This rare tumor has a distinct morphology mimicking the same tumor found in the salivary glands. It has a similar microscopic appearance with squamous epithelial cells mixed with mucin producing cells. Overall, there is a good prognosis with occasional cases metastasizing to regional lymph nodes and rarely with distant metastases.
To make a rare tumor even more distinctive, there is a variant known as a sclerosing mucoepidermoid carcinoma with eosinophilia, which arises in patients with fibrosing Hashimoto's disease. The addition of eosinophils and fibrosis makes this variant distinctive. It, too, may metastasize to regional lymph nodes and show extracapsular spread.
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CHARACTERIZATION GENERAL Sclerosing mucoepidermoid carcinoma with eosinophilia of the thyroid: report of two patients, one with distant metastasis, and review of the literature.
Sim SJ, Ro JY, Ordonez NG, Cleary KR, Ayala AG.
Department of Pathology, The University of Texas M. D. Anderson Cancer Center, Houston 77030, USA.
Hum Pathol. 1997 Sep;28(9):1091-6. Abstract quote
Sclerosing mucoepidermoid carcinoma with eosinophilia (SMECE) is a recently recognized malignant neoplasm of the thyroid gland. Two additional cases of this condition which occurred in a 70-year-old woman and a 69-year-old woman are presented.
The case of the 70-year-old woman (patient 1) is the first report of distant metastasis, besides lymph node metastasis, for this type of tumor. The patient initially presented with a thyroid mass, and the thyroid gland with surrounding cervical lymph nodes was removed. Because of focal keratin "pearl" formation, the tumor was misinterpreted as a metastatic squamous cell carcinoma to the thyroid. Approximately 4 years later, the patient developed a left supraclavicular mass and lung densities. A pathological fracture of the right humeral head followed, and the left supraclavicular mass recurred along with newly developed subcutaneous nodules on the chest wall and arm. Open lung and bone biopsies revealed metastatic SMECE, which was morphologically identical to that of the thyroid mass. The 69-year-old woman (patient 2) had, in 1983, undergone thyroidectomy with left radical neck dissection; this had been diagnosed as follicular carcinoma of the thyroid with lymph node involvement. After multiple isolated lymph nodes metastases, the patient developed locally extensive, recurrent tumor that showed microscopic features of SMECE. Review of the previous thyroid tumor and lymph nodes revealed the same type of histology.
To our knowledge, only a single report containing eight cases of this distinctive carcinoma of the thyroid has been published. Herein we describe characteristic morphological features of two additional cases of this rare malignancy, one with distant metastasis, and we review the related literature.
HISTOLOGICAL TYPES CHARACTERIZATION GENERAL The cytomorphologic features of sclerosing mucoepidermoid carcinoma of the thyroid gland with eosinophilia.
Geisinger KR, Steffee CH, McGee RS, Woodruff RD, Buss DH.
Department of Pathology, Wake Forest University and the Baptist Hospital Medical Center, Winston-Salem, North Carolina, USA.
Am J Clin Pathol. 1998 Mar;109(3):294-301. Abstract quote
Sclerosing mucoepidermoid carcinoma with eosinophilia (SMECE) is a recently described carcinoma of the thyroid gland associated with Hashimoto's thyroiditis and considered to have a relatively indolent clinical course.
We describe two patients with SMECE and its aspiration and exfoliative cytologic features. Patient 1 was a 39-year-old woman with a goiter for many years. Examination of the lobectomy specimen revealed SMECE associated with Hashimoto's disease; 4 months later a total thyroidectomy was performed, metastases were found in nine lymph nodes in the neck. Two years later, fine-needle aspiration biopsy (FNAB) of a paritracheal mass revealed recurrent tumor. After 2 more years, two pleural fluid samples contained metastatic carcinoma with eosinophils. Patient 2 was a 61-year-old man with thyromegaly and vocal cord paralysis. The FNAB revealed a poorly differentiated carcinoma. The subsequent thyroidectomy demonstrated SMECE. Two years later, an FNAB of a vertebral mass demonstrated metastatic mucoepidermoid carcinoma.
In all specimens, malignant cells with definite glandular and squamoid differentiation were present in small cohesive aggregates; eosinophils associated with the tumor cells were present in all specimens.
Sclerosing mucoepidermoid thyroid carcinoma with eosinophilia. A distinctive low-grade malignancy arising from the metaplastic follicles of Hashimoto's thyroiditis.
Chan JK, Albores-Saavedra J, Battifora H, Carcangiu ML, Rosai J.
Department of Pathology, Yale University School of Medicine, New Haven, CT 06510
Am J Surg Pathol. 1991 May;15(5):438-48. Abstract quote
Eight cases of a distinctive low-grade carcinoma of the thyroid gland occurring in a background of Hashimoto's thyroiditis are reported. The patients were women presenting with a painless thyroid mass. Grossly, the tumors were white, homogeneous, firm, and usually ill defined.
Histologically, strands and small nests of squamoid tumor cells exhibiting mild to moderate nuclear pleomorphism, distinct nucleoli, and pale cytoplasm infiltrated an abundant, dense fibrohyaline stroma. Foci of definite squamous differentiation and small pools of mucin were often found within the tumor nests. The neoplastic cells were immunoreactive for cytokeratin, but not for thyroglobulin or calcitonin. The stroma and many of the tumor islands were infiltrated by eosinophils in all cases. Extrathyroidal extension occurred in five cases and lymph node metastases in one.
