Parathyroid Carcinoma  

Case 1 (22.7) Sex unknown, age mid 70’s, hypercalcaemia, 4cm nodule thought to be thyroid, for frozen section. A Parathyroid Carcinoma  showing features of malignancy with vascular invasion and capsular infiltration. Parathyroid carcinomas often have have a thick fibrous capsule with dense fibrous septa extending into and dividing the gland with growth in diffuse sheets, although areas of trabecular growth, spindle cells, palisading, or rosette-like growth may also be seen. Mitoses may be present but are not specific to carcinoma, although frequent mitoses (>1 per 10 hpf) should prompt a careful search for other malignant features and abnormal mitotic figures are more suggestive of malignancy. The most specific features of malignancy and some which are seen in this case are vascular invasion, perineural invasion, or direct extension into adjacent soft tissues. The major diagnostic problem is confusion between carcinoma and degenerative changes in a hyperplastic or adenomatous parathyroid gland with degeneration causing fibrosis and pseudoinvasion of the capsule.