Y. Morikawa et al., CYSTIC SQUAMOUS-CELL CARCINOMA OF THE THYROID - A POSSIBLE NEW SUBGROUP OF INTRATHYROIDAL EPITHELIAL THYMOMA, Endocrine pathology, 6(1), 1995, pp. 77-81
In the thyroid gland, both squamous cell carcinoma and intrathyroidal
epithelial thymoma are rare tumors with squamous features, but their p
rognoses differ; the former is usually fatal, and the latter is favora
ble. We describe a 38-yr-old female patient with a cystic tumor diagno
sed cytologically as squamous cell carcinoma, who was treated with sub
total thyroidectomy. The tumor was located intrathyroidally in the mid
dle third of the left lobe, and no invasion to the surrounding tissues
was found. Histologic examination disclosed a cyst lined by epithelia
l cells with squamous cell differentiation. The tumor cells had ill-de
fined cell borders and large nuclei with prominent nucleoli. Invasion
of the tumor capsule, a few mitoses, and infiltration of lymphocytes i
n the tumor periphery were noted, but neither necrosis nor metastasis
to lymph nodes was observed. The patient has been free from recurrence
for 3 yr after thyroid lobectomy. We propose that this type of cystic
intrathyroidal squamous cell carcinoma may represent a cystic variant
of intrathyroidal epithelial thymoma.