Abstract

Introduction: Medullary thyroid carcinoma (MTC) is a malignant tumor of thyroid gland showing parafollicular or C-cell differentiation. Aims and objectives: The current study was undertaken to evaluate safety of ultrasound-guided thyroid fine-needle aspiration cytology (FNAC) and to assess cytomorphological features of MTC in FNA specimens from 28 patients. Materials and methods: The study was performed by retrospectively reviewing the clinical and pathological records of MTC cases managed at our institute. Results: The patients included 18 males and 10 females with a mean age of 45.3 years; 24 specimens were taken from thyroid, 15 from cervical lymph nodes and one each from liver space occupying lesion and chest wall nodule. There was no complication noted during ultrasound-guided FNAC in these patients. The smears had variable cellularity in the form of moderate cellularity in 63% of specimens and low cellularity in 15% of specimens. Cell arrangements were solid cohesive in 39% of cases and microfollicular clusters in 36% of cases. The frequent microfollicles in two specimens prompted the differential of follicular carcinoma. Dispersed population was noted in 90% of specimens. Binucleated and multinucleated cells were seen in 58 and 53% specimens respectively. Only spindle cell morphology was noted in 2% of specimens. Central to eccentric nuclei were present in 39% of specimens, while 13% of specimens showed mainly eccentric nuclei. In all the specimens, neuroendocrine type of salt and pepper-like morphology was present which is best seen with Papanicolaou (Pap) stain. Similarly, cytoplasm showed granules in 78% and fine vacuoles in 29% of specimens. Amyloid appreciated as flecks or aggregates of amorphous pink or gray color was seen in 37% of specimens. No mitosis was noted in any specimen, while necrosis was seen in only in one specimen. Conclusion: Ultrasound-guided FNAC is a fairly accurate, relatively safe, rapid, and simple tool for preoperative diagnosis of thyroid malignancies. Although the cytological features of MTC are well described, different patterns may pose a diagnostic difficulty.

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