|Year : 2018 | Volume
| Issue : 5 | Page : 1142-1144
Poorly differentiated carcinoma of thyroid: Case report of an uncommon entity
Shaan Khetrapal, Safia Rana, Sujata Jetley, Zeeba Jairajpuri
Department of Pathology, Hamdard Institute of Medical Sciences and Research, New Delhi, India
|Date of Web Publication||7-Sep-2018|
Department of Pathology, Hamdard Institute of Medical Sciences and Research, Hamdard Nagar, New Delhi - 110 062
Source of Support: None, Conflict of Interest: None
Malignant thyroid tumors of follicular origin comprise a spectrum, with the indolent well-differentiated thyroid carcinoma (WDTC) at one end and lethal anaplastic thyroid carcinoma (ATC) at the other. Poorly differentiated thyroid carcinoma (PDTC) lies intermediately between WDTC and ATC in terms of morphology and prognostic standpoint. This thyroglobulin producing neoplasm accounts for 4–7% of all thyroid malignancies. PDTC has been controversial due to lack of defined diagnostic criteria. We hereby report a case of PDTC in a 42-year-old female presenting with neck swelling, pain, and dysphagia for 10 months. She was diagnosed as colloid goiter on fine-needle aspiration cytology. On imaging, a large complex thyroid with central neck nodes was seen. Total thyroidectomy and central neck node dissection were done. Based on the morphology, immunostaining, and the diagnostic criteria, a diagnosis of PDTC was made. PDTC is a diagnostic challenge due to its rarity and previous equivocal diagnostic criteria.
Keywords: Carcinoma thyroid, poorly differentiated, thyroglobulin
|How to cite this article:|
Khetrapal S, Rana S, Jetley S, Jairajpuri Z. Poorly differentiated carcinoma of thyroid: Case report of an uncommon entity. J Can Res Ther 2018;14:1142-4
| > Introduction|| |
Poorly differentiated thyroid carcinoma (PDTC), an uncommon thyroglobulin, producing neoplasm accounts for 4–7% of all thyroid malignancies. The term PDTC was first coined by Sakamoto et al. in 1983. It gained recognition after inclusion in the WHO classification of endocrine tumors in 2004. Lately in 2006 after the consensus meeting in Turin, Italy regarding the diagnostic criteria, this rare malignancy has been acknowledged as a distinct pathological entity. We hereby report a rare and interesting case of PDTC.
| > Case Report|| |
A 42-year-old female presented with neck swelling, gradually increasing in size, with pain and mild dysphagia for 10 months. On examination, a diffuse midline neck swelling nontender and hard in consistency was seen. A diagnosis of colloid goiter was made on fine-needle aspiration cytology (FNAC) at one center. Computed tomography scan showed large complex thyroid with central neck nodes. The patient then came to our center with persistent clinical complaints. On repeat FNAC, lymphocytic thyroiditis was the diagnosis. Surgery was advised due to the compression symptoms and the retrosternal extension. Total thyroidectomy and central neck node dissection were planned. On gross, the specimen thyroid measured 5.5 cm × 4 cm × 1 cm. Cut section was grayish white with few colloid cysts of 1 cm each were seen [Figure 1]. Multiple lymph nodes ranging in size from 0.5 to 1.2 cm in diameter were also received. Microscopically, normal areas of thyroid admixed with nodular growth were seen comprising sheets and nests of large atypical cells exhibiting marked pleomorphism, high N/C ratio, mitosis, and prominent nucleoli [Figure 2], [Figure 3], [Figure 4]. Peritheliomatous growth pattern was focally present [Figure 5]. Vascular and neural invasion along with large areas of necrosis in the intervening stroma were seen. Focal areas of colloid-filled follicles with low cuboidal epithelium and collections of mononuclear cells were seen. The tumor was extending beyond the capsule into the adjacent soft tissue, and 4/8 lymph nodes were positive for tumor deposits. Immunohistochemistry (IHC) for thyroglobulin was positive. Thus, based on the morphology, immunostaining, and diagnostic criteria, a diagnosis of PDTC was made.
