Cribriform Morular Variant of Papillary Thyroid Carcinoma: Morphological Characteristics of an Unusual Tumor That Distinguish the Inherited and Sporadic Subtypes
Christina M Kovacs, Vania Nose. University of Miami, Miami, FL; Jackson Memorial Hospital, Miami, FL
Background: The cribriform morular variant of papillary thyroid carcinoma (CMv-PTC) is an extremely rare tumor classically known to be associated with familial adenomatous polyposis (FAP). The literature suggests that there is a rare, sporadic form as well. CMv-PTC occurs almost exclusively in females, is well differentiated and has a characteristic appearance on H&E. We reviewed the pathologic findings and associated clinical, laboratory and molecular findings of all cases from our files.
Design: We reviewed the pathologic and immunohistochemical findings of nine cases of CMv-PTC. Clinical histories were reviewed for the presence or family history of FAP, in addition to molecular results. We compared the pathologic findings between the FAP-associated tumors (7/9) and those classified as sporadic (2/9).
Results: All patients were female and ranged from 18 to 53 years of age. The FAP associated tumors were small (0.1 – 1.5 cm), multifocal (range 6 -13 nodules), bilateral and two cases showed lymph node metastases. Histologically, these tumors showed features of CMv-PTC with areas of cribriform, solid and morular growth and abundant fibrosis. The sporadic tumors were unifocal and larger (both 3.0 cm). One case was encapsulated and the other showed a metastatic focus in one lymph node. Histologically, these tumors also had areas of cribriform, solid and morular architecture, though these tumors had significantly less fibrosis than the FAP-associated tumors. The immunohistochemical profile was similar between the two groups, with both groups showing aberrant nuclear and cytoplasmic staining with beta-catenin. The tumors were also positive for galectin-3, CK19, p53 and cyclin D1. HBME1 was negative in the sporadic cases and weak or negative in the FAP-associated tumors. Both subtypes were associated with good prognosis and lacked local invasion.
Conclusions: CMv-PTC occurs sporadically and as an extraintestinal manifestation of FAP. Both groups show similar immunophenotype and architecture with cribriform, morular and solid areas; however, sporadic tumors are unifocal, larger and associated with less fibrosis histologically. It may be possible to differentiate sporadic cases of CMv-PTC from those that are FAP-associated based on size, focality, and amount of fibrosis.
Tuesday, March 20, 2012 1:00 PM
Poster Session IV # 32, Tuesday Afternoon