Indian Journal of Pathology and Microbiology

CASE REPORT
Year
: 2018  |  Volume : 61  |  Issue : 2  |  Page : 242--244

Sclerosing mucoepidermoid carcinoma with eosinophilia of thyroid gland: Not so indolent a neoplasm?


Anila Kunjulekshmi Amma Raveendran Nair1, Nebu A George2, Rejnish Kumar3, A Sreekumar4, K Jayasree1,  
1 Department of Pathology, Regional Cancer Centre, Thiruvananthapuram, Kerala, India
2 Department of Surgical Oncology, Regional Cancer Centre, Thiruvananthapuram, Kerala, India
3 Department of Radiotherapy, Regional Cancer Centre, Thiruvananthapuram, Kerala, India
4 Department of Nuclear Medicine, Regional Cancer Centre, Thiruvananthapuram, Kerala, India

Correspondence Address:
Anila Kunjulekshmi Amma Raveendran Nair
Department of Pathology, Regional Cancer Centre, Thiruvananthapuram - 695 011, Kerala
India

Abstract

A 58-year-old female, a known diabetic and hypertensive, presented with left-sided swelling on the anterior aspect of the neck of 1-year duration, which was rapidly increasing in size for the past 6 months. She was on Eltroxin for hypothyroidism for the past 1 year. Computed tomography study of the neck showed a nodule in the left lobe of thyroid which on fine-needle aspiration was suspicious for malignancy. Total thyroidectomy with left posterolateral lymph node dissection was done. Histopathological examination showed sclerosing mucoepidermoid carcinoma with eosinophilia (SMECE) of the thyroid gland with lymph node metastasis. SMECE of the thyroid was initially thought to be a low-grade malignancy with indolent clinical behavior. However, our case showed extra thyroidal spread with lymph node metastasis, necessitating adjuvant therapy for our patient. Such aggressive behavior has been noted in few earlier case reports also.



How to cite this article:
Raveendran Nair AK, George NA, Kumar R, Sreekumar A, Jayasree K. Sclerosing mucoepidermoid carcinoma with eosinophilia of thyroid gland: Not so indolent a neoplasm?.Indian J Pathol Microbiol 2018;61:242-244


How to cite this URL:
Raveendran Nair AK, George NA, Kumar R, Sreekumar A, Jayasree K. Sclerosing mucoepidermoid carcinoma with eosinophilia of thyroid gland: Not so indolent a neoplasm?. Indian J Pathol Microbiol [serial online] 2018 [cited 2020 Apr 2 ];61:242-244
Available from: http://www.ijpmonline.org/text.asp?2018/61/2/242/230536


Full Text



 Introduction



Sclerosing mucoepidermoid carcinoma with eosinophilia (SMECE) of the thyroid was first described by Chan et al. in 1991.[1] It is characterized by nests or strands of epidermoid neoplastic cells with squamous differentiation and areas of glandular differentiation with rare mucous cells in a prominent sclerotic stroma with dense eosinophilic and lymphocytic infiltration. Almost all these cases are associated with chronic lymphocytic (Hashimoto) thyroiditis. This is a distinct entity which has to be differentiated from mucoepidermoid carcinoma of the thyroid as well as other thyroid malignancies which can show squamous differentiation such as papillary carcinoma, medullary carcinoma, and anaplastic carcinoma. Primary squamous cell carcinoma of thyroid though rare and squamous cell carcinoma of adjacent structures infiltrating thyroid should also be considered in the differential diagnosis. However, the distinct squamous cell nests including keratinized ones, glandular pattern, and mucus cells with characteristic sclerotic stroma with the background showing eosinophils are diagnostic. Like other thyroid disorders, this entity is also more common in females. However, there are few case reports in the literature, wherein SMECE occurred in male patients.

 Case Report



A 58-year-old female who was a known diabetic and hypertensive on medication presented to our outpatient clinic with complaints of swelling in the anterior aspect of the neck. She was on tablet Eltroxin for hypothyroidism for the past 1 year. She gave a history of swelling anterior aspect of the neck for the past 1 year, which was increasing in size for the past 6 months with associated difficulty in deglutition. On examination, there was a firm-to-hard mass on the anterior aspect of the neck more towards the left, moving with deglutition.

Computed tomography (CT) neck showed a nodule measuring 4.8 cm × 2.5 cm × 2.3 cm in the left lobe of thyroid displacing trachea to the right of midline, with tracheoesophageal groove extension. Left level III lymph node measuring 25 mm × 15 mm × 13 mm and left paratracheal node measuring 8 mm × 6 mm were also picked up in CT. Nasopharyngeal laryngoscopy showed left vocal cord palsy and mucosal bulge in trachea. Fine-needle aspiration was done which was reported as suspicious for malignancy. The patient was taken up for surgery.

