Poorly differentiated thyroid carcinoma with rhabdoid phenotype: a diagnostic dilemma--report of a rare case

Anaplastic thyroid carcinoma with rhabdoid phenotype: An unusual case and a comprehensive review

Anaplastic thyroid carcinoma (ATC) is a highly aggressive thyroid malignancy predominantly affecting the elderly with a fatal outcome. ATC with rhabdoid phenotype is a rare variant, with only a few cases reported in the literature to date. We herein report a case of a 44-year old female diagnosed as ATC with rhabdoid phenotype. She had a slow-growing neck mass with no gross extrathyroidal extension (ETE) or nodal/distant metastasis at presentation. Computed tomography of the neck showed a well-defined heterogeneously hypodense nodule in the right lobe of the thyroid. On cytology, a diagnosis of papillary thyroid carcinoma (PTC) with possible anaplastic transformation was made based on the presence of vague papillae with focal nuclear features of PTC and atypical pleomorphic/rhabdoid cells. The total thyroidectomy specimen showed a relatively circumscribed lesion with no gross ETE. Histopathological examination revealed sheets of rhabdoid cells with a focus of poorly differentiated thyroid carcinoma. On immunohistochemistry, rhabdoid cells were positive for AE1/AE3, focally positive for PAX8 and were negative for TTF-1, synaptophysin, desmin, myogenin, S100P, and SMA. The neck lymph nodes were non-metastatic. The patient was further treated with adjuvant radioactive iodine. Four-months post-operatively, the patient developed pulmonary metastasis which on biopsy examination revealed metastatic ATC. Apart from being a rare tumor type, this case is unusual with its presentation too; wherein, unlike described earlier in the literature the patient had a relatively mitigated clinical course with no gross ETE or nodal/distant metastatic disease. We also review the relevant literature along with this case.

SMARCB1 (INI1)-deficient thyroid carcinoma: A novel entity expanding the spectrum of tumors with INI1 loss

BACKGROUND

Biallelic loss of SMARCB1/INI1 is associated with highly aggressive malignancies, namely renal and extra-renal malignant rhabdoid tumors, and atypical teratoid/ rhabdoid tumor. Increasing availability of molecular testing and immunohistochemical stains acting as surrogate tools to genetic analysis has led to an increasing recognition of SMARCB1 loss in a variety of neoplasms. Interestingly, many of these lack the typical rhabdoid features ascribed to this group of tumors, making their identification difficult.

CASE PRESENTATION

We describe the cytological, histological, immunohistochemical and molecular features of the first case of primary SMARCB1 (INI1)-deficient carcinoma of the thyroid gland in literature. The tumor was unique in various aspects; apart from never having been documented at this location, it showed extensive glandular differentiation, mimicking metastatic adenocarcinoma.

CONCLUSION

Awareness of this novel entity is essential to avoid misdiagnosis, and for appropriate management, especially in an era of increased feasibility of targeted therapy.

Primary mucinous carcinoma of thyroid gland with prominent signet-ring-cell differentiation: a case report and review of the literature

Purpose

This study reports a case of primary mucinous carcinoma of the thyroid gland with signet-ring-cell differentiation, and reviews the literature to evaluate its real incidence and the prognosis of these patients.

Patients and methods

A 74-year-old Chinese woman, presenting with a mass in the right lobe of thyroid gland, came to the hospital. Computed tomography revealed a mass in the right lobe of the thyroid gland, accompanied with right neck lymphadenectasis and airway deviation caused by tumor compression. Thyroid imaging suggested a thyroid malignant tumor and suspicious lymph node metastasis. Histologically, the tumor was characterized by the tumor cells arranged in small nests or trabeculae with an abundant extracellular mucoid matrix. The tumor cells formed diffuse invasion among thyroid follicles. In the peripheral regions, prominent signet-ring-cells formed a sheet-like structure and extended into the extrathyroidal fat tissue. The tumor cells were diffusely positive for thyroid transcription factor-1 (TTF-1) and PAX8, while they were focally positive for pan-cytokeratin (AE1/AE3) and weakly expressed thyroglobulin.

Results

Based on the histological features and immunohistochemical profile, a diagnosis of primary mucinous carcinoma of the thyroid gland with signet-ring-cell differentiation was rendered.

Conclusion

Using a panel of immunohistochemical markers may be helpful for differential diagnosis and for determining whether the tumor is primary or not.

Primary mucinous carcinoma with rhabdoid cells of the thyroid gland: a case report

Background

Primary mucinous carcinoma of the thyroid gland is a rare disease; only 6 cases of primary mucinous carcinoma of the thyroid have been previously reported. Primary mucinous carcinoma of the thyroid gland with incomplete tumor resection tends to be associated with a poor prognosis, resulting in death within a few months. An early and appropriate diagnosis may contribute to improvement in patient prognosis; however, it is extremely difficult to diagnose primary mucinous carcinoma of the thyroid. We present the seventh reported case of primary mucinous carcinoma in the thyroid gland; moreover, rhabdoid cells were detected, which, to our knowledge, is a novel finding.