|Figure 1: Gross photograph of cut section poorly differentiated thyroid carcinoma showing a grayish white tumor with a solid appearance and focal collection of colloid|
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|Figure 2: Microphotograph showing normal thyroid along with tumor area (H and E, ×10)|
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|Figure 3: Microphotograph showing nodular growth pattern comprising solid nests of follicular cells (H and E, ×10)|
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|Figure 5: Microphotograph showing sheets and nests of large atypical cells (H and E, ×40)|
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| > Discussion|| |
Malignant tumors of thyroid comprise a spectrum, with the indolent well-differentiated thyroid carcinoma (WDTC) comprising papillary and follicular carcinoma at one end and lethal anaplastic thyroid carcinoma (ATC) at the other. PDTC lies intermediately between WDTC and ATC in terms of morphology, behavior, and prognostic standpoint.,
The etiology of PDTC is suggested to have a genetic and environmental basis including dietary factors explaining the higher prevalence in regions such as northern Italy and Central Europe.
Clinically, PDTC has been seen to have a frequent association with long-standing goiter. They present as large, rapidly growing mass presenting in the fifth decade. At the time of diagnosis, they tend to present as an advanced disease with a tendency of local recurrence and metastases. Various studies have different observations regarding sex predilection; two studies were seen to have a female predominance., However, in this case, the patient presented at an earlier age than documented and was previously diagnosed as colloid goiter on FNAC. Repeat FNAC at our institute showed mature lymphocytes infiltrating thyroid follicles, and hence, a diagnosis of lymphocytic thyroiditis was made. Thus, the dilemma remains, whether PDTC developed in a long-standing goiter or was it a diagnostic pitfall encountered on cytology. The diagnosis of PDTC on cytology is problematic due to its rarity, subtle cytological findings, and lack of experience.
In majority of cases, the macroscopic features are typically same including a large size >4 cm in 50% cases, incomplete tumor capsule, pushing borders, and extension into the adjacent soft tissues. The cut surface is gray to white, firm along with macroscopic evidence of necrotic foci at times., The findings being classically present in this case.
There had been controversies regarding PDTC due to lack of defined diagnostic criteria. According to the WHO classification 2004, the diagnosis relied on architectural pattern including insular, trabecular, and solid in an otherwise malignant thyroid lesion. It also included infiltrative growth pattern, necrosis, increased mitosis as other high-grade features along with mild cytologic atypia. However, what came out alarming was that the solid, trabecular, insular patterns can commonly occur admixed within the same lesion and are even seen to coexist with differentiated components of the papillary and follicular types., Thus, extensive sampling and meticulous microscopic examination are imperative to establish an accurate histological diagnosis. The literature reviewed consists of numerous studies regarding the high-grade features such as the presence of necrosis and high mitotic activity as parameters shown to have an association with adverse prognosis and therefore their inclusion as a hallmark feature in diagnosis of PDTC. Necrosis varies from case to case being extensive, peritheliomatous, or punctate. Thus, concluding that these criteria of the WHO were difficult to apply and had overlaps in categories. A consensus meeting in Turin, Italy came up with the “Turin proposal,” a schematic approach with diagnostic criteria for practical use:
- Presence of a solid/trabecular/insular pattern of growth
- Absence of the conventional nuclear features of papillary carcinoma and
- Presence of at least one of the following features: Convoluted nuclei, mitotic activity ≥3 × 10 high-power field, and tumor necrosis.
According to the above-mentioned criteria, the diagnosis of PDTC can purely be made on morphology. These microscopic criteria were met in the present case. IHC for thyroglobulin was also strongly positive, thus excluding the diagnosis of ATC. PDTC is a follicular thyroid epithelium-derived tumor, found to have expression for thyroglobulin and thyroid transcription factor-1 acting as an add-on in confirmation of this diagnosis. Thyroglobulin serum levels have also been useful in postoperative follow-up.,,
The prognosis rates among WDTC, PDTC, and ATC are statistically different. The prognosis for PDTC is worse than WDTCs but is better than ATCs, having a mean 5-year survival in 50% of patients. Therefore, a timely diagnosis before metastases and subsequent surgery can be highly advantageous.
| > Conclusion|| |
PDTC is a diagnostic challenge due to its rarity and previous equivocal diagnostic criteria. It is therefore important to ascertain, differentiate, and recognition of this histologic variant for appropriate management and better prognosis.
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Conflicts of interest
There are no conflicts of interest.
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