A. WELL DIFFERENTIATED HURTHLE CELL CARCINOMA (8.5 cm., 125
grams) WITH ANGIOLYMPHATIC INVASION, CAPSULAR INVASION AND
FOCAL AREAS OF DEGENERATION.
B. ALL MARGINS OF RESECTION FREE OF TUMOR.
C. STAGE: T3,Nx,Mx.
Approximately five percent of all thyroid tumors are Hurthle cell tumors, and approximately five percent of all thyroid malignancies are Hurthle cell carcinomas. While there has been some controversy over the years regarding the prognosis and treatment of these lesions, many authors currently feel that Hurthle cell neoplasms are a variant of follicular neoplasms and ought to be diagnosed and treated similarly. In other words, those histologic features that define a malignant follicular lesion are the same that define a malignant Hurtle cell neoplasm. Factors that appear to have an impact on behavior include size (generally, tumors less than 1 cm. are never malignant), growth pattern (predominantly follicular tumors being benign, while solid tumors may not be), and ploidy (aneuploid tumors have been shown to behave more aggressively). The most important criteria for malignancy is the presence of capsular and/or angiolymphatic invasion. Nuclear atypia, even when it is severe, is considered to be a rather weak predictor of behavior, although mitotic activity is probably significant.
These tumors are characteristically brown, which can be useful when characterizing them grossly. Brown coloration is actually a feature of all oncocytic tumors regardless of organ of origin (eg., renal oncocytoma). The characteristic cytology that makes this particular case a Hurthle cell tumor is the preponderance of cells with eosinphilic, granular cytoplasm and low nuclear to cytoplasmic ratios. Ultrastructurally, oncocytes (Hurthle cells or Askanazy's cells) are packed with mitochondria.
ML Carcangiu, et al., Follicular Hurthle cell tumors of the thyroid gland, Cancer, 68:1944-1953, 1991
G Tallini, et al., Oncocytic neoplasms of the thyroid gland, Acta Pathol Jpn, 42:305-315, 1992
C Schark, et al., The value of measurement of RAS oncogenes and nuclear DNA analysis in the diagnosis of Hurthle cell tumors of the thyroid, World Journal of Surgery, 16:745-752, 1992
Contributed by Eric Schubert, MD