Case presentation

An 81-year-old Japanese woman was initially diagnosed with a poorly differentiated thyroid carcinoma, and she underwent a hemithyroidectomy. Pathological examination revealed the presence of abundant mucus and agglomeration of large atypical cells. Rhabdoid cells were also seen scattered among the tumor cells. Immunostaining was performed for various markers, and on the basis of these results, we diagnosed the lesion as primary mucinous carcinoma with rhabdoid cells in the thyroid gland. Ten months after surgery, recurrence was noted in the paratracheal lymph nodes; therefore, total resection of the residual thyroid gland and paratracheal lymphadenectomy with thyroid-stimulating hormone suppression were performed. The patient is currently alive and disease-free.

Conclusions

The current case is of interest not only because of the rare histological findings, but also because the patient achieved long-term survival following diagnosis of a mucinous carcinoma. We believe this report will be helpful for diagnosing future cases of mucinous carcinoma of the thyroid.

Anaplastic thyroid carcinoma with rhabdoid features

Anaplastic thyroid carcinoma (ATC) is a rare, highly aggressive neoplasm, characterized by complete or partial composition by undifferentiated cells. We report a case of ATC with rhabdoid features in a 68-year-old male, who presented with a rapidly enlarging neck mass. Fine-needle aspiration (FNA) of the thyroid mass showed discohesive, pleomorphic round to polygonal rhabdoid cells with one to multiple eccentric, large, rounded nuclei with a prominent nucleolus, moderate to abundant, globoid cytoplasm which oftentimes harbor a pale para-nuclear inclusion. The cytoplasm of some cells contained variously sized, eosinophilic granules. Rare cells contained neutrophils in their cytoplasm. Mitoses including atypical mitotic figures and necrosis were readily seen. Histologic examination of needle core biopsy (NCB) revealed individual dispersed and sheets of pleomorphic neoplastic cells with similar cytomorphologic features as described above. The tumor extensively infiltrated a myxocollagenous stroma containing lymphocytes and neutrophils, and demonstrated foci of necrosis. Tumor cells were immunoreactive for keratins AE1/AE3, CAM5.2, and CK19; PAX-8, and p63, but negative for S-100, HMB-45, calcitonin, TTF-1, thyroglobulin, CD56, HBME-1, glypican-3, PAX-5, myogenin, CD31, and INI-1. The differential diagnosis of this malignant rhabdoid tumor is discussed.

Unusual tumors of the thyroid gland

Thyroid neoplasms are classified into three major categories: epithelial, nonepithelial, and secondary. Most primary epithelial tumors of thyroid are derived from follicular cells. These include follicular adenoma and carcinoma (Hürthle and non-Hürthle), and papillary carcinoma and its variants. Other primary epithelial tumors include medullary carcinoma, mixed medullary and follicular carcinomas, insular and poorly differentiated carcinoma, anaplastic carcinoma, and the least common squamous carcinoma and related tumors. The nonepithelial tumors are rare; the most common include malignant lymphoma and tumors arising from the mesenchymal elements. The secondary tumors represent metastatic tumors to the thyroid usually originating in lung, kidney, and breast. In this article, the authors review the unusual tumors of the thyroid, their morphologic features, and clinical and prognostic implications.

Anaplastic thyroid carcinoma with rhabdomyoblastic differentiation: a case report with a good clinical outcome

Anaplastic thyroid carcinoma is a rare and highly malignant disease. Usually, this type of tumor is irresectable, and almost all patients die within 1 year after diagnosis. We present a case of anaplastic thyroid carcinoma with rhabdomyoblastic differentiation and good therapeutic outcome. A 76-year-old female was referred to our hospital with a growing, painless neck mass which existed for 3 months. Biopsy of the mass showed microscopically and immunohistochemically a follicular (Hürthle cell) carcinoma of the thyroid, dedifferentiated to an anaplastic carcinoma with divergent differentiation along rhabdomyoblastic cell lines. The patient underwent a total thyroidectomy with additional lymph node dissection, followed by two episodes of 150 mC I(131) therapy and external radiotherapy. After a follow-up of 3 years, the patient still remains in a good condition without any signs of recurrent disease. Other cases of rhabdomyoblastic and rhabdoid anaplastic thyroid carcinomas have been described. Both types of carcinoma are associated with an aggressive clinical course. In our case, the patient is still alive without evidence of disease 3 years after primary therapy. The good clinical outcome of our patient suggests that surgical resection, radiotherapy, and I-131 ablation therapy with curative intent seems to be an adequate treatment option in patients with anaplastic thyroid carcinoma with rhabdoid and rhabdomyoblastic differentiation.