This tumor seems to arise from the benign squamous nests sometimes associated with mucin deposition found in Hashimoto's thyroiditis and thought to be the result of metaplastic changes of the follicular epithelium. It shares several morphologic features with cases previously reported as mucoepidermoid carcinoma of the thyroid, but it differs from them in other respects.
The differential diagnosis includes undifferentiated/squamous cell carcinoma, intrathyroidal thymic carcinoma, and direct extension or metastasis of carcinoma from other organs.
VARIANTS CLEAR CELLS Clear cells and thyroid transcription factor I reactivity in sclerosing mucoepidermoid carcinoma of the thyroid gland.
Albores-Saavedra J, Gu X, Luna MA.
Department of Pathology, Louisiana State University Health Sciences Center School of Medicine, Shreveport, LA 71130, USA.
Ann Diagn Pathol. 2003 Dec;7(6):348-53. Abstract quote
Clear cells have been described in mucoepidermoid carcinoma of the salivary glands, but to our knowledge these cells have not been recognized as a distinctive component of sclerosing mucoepidermoid carcinoma with eosinophilia of the thyroid gland.
We report four examples in which sclerosing mucoepidermoid carcinoma of the thyroid gland contained a minor component (10% to 30%) of clear cells. The four tumors occurred in women with Hashimoto's thyroiditis whose ages ranged from 38 to 52 years. All four patients presented with thyroid nodules, but two also had enlarged cervical lymph nodes. Although two tumors metastasized to multiple cervical lymph nodes and one recurred in the soft tissues of the neck, all four patients are disease-free 6 months to 6 years after surgical treatment. The locally aggressive behavior of the first three tumors was probably related to their size, rather than to the presence of clear cells.
Microscopically, these tumors showed the classical features of sclerosing mucoepidermoid carcinoma with eosinophilia, as well as nests of clear cells that appeared to be glycogen-rich squamous cells.
Although the four tumors were thyroglobulin negative, two were immunoreactive to thyroid transcription factor 1 (TTF-1), supporting the idea that they originated from squamous metaplasia of follicular epithelium rather than from solid cell nests of the ultimobranchial body.
CHARACTERIZATION SPECIAL STAINS IMMUNOPEROXIDASE p63
p63 expression in sclerosing mucoepidermoid carcinomas with eosinophilia arising in the thyroid.
Hunt JL, LiVolsi VA, Barnes EL.
Department of Pathology, University of Pittsburgh Medical Center, PA 15213, USA.
Mod Pathol. 2004 May;17(5):526-9. Abstract quote
Primary sclerosing mucoepidermoid carcinomas with eosinophilia (SMECE) of the thyroid gland are rare tumors that can present diagnostic difficulties to the pathologist due to the unusual histologic features.
Furthermore, the etiology of these tumors has been debated in the literature, with some authors believing that the tumors arise from remnants of the ultimobranchial body (UBB, solid cell nests) and others proposing that they arise from follicular epithelial cells. Because SMECE often occur in glands with chronic lymphocytic thyroiditis and UBB hyperplasia, and do not stain like follicular or parafollicular cells, it is likely that the tumors do arise from UBB/solid cell nests.
In this study, we provide additional evidence for this relationship, by demonstrating that SMECE stain strongly positive for p63, which is a new marker for UBB/solid cell nests.
DIFFERENTIAL DIAGNOSIS KEY DIFFERENTIATING FEATURES MUCOEPIDERMOID CARCINOMA, PRIMARY Primary mucoepidermoid carcinoma and sclerosing mucoepidermoid carcinoma with eosinophilia of the thyroid gland: a report of nine cases.
Baloch ZW, Solomon AC, LiVolsi VA.
Department of Pathology and Laboratory Medicine, University of Pennsylvania Medical Center, Philadelphia 19104, USA.
Mod Pathol. 2000 Jul;13(7):802-7. Abstract quote
Mucoepidermoid carcinoma is a rare primary thyroid tumor with indolent biologic potential. Two types of tumors have been described under this category: mucoepidermoid carcinoma (MEC) and sclerosing mucoepidermoid carcinoma with eosinophilia (SMECE).
The MEC shows both squamous and glandular differentiation in a background of a noninflamed gland, whereas SMECE is characterized by extensive sclerosis, squamous and glandular differentiation, a concomitant inflammatory infiltrate rich in eosinophils, and a background of lymphocytic thyroiditis.
We present nine cases of these entities: five MEC and four SMECE. All tumors occurred in women (age 27 to 73 years). Five tumors showed extrathyroidal invasion and multiple lymph node metastases. One case of MEC showed a concomitant tall cell variant of papillary carcinoma with vascular invasion, and two cases showed intimately associated areas of usual papillary carcinoma. One of the latter cases also showed areas of transformation to anaplastic carcinoma. In all cases of SMECE and in only one case of MEC, the uninvolved thyroid tissue showed lymphocytic thyroiditis. Follow-up information was available in four of the nine cases (3 months to 7 years). Two patients with SMECE are alive with no evidence of disease. One patient with MEC and tall cell variant of papillary carcinoma died of disease after 3 months, and the patient with anaplastic carcinoma died after 5 months with lung metastasis. Both MEC and SMECE were positive for cytokeratin and negative for calcitonin.
All cases of MEC were positive for thyroglobulin, whereas all cases of SMECE were negative. The immunohistochemical findings suggest that both MEC and SMECE have different histogenesis.
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