Palliative radiation in primary squamous cell carcinoma of thyroid: a rare case report.

Primary squamous cell carcinoma of the thyroid is an extremely rare neoplasm with aggressive behavior. Until date, only around 60 cases have been reported in the literature. Primary treatment of the patient is radical surgery. With optimum treatment survival is not more than 6 months in this aggressive malignancy. However in our patient surgery it was not possible because of unresectability of the mass due to encroachment of major vessels. Hence, we have delivered radiotherapy alone, with which effective palliation could be achieved and patient is leading a good quality-of-life for last 1 year.

INTRODUCTION

Squamous cell carcinoma (SCC) of the thyroid is an extremely rare disease accounting for less than 1% of all thyroid tumors.[1] In the World Health Organization classification, squamous cell carcinoma thyroid is defined as “SCC of the thyroid should be composed entirely of tumor cells with squamous differentiation.”[2],[3],[4] It is thought to arise from undifferentiated follicular cells, metaplastic follicular epithelium or remnant tissue of the thyroglossal duct. It has a very aggressive course and has dire prognosis. Primary SCC of the thyroid affects older patients (fifth to sixth decade of life) with rapidly increasing thyroid mass with or without cervical lymphadenopathy. Other symptoms include dysphagia, dyspnea and hoarseness of voice due to infiltration of adjacent structures. At the time of diagnosis, these tumors are usually locally advanced with invasion into trachea, esophagus or major vessels. Although the outcome is dismal, aggressive surgery along with adjuvant radiotherapy are recommended in the management of this rare and aggressive cancer for optimum outcome. Here, we are reporting such a rare case of SCC of thyroid who has been treated with palliative radiotherapy.

CASE REPORT

A 70-year-old male patient noticed a rapidly increasing painless mass at the anterior aspect of the left side of neck for 1 month. It was also associated with dysphagia and stridor for 2 weeks. He was a heavy smoker who used to smoke 1 pack of cigarettes/day. There was no history of any previous radiation exposure in the neck. On physical examination, an 11 cm × 7 cm firm lobulated mass was found in the left side of the anterior aspect of the neck. His routine blood investigations and chest X-ray were within the normal limit.

Contrast enhanced computed tomography scan showed evidence of well-defined large, lobulated heterogeneously enhancing solid cystic lesion measuring 11 cm × 8.6 cm × 7.4 cm in relation to the left lobe of thyroid gland. The lesion showed multiple thin intervening septae along with few specks of calcification within it. Posteriorly lesion was extending up to the vertebral column and inferiorly retrosternally up to the brachiocephalic trunk. Mass effect of the lesion was seen in the form of compression and displacement of the trachea toward right and there was also compression and displacement of the left subclavian and carotid vessels, left internal jugular vein and left sternocleidomastoid [Figure 1]. His endoscopy findings were within the normal limit. On positron emission tomography scan, a large multi lobulated heterogeneously enhancing solid-cystic mass (7.8 cm × 7.7 cm × 5.8 cm) was seen in the left side of the neck arising from the left lobe of the thyroid gland with intense fluorodeoxyglucose (FDG) avidity (standardized uptake value max 17.7) in the solid component and along the peripheral margin of the cystic component. The mass was extending into the anterior mediastinum until the level of D4 vertebra and posteriorly until the prevertebral fascia. It was seen to displace the trachea to the right and compressing it [Figure 2]. No FDG avid focus was found in any other part of the body.

Figure 1

Contrast enhanced computed tomography scan showed evidence of well-defined large, lobulated heterogeneously enhancing solid cystic lesion measuring 11 cm × 8.6 cm × 7.4 cm in relation to the left lobe of thyroid gland. The lesion showed multiple thin intervening septae along with few specks of calcification within it. Posteriorly lesion was extending upto vertebral column and inferiorly retrosternally upto brachiocephalic trunk. Mass effect of the lesion was seen in the form of compression and displacement of the trachea toward right and there was also compression and displacement of the left subclavian and carotid vessels, left internal jugular vein and left sternocleidomastoid

Figure 2

Positron emission tomography scan revealed a large multi lobulated heterogeneously enhancing solid-cystic mass (7.8 cm × 7.7 cm × 5.8 cm) was seen in the left side of the neck arising from the left lobe of the thyroid gland with intense fluorodeoxyglucose avidity (standardized uptake value max 17.7) in the solid component and along the peripheral margin of the cystic component

Fine-needle aspiration cytology (FNAC) revealed scattered malignant epithelial cells which showed moderate pleomorphism, high nuclear cytoplasmic ratio, hyperchromatic nuclei and mild to moderate cytoplasm. Large areas of necrosis were also seen. The overall features were those of SCC [Figure 3a and b].

