Activating BRAF mutation in sclerosing mucoepidermoid carcinoma with eosinophilia of the thyroid gland: two case reports and review of the literature

Abstract

Background: Sclerosing mucoepidermoid carcinoma with eosinophilia is a rare form of thyroid carcinoma. The underlying molecular mechanisms of sclerosing mucoepidermoid carcinoma with eosinophilia tumorigenesis remain unknown.

Case presentation: We present two cases of sclerosing mucoepidermoid carcinoma with eosinophilia, both with a concurrent papillary thyroid carcinoma. Patient 1, a 70-year-old Caucasian woman, presented with sclerosing mucoepidermoid carcinoma with eosinophilia with distant renal metastasis and coexisting papillary thyroid carcinoma. Patient 2, a 74-year-old Caucasian woman with a remote history of thyroid cancer treated with thyroidectomy, presented with locoregionally invasive sclerosing mucoepidermoid carcinoma with eosinophilia and recurrent papillary thyroid carcinoma in the thyroid bed. BRAF mutation studies were performed on the sclerosing mucoepidermoid carcinoma with eosinophilia tumors. In both cases, sclerosing mucoepidermoid carcinoma with eosinophilia was positive for the BRAF V600E mutation by polymerase chain reaction. Patient 1 is the first reported case of sclerosing mucoepidermoid carcinoma with eosinophilia with renal metastasis, to the best of our knowledge.

Conclusions: Our findings suggest, for the first time, to our knowledge, involvement of the RAS-RAF-MEK-ERK signaling pathway in the pathogenesis of sclerosing mucoepidermoid carcinoma with eosinophilia. Thus, BRAF inhibitors may prove to be a useful targeted medical therapy in the treatment of a subset of patients with aggressive sclerosing mucoepidermoid carcinoma with eosinophilia tumors who exhibit BRAF activating mutation.

Keywords: BRAF; Renal metastases; Sclerosing mucoepidermoid carcinoma with eosinophilia; Thyroid cancer; V600E.

Fig. 1

Axial computed tomography of the abdomen of patient 1 at the level of kidneys showing right renal metastases of primary thyroid sclerosing mucoepidermoid carcinoma with eosinophilia (arrow)

Fig. 2

Pathology from right kidney biopsy of patient 1 shows sclerosing mucoepidermoid carcinoma with eosinophilia consistent with pathology from primary thyroid tumor. Histology shows (a) mucoid changes (hematoxylin and eosin (H&E) stain; original magnification, × 10), (b) epidermoid desmoplasia (hematoxylin and eosin (H&E) stain; original magnification, × 20), and (c) eosinophils present in inflamed stroma (hematoxylin and eosin (H&E) stain; original magnification, × 40)

Fig. 3

a Classic papillary thyroid carcinoma (PTC) on left upper corner and sclerosing mucoepidermoid carcinoma with eosinophilia (SMECE) on right lower corner (hematoxylin and eosin (H&E) stain; original magnification, × 2). b Nests of squamoid cells in a background of fibrous stroma and numerous eosinophils (hematoxylin and eosin (H&E) stain; original magnification, × 40). c Cytokeratin AE1/AE3 stain highlights classic PTC on left upper corner and infiltrating SMECE on right lower corner (IHC; original magnification, × 2). d Thyroglobulin stain is positive in classic PTC and negative in SMECE (IHC; original magnification, × 10)