An unexpected cervical unicentric Castleman disease disguising as a lymph node metastasis of papillary thyroid carcinoma

Abstract

The onset of cervical lymph nodes could be a turning point in the oncologic management of patients previously treated for differentiated thyroid cancer. Its accurate diagnosis may be challenging. A 56-year-old female patient was diagnosed with papillary thyroid carcinoma (PTC). The initial surgical procedure included total thyroidectomy and prophylactic bilateral central-compartment neck dissection. The pathologic examination featured a 3-centimeter left-sided encapsulated follicular variant of PTC, without vascular invasion nor lymph nodes (LN) metastases. The tumor was staged pT2N0M0 and considered as ATA low risk. We obtained a radioiodine remnant ablation following a cumulative dose of 100 mCi. The response to therapy was excellent: indetectable stimulated thyroglobulin (TgOFF), negative anti-thyroglobulin auto-antibodies (TgAB), and negative imaging. After a 10-year remission, follow-up neck ultrasonography detected solid left-sided lymphadenopathy of level III measuring 86 × 31 mm with slightly concomitant rising TgOFF and positive TgAB, suggesting a possible PTC LN metastasis. The patient underwent surgical resection with favorable outcomes. The recurrence of PTC in the absence of aggressive histological features is unlikely (< 5% of cases). The onset of enlarged cervical lymphadenopathy with biochemical signs of cancer activity in patients with underlying PTC suggests a disease relapse. The pathologic examination revealed a unicentric plasmacytic variant of Castleman disease (UCD), with no evidence of malignancy. Castleman disease (CD) represents a cluster of rare and heterogeneous disorders with distinctive LN histopathological abnormalities. CD can occur in a single LN station [unicentric CD] or involve multiple LN stations with systemic symptoms [multicentric CD]. Mediastinum (29%) and abdominal (21%) sites are the most commonly implicated. Since cervical UCD can potentially mimic PTC lymph metastasis, the distinction between these two conditions is challenging. Only biopsy and histological proof could establish a conclusive diagnosis, allowing appropriate management for each scenario.