibromatosis (Fig. 2B and C). The stromal component extended outside the thyroid with microscopic infiltration into adjacent skeletal muscle (Fig. 2D), and was present at the inked surgical margin. The PTC comprised <10% of the tumor and was confined to the thyroid with negative surgical margins (Fig. 2E). The epithelial component demonstrated characteristic cytological features of PTC, including nuclear enlargement, elongation, grooves, irregular contours, and chromatin pallor (Fig. 2F).
Immunohistochemical staining from the left thyroid tumor. (A) Beta-catenin immunostain, showing aberrant nuclear staining (arrow) in many of the stromal cells (200x magnification). (B) Beta-catenin immunostain, showing aberrant nuclear staining in the stromal cells (arrow). The epithelial (papillary carcinoma) component of the tumor shows membranous staining for beta-catenin without aberrant nuclear localization of the protein (400x magnification). (C). Smooth muscle actin immunostain highlights the stromal component of the tumor (200x magnification). (D) TTF-1 immunostain highlights the PTC nuclei (400x magnification).
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Immunohistochemistry showed aberrant nuclear staining for beta-catenin in stromal cells whereas the epithelial component showed membranous staining for beta-catenin without aberrant nuclear expression (Fig. 3A and B). Stromal cells were positive for smooth muscle actin (Fig. 3C) and desmin (not shown). TTF-1 (Fig. 3D), PAX-8, and cytokeratin (not shown).