Per- operatively, there was a 5 cm × 3 cm nodule involving the entire left lobe with extension into tracheoesophageal groove. Right lobe and isthmus appeared normal. Total thyroidectomy with left posterolateral neck dissection was done. The tumor had to be shaved off from the esophagus and only an R1 resection could be achieved. Gross specimen that we received showed thyroidectomy specimen with an enlarged left lobe. On cut section, there was a firm-to-hard gray-white growth measuring 5 cm × 3 cm involving entire left lobe with the involvement of thyroid capsule [Figure 1]. Right lobe and isthmus appeared normal.{Figure 1}

Microscopy showed a neoplasm composed of small irregular nests and anatomizing strands of epidermoid cells and glandular structures in a sclerotic stroma with the background showing dense eosinophilic infiltration along with lymphocytes and plasma cells [Figure 2]a. Well-formed squamous pearls were also noted [Figure 2]b. Interspersed with the epidermoid cell nests were noted mucous secreting cells and small mucin pools [Figure 2]c. The cells lining the glandular spaces showed moderate amount of clear/eosinophilic cytoplasm and vesicular nucleus. The neoplasm was seen to infiltrate the thyroid capsule with extrathyroidal spread. Left level III node showed metastasis. The metastatic component comprised predominantly of epidermoid cells in nests and cords with dense eosinophilic infiltration [Figure 2]d. Immunohistochemistry (IHC) showed positive staining with thyroglobulin and thyroid transcription factor-1 (TTF-1) in both epidermoid and glandular areas [Figure 3]a and [Figure 3]b. However, the positivity for these antibodies in epidermoid areas were much weaker as compared to the glandular areas. Mucin stain done highlighted intracellular as well as extracellular mucin. A diagnosis of SMECE of thyroid with metastasis to left level III node was given.{Figure 2}{Figure 3}

 Discussion



SMECE of thyroid is a rare malignant neoplasm showing epidermoid and glandular differentiation accompanied by prominent sclerosis and by eosinophilic and lymphocytic infiltration. SMECE of thyroid was first reported by Chan et al. in 1991, as a low-grade malignancy in thyroid gland occurring in a background of Hashimoto thyroiditis. Since then, a few cases of this rare malignancy have been reported in the literature.

SMECE is almost exclusively seen in women and is usually associated with lymphocytic thyroiditis. However, very few case reports of this entity in male patients have also been reported.[2] The SMECE of thyroid gland most commonly presents as painless neck mass or cold nodule on thyroid scan. Nonspecific symptoms such as hoarseness of voice and difficulty in deglutition occur depending on extension of tumor and compression or infiltration of adjacent structures. The histogenesis of these tumors was a matter of controversy with some authors suggesting that these tumors develop from ultimobranchial body rests/solid cell nests, others reported a follicular origin. Few authors also suggested an origin from C-cells, parathyroid, ectopic salivary gland, and thyroglossal duct.[3],[4] However, another concept is that these tumors arise from follicular epithelium-derived metaplastic squamous nests that occur in a setting of Hashimoto or lymphocytic thyroiditis.[5],[6] However, recent molecular analysis study by Shah et al. on nine cases of SMECE showed cases to be negative for mutations and translocations commonly involved in thyroid carcinogenesis. Their study also showed negativity for MAML2 translocation which is usually positive in mucoepidermoid carcinoma of the salivary gland. Thus, Shah et al. concluded that SMECE appears molecularly and morphologically distinct from follicular and C-cell-derived thyroid tumors as well as from salivary gland mucoepidermoid carcinoma.[7]

SMECE should be differentiated from thyroid tumors that can show foci of squamous differentiation and also from the rare primary squamous carcinoma of the thyroid. Thyroid tumorswith areas of squamous differentiation include papillary carcinoma, medullary carcinoma, and anaplastic carcinoma. The dense eosinophilic infiltrate which is characteristic of this entity is, however, absent in all the other conditions. Papillary carcinoma can be differentiated from SMECE by its characteristic nuclear morphology. Medullary carcinoma with areas of squamous and mucinous change, along with its sclerotic amyloid-rich stroma can mimic SMECE. Positive staining with calcitonin in medullary carcinoma will differentiate medullary carcinoma from SMECE. Primary squamous cell carcinoma of thyroid is rare. The morphologically is similar to squamous cell carcinomas of other organs. However, lack of the glandular component as well as background thyroiditis and eosinophilia help in differentiating this from SMECE. The nodal metastasis of SMECE with prominent eosinophils and sclerosis can be mistaken for Hodgkin's lymphoma.[8]

IHC in this entity in different case reports showed variable results with thyroglobulin and TTF1, with some studies showing negative staining while some cases showed positive results.[9] In this case, we observed positive staining with thyroglobulin and TTF1 in both epidermoid and glandular areas. However, the positivity for these antibodies in epidermoid areas was much weaker as compared to the glandular areas. Furthermore, SMECE is rather a morphological diagnosis, and IHC is required only when classical features are absent.

SMECE of thyroid was initially thought to be a low-grade malignancy with indolent clinical behavior. However, cases with extra thyroidal extension, distant metastasis, and lymph node metastasis have been reported.[9] Early literature shows that in spite of extra thyroidal extension and regional recurrence the survival was good.[10] However, in a recent study by Quiroga-Garza et al. 5 of 6 patients had died within 1.5–8 years after initial diagnosis, 3 of them had distant metastasis, although definite cause of death was not documented.[10],[11]

 Conclusion



The behavior of SMECE of thyroid gland may be more aggressive than we thought; and hence, more data regarding follow-up of this rare malignant entity is required for better understanding of this entity. Our patient had an uneventful postoperative period, and considering that only R1 resection was achieved, she is currently being given radiotherapy.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

References

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