Rare dual pathology of the neck: synchronous papillary thyroid carcinoma and angiomatoid fibrous histiocytoma—a case report

Introduction: Fibrohistiocytomas are uncommon mesenchymal tumors that typically originate in the dermis or subcutaneous tissue, and are rarely reported in deeper locations, such as bone, retroperitoneum, or the head and neck. Primary thyroid involvement is exceedingly rare, with only sporadic reports of benign and malignant variants. Papillary thyroid carcinoma (PTC) is the most prevalent thyroid malignancy, characterized by distinct nuclear features and well-established cytological criteria. The coexistence of PTC with fibrohistiocytoma within the thyroid region has not been previously described. We report a case of synchronous PTC and fibrohistocytoma, highlighting the diagnostic challenges posed by overlapping clinical and radiological features and underscoring the role of histopathology in guiding management. Case report ; A 52-year-old Asian male patient presented to our clinic with a history of massive neck swelling with a central open wound present for the past 2 months and now increasing in size. The swelling occupied almost the entire neck, and the neck nodes and thyroid gland were not palpable due to the presence of swelling. Further workup showed a suspicious thyroid nodule and neck swelling, which was attributable to metastatic lymph nodes. The thyroid nodule was biopsied and showed papillary thyroid cancer. The case was discussed in a multidisciplinary team meeting, and it was decided to proceed with total thyroidectomy with modified bilateral neck dissection. Histopathology showed two different pathologies: papillary thyroid cancer PT1b and a lateral neck mass. Histopathology of the lateral neck mass revealed fibrohistiocytoma. Conclusion: The case highlights the diagnostic challenges that arise when such tumors are present concomitantly. Lateral neck mass was attributed to be metastatic papillary thyroid cancer rather than a separate pathology, and no pre op biopsy of the mass was taken. When there is a discrepancy between the size of the primary tumor (in our case, a small thyroid papillary tumor) and the metastatic deposit (a large neck mass attributed to metastatic papillary thyroid cancer), separate biopsies should be taken from both regions to confirm the diagnosis. A multidisciplinary approach should be employed to manage this case.