Response to the Correspondence Regarding “Cutaneous Metastasis From Papillary Thyroid Carcinoma Eight Years After Initial Surgery”

ABSTRACT

We sincerely thank Dr. Sengul and colleagues for their insightful comments on our case report of skin metastasis in papillary thyroid cancer (PTC). They questioned the adequacy of local excision and suggested completion thyroidectomy to enable radioactive iodine (RAI) therapy or systemic therapy. We appreciate their perspective but explain our rationale, given the exceptional rarity of isolated cutaneous metastasis and limited evidence‐based guidelines. Complete surgical excision may be appropriate for carefully selected patients with solitary cutaneous metastasis, whereas RAI or systemic therapy should be considered according to disease extent, iodine avidity, tumor biology, and patient‐specific factors. We agree that TSH suppression alone does not explain the development of metastasis and that TERT promoter mutations may provide additional insight into the aggressive biological behavior of PTC. Despite the loss of thyroglobulin (Tg) expression in the metastasis, our multimodal surveillance—including ultrasonography and CT—has shown no recurrence, and we will offer functional imaging when clinical indicated. No evidence of recurrent or additional metastatic disease during follow‐up, and per 2025 ATA guidelines, shared decision‐making favored thyroid preservation with close follow‐up. Future disease progression would prompt reconsideration of total thyroidectomy with RAI or targeted therapy.

We sincerely thank Dr. Sengul and colleagues for their thoughtful correspondence regarding our recently published case report [1]. Their comments provide an opportunity to further discuss the diagnostic interpretation and management of this uncommon presentation of papillary thyroid carcinoma (PTC) [2]. We appreciate their constructive observations and are pleased to clarify the rationale underlying our clinical decision‐making.

The correspondents questioned whether local excision alone was sufficient and suggested that completion thyroidectomy should be considered to facilitate radioactive iodine (RAI) therapy and future systemic treatment. We appreciate this perspective. However, we also note that the optimal management of isolated cutaneous metastasis from PTC remains uncertain because of its exceptional rarity. Current guidelines provide limited evidence‐based recommendations for this specific clinical scenario, and treatment decisions therefore rely largely on individualized assessment, multidisciplinary discussion, and the limited published literature. As discussed in our original report, the Japan Association of Endocrine Surgeons guideline [3] does not routinely recommend RAI for metastases to organs other than the lung and bone. Moreover, published case reports [4, 5] suggest that complete surgical excision may be an appropriate option in carefully selected patients, whereas RAI or systemic therapy may be considered when there is additional metastatic disease, iodine‐avid disease, progressive disease, or other clinical indications [6, 7, 8, 9].

We agree that it would be an oversimplification to attribute the development of isolated skin metastasis solely to mildly suboptimal thyroid‐stimulating hormone (TSH) control. Our intention was to emphasize that adequate TSH control remains an important component of long‐term management rather than to imply a direct causal relationship. Tumor progression is likely multifactorial and influenced by intrinsic tumor biology, molecular alterations, and host‐related factors.

We also concur that molecular profiling, particularly assessment of TERT promoter mutations, would have provided additional biological insight. Numerous studies have demonstrated that TERT promoter mutations are associated with aggressive clinicopathological features, distant metastasis, poor prognosis [10, 11], and, when coexisting with BRAF V600E, an increased likelihood of radioiodine‐refractory disease [12, 13, 14, 15]. Unfortunately, TERT testing was not routinely performed when this patient underwent surgery approximately 10 years ago and is still not routinely incorporated into postoperative molecular testing in many institutions in China. Furthermore, accumulating evidence [16] suggests that metastatic lesions may acquire molecular alterations distinct from those present in the primary tumor. Should disease progression occur, molecular analysis of both the primary tumor and metastatic tissue would be considered to guide subsequent management.

We agree that the absence of thyroglobulin (Tg) expression in the metastatic lesion is an intriguing finding. Although Tg is a well‐established marker of thyroid differentiation, loss of Tg expression has been reported in dedifferentiated metastatic PTC and may be associated with a less favorable prognosis [17]. Preservation of the contralateral thyroid lobe inevitably complicates the interpretation of serum Tg levels because residual normal thyroid tissue continues to produce Tg. We recognize that this approach sacrifices some of the diagnostic convenience of Tg surveillance after total thyroidectomy. Nevertheless, in this patient, surveillance has incorporated serial neck ultrasonography, cross‐sectional imaging, and functional imaging when clinically indicated. We believe that this multimodal surveillance strategy provides an acceptable alternative while avoiding the potential morbidity associated with completion thyroidectomy.

At the time of writing, the patient remains free of locoregional recurrence and distant metastatic disease during follow‐up. In accordance with the 2025 American Thyroid Association (ATA) Guidelines [18], treatment decisions should consider not only tumor characteristics but also patient comorbidities, anticipated benefit, quality of life, and patient preferences. Following multidisciplinary discussion and shared decision‐making with the patient, preservation of the remaining thyroid lobe with close surveillance was considered the most appropriate management strategy. Follow‐up includes regular neck ultrasonography, chest and abdominal computed tomography, and additional functional imaging, such as SPECT/CT where clinically appropriate. Should structural recurrence or additional distant metastatic disease develop, completion thyroidectomy and subsequent RAI therapy would be reconsidered according to disease extent and iodine avidity, with molecularly guided systemic therapy considered when appropriate.

Author Contributions

Yi‐Qing Gao: conceptualization, formal analysis, investigation, methodology, visualization, writing – original draft, writing – review and editing. Xin‐Lu Yin: conceptualization, resources, supervision, validation, writing – review and editing. Lu‐Ying Zheng: supervision, validation, visualization, writing – review and editing. Jia‐Dong Wang: conceptualization, methodology, project administration, supervision, validation, writing – review and editing.

Funding

The authors have nothing to report.

Ethics Statement

The authors have nothing to report.

Conflicts of Interest

The authors declare no conflicts of interest.

Data Availability Statement

The data that support the findings of this study are available from the corresponding author upon reasonable request.