Papillary Thyroid Carcinoma with Spindle Cell Metaplasia: A Rare Encounter

Abstract

A myriad of histological variants of papillary thyroid carcinoma (PTC) have been described, some of which can be diagnostically challenging due to their rarity and overlapping histomorphology with other entities. One of the scarce and poorly characterised variants is PTC with spindle cell metaplasia, of which fewer than 20 cases have been reported in the literature hitherto. Our patient was a 51-year-old woman with a four-month history of painless, gradually enlarging neck swelling. Physical examination revealed a solitary left thyroid nodule. Thyroid ultrasonography demonstrated a hypoechoic nodule with irregular borders and speckles of microcalcification at the periphery. Total thyroidectomy with central and lateral lymph node dissection was performed. Grossly, there was a poorly circumscribed mass occupying the entire left thyroid lobe measuring 30 mm in the largest dimension. Histopathological examination revealed features of a classical PTC. Incidentally, a well-circumscribed 9 mm nodule was identified within the tumour mass. The nodule comprised of spindle cells arranged in loose fascicles, displaying uniform bland looking nuclei. No mitosis, necrosis or nuclear atypia was observed. Immunohistochemically, the spindle cells were immunopositive to TTF-1 and thyroglobulin, indicating thyroid follicular cell lineage. p53 and BRAF V600E mutant protein immunoexpression were focally noted. They were negative for calcitonin, S100, and desmin. Loss of E-cadherin and CK19 were also demonstrated. A diagnosis of PTC with spindle cell metaplasia was rendered. The nature of spindle cell in PTC needs to be meticulously defined. Careful histomorphology examination and judicious use of immunohistochemistry stains are helpful in arriving at an accurate diagnosis.

A sarcomatoid malignancy originating in the right cervical lymph nodes with atypical pathological characteristics: a case report of an incidental finding

“…Meticulous histomorphological examination combined with appropriate IHC staining has long been central to efforts to accurately diagnose solid malignancies ( 19 - 21 ). Leong et al ( 21 ) reported the case of a nodule within a papillary thyroid carcinoma (PTC) exhibiting morphological arrangement as a loose fascicle of spindle cells that was only identified as spindle cell metaplasia in PTC following IHC staining for thyroid transcription factor 1 (TTF-1) and thyroglobulin in those spindle cells, together with the observation of focal p53 and B-Raf serine/threonine kinase (BRAF) V600E mutant protein immunoexpression and the loss of calcitonin, S-100, desmin, E-cadherin, and CK19. This case of PTC with spindle cell metaplasia remains a rare and largely uncharacterized PTC variant.…”

“…Morphological appearance is currently used as an indicator when selecting antibodies for use in IHC staining ( 19 - 22 ). Diagnostic specificity can also be improved through the application of molecular techniques including in situ hybridization, fluorescence in situ hybridization (FISH), gene rearrangement testing, tissue microarrays, and next-generation sequencing ( 19 , 21 - 24 ). In this case, the morphological characteristics observed on initial observation failed to offer sufficient insight into whether this mass was a tumor or a proliferative lesion.…”

Neuroendocrine Carcinoma of the Uterine Cervix With Metastases to the Thyroid Gland: A Case Report and Clinical Pathological Review

“…The histologic appearance of MTC varies and usually consists of sheets and solid nests of round cells with granular eosinophilic cytoplasm and a prominent eccentric nucleus with evenly dispersed chromatin. In some cases, the tumor cells can exhibit marked nuclear pleomorphism, a prominent central nucleolus, and eosinophilic granular cytoplasm, resembling Hürthle cell tumors, while, in other cases, the tumor cells can show prominent nuclear grooves and even inclusions, which can be mistaken for PTC, the most common histological subtype of thyroid carcinoma [6,8].…”