Medullary Thyroid Cancer

Abstract

In the 1950s the physicians of the Cleveland Clinic defined medullary carcinoma of the thyroid as a clinicopathologic entity (1,2). During the same decade a few were recognized independently as unusual tumors different from the majority of thyroid neoplasms (3). Subsequently, a thorough search of the literature revealed several other probable medullary carcinomas (4). The neoplasm consists of solid masses of rounded, polygonal, and/or spindled neoplastic cells of various sizes (Fig. 1), often mixed with amyloid, nearly always in the lateral lobes (5),rarely in the isthmus (4). Insular (micronodular, nesting) and trabecular (cordlike, ribbonlike) patterns are common Less obvious in many tumors are arrangements described as rosettes, pseudorosettes, and glandular, tubular, and follicular structures (4). Many medullary carcinomas contain microacini (6). Other characteristics include pseudopapillary and papillary patterns, solid “small cell,” “oat-cell,” and “neuroblastomalike” features (7), and more pleomorphic anaplastic patterns. “Plasmacytoid” cells (8), binucleated cells (4,7), and cells with very large nuclei, even giant nuclei (4) have been noted. Multinucleated neoplastic cells occur (4). Similarities to Askanazy/Hurthle cells have been illustrated or reported (9),as have squamous cell characteristics (10,11) and clear cells. Some tumors produce mucus, and rarely a few form melanin granules. Deposits of amyloid may be accompanies by giant cells of the foreign body type (2,4). A minority lack amyloid (4). Some are well-encapsulated (9). Within the carcinomas there may be focal necrosis (7,9), cystic change (7), irregular calcification, and psammoma bodies (4,9). The pathologist should search for necrosis, because its presence may be an indicator of a worse prognosis (12).