A Case of Diffuse Sclerosing Variant of Papillary Thyroid Cancer: An Aggressive Variant Presenting With Recurrent Locoregional Nodal Disease
Authors: Cruz Yaniris García , Báez Negrón Laisha M , Mangual García Michelle Marie , González Alex N 
Published: May 2021

Abstract
Diffuse sclerosing variant (DSV), a subtype of papillary thyroid carcinoma (PTC), has been considered more aggressive than classical PTC given that it usually presents with extrathyroidal invasion and lymph node metastasis at the time of diagnosis. Data about the risk of recurrence and prognosis is still debatable. Hence, we report a 29-year old woman with recurrent DSV-PTC that presented with pulmonary metastasis after multiple surgical interventions, radioactive iodine (RAI) therapy and a negative whole-body scan (WBS) ten months prior to this finding.
A 29-year old woman without history of systemic illness, family history of thyroid cancer or neck radiation exposure, developed diffuse goiter at age 23. A thyroid and neck ultrasound revealed an enlarged heterogeneous thyroid gland with innumerable small bright echogenicities scattered throughout and bilateral neck adenopathy. No thyroid nodules were seen. Anti-thyroglobulin antibodies (anti-Tg Ab) were positive. A fine needle aspiration biopsy (FNAB) was positive for PTC with cytologic features suggestive of DSV. Subsequently, total thyroidectomy was performed, and 15 lymph nodes were positive for PTC. Thyroid suppression therapy was started maintaining goal of TSH &lt;0.1ng/dL. Patient had a second neck dissection one month later, where 7 lymph nodes were positive for PTC. Pathology revealed chronic lymphocytic thyroiditis with bilateral multifocal PTC and staging pT3N1b. Two months after thyroidectomy, RAI therapy was provided with 153.6mCi of I-131. Post RAI therapy WBS and SPECT/CT demonstrated persistent metastasis to lymph nodes. After this finding, a third left neck dissection was done with additional lymph nodes resection positive for PTC. A second RAI therapy with 138mCi of I-131 was administered the following year. Continued surveillance suggested recurrence of PTC due to new suspicious nodules on neck along with increased anti-Tg Ab level from 44.64 to 95 IU/mL. FNAB confirmed PTC of five different locations of the thyroid bed. She had two additional neck dissections. Metastasis of lymph nodes was confirmed at multiple levels in the right neck and central compartment. Ten months after being without evidence of PTC recurrence in previous WBS and FDG-PET/CT, she started to develop hemoptysis. A neck and chest CT scan demonstrated innumerable bilateral hyperdensities consistent with pulmonary metastasis. At this time, TSH continued suppressed in 0.06 mIU/mL but, anti-Tg Ab had increased to 160 IU/mL.
DSV-PTC has been shown to be at an advanced stage upon diagnosis. Furthermore, it has been documented that distant metastasis could also be present at this time with pulmonary metastasis being the most common. Nonetheless, some authors suggest that the advanced presentation could be due to delayed diagnosis rather than DSV intrinsic behavior. Besides its aggressive nature, DSV-PTC risk of recurrence remains controversial.