Histopathologic and clinical features of medullary microcarcinoma and C-cell hyperplasia in prophylactic thyroidectomies for medullary carcinoma: a study of 42 cases.
BACKGROUND
Prophylactic thyroidectomies are increasingly performed on patients at risk for developing medullary thyroid carcinoma (MTC); consequently, pathologists are more commonly encountering these specimens in routine practice.


OBJECTIVE
To describe the detailed clinicopathologic features of prophylactic thyroidectomies for medullary carcinoma.


METHODS
We present a retrospective series of 42 prophylactic thyroidectomies for MTC performed for one or more of the following: family history of multiple endocrine neoplasia (MEN) or MTC, elevated serum calcitonin level, or detection of a RET proto-oncogene mutation.


RESULTS
Patients included 22 men and 20 women (mean age, 26.2 years). Among those with known RET proto-oncogene mutations, affected sites included exons 10, 11, 14, and 16. In 93% (n = 39) of cases, either C-cell hyperplasia (n = 36), medullary microcarcinoma (MMC; n = 29), or medullary macrocarcinoma (n = 1) was found. C-cell hyperplasia was often multifocal (n = 30) and bilateral (n = 23) and included both nonnodular and nodular patterns. A total of 94% of C-cell hyperplasia cases and all MMC cases were microscopically detectable using hematoxylin-eosin stains. The MMCs were characterized by a complex microarchitectural pattern with a desmoplastic stromal response (n = 29) and focal amyloid deposition (n = 12). Most MMCs exhibited a solid pattern (n = 24) of round, polygonal, spindled, or plasmacytoid-shaped cells. Only 1 case of MMC showed evidence of metastatic disease to a pretracheal lymph node.


CONCLUSIONS
Based upon our clinicopathologic findings and review of the literature, we conclude that thyroidectomies in at-risk patients are very frequently associated with C-cell hyperplasia and/or MMC; however, the clinical prognosis for these patients is very good.
Etit
Demet
D
Department of Pathology, Massachusetts General Hospital, 55 Fruit St, Boston, MA 02115, USA.
Faquin
William C
WC
Gaz
Randall
R
Randolph
Gregory
G
DeLellis
Ronald A
RA
Pilch
Ben Z
BZ
D000293:Adolescent; D000328:Adult; D000368:Aged; D002116:Calcitonin / Q000097:blood; D018276:Carcinoma, Medullary / Q000473:pathology* / Q000517:prevention & control* / Q000601:surgery; D002648:Child; D002675:Child, Preschool; D005260:Female; D006801:Humans; D006965:Hyperplasia / Q000473:pathology; D008198:Lymph Nodes / Q000473:pathology; D008297:Male; D008875:Middle Aged; D009154:Mutation / Q000235:genetics; D010280:Parathyroid Glands / Q000473:pathology; D000090063:Proto-Oncogene Mas; D051096:Proto-Oncogene Proteins c-ret / Q000235:genetics; D012189:Retrospective Studies; D013961:Thyroid Gland / Q000473:pathology* / Q000601:surgery; D013964:Thyroid Neoplasms / Q000473:pathology* / Q000517:prevention & control* / Q000601:surgery; D013965:Thyroidectomy
C000715470:MAS1 protein, human; D000090063:Proto-Oncogene Mas; D002116:Calcitonin; D051096:Proto-Oncogene Proteins c-ret