Images in endocrine pathology: papillary variant of medullary thyroid carcinoma with cystic change

Encapsulated papillary variant of medullary carcinoma of thyroid with extensive cystic change: an extremely rare presentation

Papillary variant of medullary carcinoma of the thyroid is an unusual subtype with many diagnostic challenges. The authors report a case of papillary variant of thyroid medullary carcinoma in a 37-year-old female, who presented with complaints of pain in the thyroid nodule for the latter two months. Contrast enhanced computed tomography (CECT) neck revealed an enlarged and heterogeneously enhancing left lobe of thyroid. This was followed by hemithyroidectomy for suspicion of colloid goitre. Gross examination of the cut surface of the thyroid parenchyma had a sponge like appearance. On histopathology a diagnosis of encapsulated papillary variant of medullary carcinoma thyroid was made with the help of special stains and immunohistochemistry (IHC).

Pitfalls in Challenging Thyroid Tumors: Emphasis on Differential Diagnosis and Ancillary Biomarkers

Thyroid pathology encompasses a heterogenous group of clinicopathological entities including rare and diagnostically challenging neoplasms. The review is focused on morphological, immunohistochemical, and molecular features of rare thyroid neoplasms that can pose diagnostic problems. The tumors are organized based on growth patterns including thyroid neoplasms with predominantly papillary, follicular, solid, and spindle cell growth pattern, as well as neoplasms with distinct cytological characteristics. A special section is also dedicated to rare thyroid tumors with peculiar patterns including thyroid carcinoma with Ewing family tumor elements and intrathyroidal thymic-related neoplasms.

Do You Know the Details of Your PAX8 Antibody? Monoclonal PAX8 (MRQ-50) Is Not Expressed in a Series of 45 Medullary Thyroid Carcinomas

Medullary thyroid carcinomas display cytologic and architectural features that can simulate various primary and metastatic neoplasms. PAX8 immunoexpression in neuroendocrine neoplasms yielded antibody-dependent findings. Since the data regarding the expression profile of monoclonal PAX8 (MRQ-50) antibody is limited in large series of medullary thyroid carcinomas, this study investigated the expression profile of PAX8 (MRQ-50) in a series of 45 medullary thyroid carcinomas. PAX8 (MRQ-50) expression was noted in the thyroid follicular epithelial cells surrounding the tumor and was negative in all medullary thyroid carcinomas. In addition, twenty medullary thyroid carcinomas showed scattered entrapped thyroid follicular epithelial cells at the periphery of the tumor. Entrapped follicular epithelial cells were positive for PAX8 and thyroglobulin, and were negative for monoclonal CEA and calcitonin. A panel approach combining monoclonal antibodies to transcription factors, hormones and cell-specific peptides often assist diagnosticians in the workup of the cellular origin of a neuroendocrine neoplasm. Since PAX8 immunostaining is dependent on the antibody characteristics in neuroendocrine neoplasms, pathologists should be aware of the details of the PAX8 antibody used in a particular case.

Serum Markers Measured in FNA Fluids of Medullary Thyroid Carcinoma Occurring as a Cyst

Background

Diagnosis of medullary thyroid carcinoma (MTC) is still a challenge, and the measurement of calcitonin in fine-needle aspiration (FNA) washout has been recently introduced. Rarely, MTC presents as a cyst and its preoperative detection is difficult.

Methods

A 66-year-old woman was referred to us with high serum calcitonin. Ultrasound evaluation showed one cystic and one solid nodule. FNA was performed in both nodules and calcitonin, procalcitonin and CEA were measured in the aspirate fluids.

Results

The markers showed elevated levels in the FNA washout of the cyst and the patient was operated on. Final histology demonstrated MTC of the cystic nodule. Four weeks later, all serum markers were undetectable.

Conclusions

In the presence of a cystic thyroid lesion the diagnosis of MTC should be taken into account, and measuring calcitonin in FNA fluid is relevant. The determination in FNA of other markers is technically feasible but its role should be evaluated in larger series.