Coexistence of Two Different Thyroid Malignancies: A Collision Phenomenon

A patient with a rare co-occurrence of papillary and follicular thyroid carcinomas

The occurrence of papillary and follicular thyroid carcinoma as a collision tumor is rare. We report on a case of a collision tumor consisting of papillary and follicular thyroid carcinoma treated successfully with surgery and radioiodine ablation.

Mixed medullary‑follicular thyroid carcinoma: A case report and literature review

Papillary thyroid cancer (PTC) and medullary thyroid cancer (MTC) originate from follicular and neuroendocrine parafollicular C cells, respectively. PTC and MTC simultaneously exist in tumors containing both MTC and PTC features in a rare condition known as mixed medullary-follicular thyroid carcinoma (MMFTC). In the present study, a 60-year-old female presented with a small mass on the left side of the neck. Ultrasonography indicated a hyperechoic nodule measuring ~11.9×9.7 mm2 in the left lobe of the thyroid gland. The preoperative calcitonin serum value was elevated and total thyroidectomy and bilateral central compartment lymph node dissection was performed. Histological and immunohistochemical analysis of the tumor demonstrated MMFTC. No metastasis was observed in lymph nodes isolated from the bilateral central compartment. Given the rarity of MMFTC, enhancing understanding and management of such tumors is crucial.

Case reports of collision and composite carcinomas of the thyroid: an insight into their origin and clinical significance

BACKGROUND

Collision and composite carcinomas of the thyroid are extremely rare, and their clinical and biological characteristics are poorly understood.

CASE PRESENTATION

The first case was a 41-year-old female patient with a right thyroid nodule. Pathological diagnosis was papillary thyroid carcinoma (PTC) and medullary thyroid carcinoma composite carcinoma. Surgical treatment was right thyroid lobectomy + left partial thyroidectomy + right central neck lymph node dissection. The second case was a 60-year-old female with bilateral thyroid nodules. Total thyroidectomy was performed, and the pathological diagnosis was thyroid collision carcinoma involving follicular thyroid carcinoma on the left side and PTC on the right side. The clinical, histological and gene changes of collision and composite carcinomas of the thyroid are poorly described. With different biological invasion characteristics, the ideal treatment and the prognosis is currently unknown and individualized treatment is necessary.

CONCLUSIONS

It is recommended that in composite carcinoma, each cancer is evaluated and treated according to the most severe tumor. Collision carcinoma should be treated as two separate synchronous primary tumors. For both collision and composite carcinomas of the thyroid, the follow-up after treatment should be extensive.

Collision tumor of a papillary and follicular thyroid carcinoma: a case report

BACKGROUND

Papillary thyroid carcinoma (PTC) and follicular thyroid carcinoma (FTC) are common differentiated thyroid cancers, but the detection of a collision tumor is an extremely rare event.

CASE PRESENTATION

The patient was a 69-year-old Japanese female with multiple cervical lymph node swellings and a thyroid tumor. Preoperative fine needle aspiration cytology of the enlarged lymph node revealed a cytological diagnosis of papillary thyroid carcinoma (PTC). A total thyroidectomy, right cervical dissection and paratracheal dissection were performed. Histopathological and immunohistochemical analyses of resected specimens revealed a collision tumor of PTC and FTC. Multiple metastases of papillary carcinoma were found in the dissected lymph nodes. In the PTC lesion, IHC for BRAF (V600E) was positive but negative for the FTC lesion. Genetic analyses further revealed a TERT promoter C228T mutation in PTC and a NRAS codon 61 mutation in FTC. The patient died of recurrent cancer 8 months after surgery.

CONCLUSIONS

A case of a collision tumor of PTC and FTC is very rare, and even fewer cases have been subjected to genetic scrutiny. The present case was successfully diagnosed by pathological examination using immunohistochemical and genetic analyses. The TERT promoter mutation in the PTC lesion was consistent with the aggressive behavior of the cancer.

Pathologic collision of urinary bladder urothelial carcinoma with small cell carcinoma: a case report

BACKGROUND

Urothelial carcinoma is a major subtype of bladder cancer and small cell carcinoma (SCC) is a rare type of cancer in clinical practice. Pathologic collision of urinary bladder urothelial carcinoma with SCC is not common in clinical settings.

CASE PRESENTATION

Here, we report a patient with high-grade papillary carcinoma which changed to collision tumor with SCC. The patient underwent radical cystectomy; however, neck and mediastinum lymph nodes metastases were detected 11 months after the operation. The lymph nodes were diagnosed pathologically as SCC. Chemoradiotherapy was subsequently prescribed. Unfortunately, this patient died of COVID-19 in early 2023.

DISCUSSION

We hypothesized the mechanism underlying this pathological transformation. For patients with urothelial bladder cancer, pathological analysis should be conducted to allow standardized and persistent treatment. Moreover, drugs should be selected depending on the type of pathology, especially for patients who develop relapse, since collision tumor or other pathological tumors may be present.

CONCLUSIONS

We recommend that radical cystectomy be performed early enough for patients with non-muscle invasive bladder cancer, who are at a high risk of tumor recurrence. However, this conclusion needs to be validated in a larger number of patients.

Collision tumors of the thyroid. A special clinical and pathological entity

Thyroid collision tumors are rare entities that designate two histologically and morphologically distinct tumors that occur simultaneously or as metastases from other organs within the thyroid. Medullary and papillary carcinoma co-occurrence is the most frequent. Several theories tried to explain the pathogenic mechanisms underlining collision tumors, including the theory which assumes that one tumor predisposes the other, stem cell theory, and random effect theory, but their combination better explains the origin of these tumors. Hypotheses about common genetic behavior responsible for the pathogenesis have also been suggested, such as the involvement of germline mutation of RET (Rearranged during Transfection) proto-oncogene in medullary thyroid carcinoma and papillary thyroid carcinoma coexistence, but there is controversy on this topic. Management of thyroid collision tumors is challenging owing to the presence of two distinct tumors with different biological aggressiveness, treatments options, and prognosis, and needs to be individualized.