Synchronous Papillary Thyroid Carcinoma and an Angiomatoid Fibrous Histiocytoma: A Rare, Interesting Case Report

Angiomatoid fibrous histiocytoma (AFH) is an uncommon fibrohistiocytic neoplasm of intermediate malignant potential that most often arises in the subcutaneous tissues of children and young adults. Involvement of the neck is unusual, and its clinical and radiological appearance may overlap with nodal or soft-tissue malignancy. Papillary thyroid carcinoma is the most common thyroid malignancy and commonly presents with suspicious thyroid nodules or cervical nodal disease. We report a 52-year-old man who presented with a gradually enlarging ulcerated left lateral neck mass and a small suspicious left thyroid nodule. Preoperative imaging showed a discrete thyroid lesion and a much larger necrotic lateral neck mass. Fine-needle aspiration of the thyroid nodule was suspicious for a follicular-patterned neoplasm, and the lateral mass was considered most likely to represent metastatic nodal disease. After multidisciplinary review, the patient underwent total thyroidectomy with excision of the lateral neck mass and neck dissection. Final histopathology demonstrated a 1.4-cm classic papillary thyroid carcinoma, staged pT1b pN0, with negative margins and no nodal metastasis. The lateral mass was a well-circumscribed fibrohistiocytic neoplasm with morphological and immunohistochemical features favoring AFH. The case represents the coincidence of having two different pathologies together when a patient presents with a lateral neck mass and thyroid malignancy. This emphasizes the need for an extensive workup for both pathologies separately, rather than taking a neck mass as a sequel of metastasis from thyroid malignancy. AFH has a high incidence of local recurrence, and a small proportion presents with distal metastases; thus, close follow-up is required. At one year, the patient remained clinically well, with no evidence of neck recurrence, undetectable thyroglobulin, and a stable incidental pulmonary nodule. This case illustrates the importance of tissue diagnosis from anatomically distinct lesions when the size or appearance of a presumed metastatic deposit is disproportionate to the primary tumor.