Figure 3

(a) Fine needle aspiration cytology smear shows scattered and cluster of tumor cells with moderately pleomorphic, hyperchromatic nuclei and inconspicuous nucleoli, moderate to abundant cytoplasm. Some of the cells show cytoplasmic keratinization. Occasional fiber cells are also present in a predominantly necrotic background. (b) Photomicrograph showing fiber cell with elongated cytoplasm and hyperchromatic nucleus, characteristic of squamous cell carcinoma

Aggressive treatment in the form of radical surgery was not possible in this particular patient because of its unresectability due to encasement of major vessels. Hence, we delivered palliative radiotherapy 30 Gy in 10 fractions over 2 week's period. Though there was not much regression of the disease, but his pain and shortness of breath was improved reasonably and patient is leading a good quality-of-life for last 1 year.

DISCUSSION

Primary SCC of the thyroid is an extremely rare and aggressive neoplasm. Most of the cases were reported in elderly patients with the presence of local invasion at the time of presentation. The overall prognosis of the tumor is poor with a survival rate of less than a year after the diagnosis.[3],[5],[6] The etiology of this condition is not clear, but hypothesis include the “metaplasia theory” (squamous metaplasia of underlying thyroid disease) and “embryonic-nest theory” (squamous cells originating from remnant ultimobranchial duct or thyroglossal duct) as a result of metaplasia of papillary or follicular cells of the thyroid or from the embryonic remnants with metaplasia of follicular epithelium (thyroglobulin positive variety) (follicular variable). It may also arise as de novo appearance from the follicular cells without metaplasia (thyroglobulin negative variety), which has a worse prognosis.[4],[7],[8] FNAC confirms the diagnosis of SCC, but it is mandatory to exclude SCC that has spread from adjacent upper aero digestive tract sites, as well as metastasis from distant sites, such as the lung, kidney or gastrointestinal tract. The evaluation therefore usually involves a combination of endoscopy and radiographic examination by computed tomography to rule out the neighboring or metastatic carcinoma.[4],[9] In our patient, we could not perform biopsy because there was encasement of major vessels and the diagnosis was confirmed by FNAC only. We have excluded the possibility of the tumor arising from an adjacent structure such as the esophagus or representing a metastasis from a primary growth elsewhere, by different investigative procedures.

In several reports based on small series of patients with SCC of the thyroid, the recommended treatment was an early diagnosis and combining the best available therapeutic modalities with extensive surgery.[3],[10] However, the success rate of radical surgery was compromised by the invasive nature of the tumor and a poor definition of surgical treatment. Cook et al. described optimal surgical therapy as hemithyroidectomy or total thyroidectomy, depending upon the multifocality, followed by radiotherapy. The addition of post-operative radiotherapy could lead to improved loco-regional control.[11] Until date, chemotherapy has not been shown to be of benefit in this condition. Simpson and Carruthers[3] noted no benefit in two patients treated with adriamycin nor in another treated with 5-fluorouracil and mitomycin, while Shimaoka and Tsukada[10] failed to achieve a response in three patients treated with nitrogen mustard, vincristine and AB-132, respectively. Cisplatin has been shown to have benefited patients suffering from other squamous cell cancers of the head and neck but, to date, no information is available on its use in SCC of thyroid.

Even after optimum treatment, this aggressive malignancy has very dire prognosis with dismal outcome.

In this kind of deadly disease, where survival is not expected to be more than 1 year, quality-of-life is very important. In this particular situation, though we were not able to deliver optimum treatment to the patient, but we could achieve effective palliation with radiotherapy alone and gift patient a good quality-of-life.