Hepatic metastases from the spindle cell variant of medullary thyroid carcinoma - Report of a case with diagnosis by fine needle aspiration biospy

BACKGROUND: The liver is a common site of neuroendocrine tumors (NTs) metas tatic from primaries in the gastrointestinal tract, pancreas, biliary syste m and lungs. Medullary thyroid carcinoma (MTC) is also a potential source o f metastases of NTs. Their metastases to the liver are frequent and can app ear several years after the primitive tumor. Although a wide variety of cyt omorphologic features are normally exhibited by MTC in smears, a spindle-sh aped cell pattern can predominate, complicating the correct interpretation of a metastasis. CASE: A 63-year-old man presented with multiple liver nodules two years aft er a total thyroidectomy for MTC. Fine needle aspiration biopsy smears of t he liver revealed neoplastic cells occurring in loose groupings or lying si ngly, most of them with a spindle shape and elongated nucleus with the char acteristic "salt and pepper" chromatin pattern of a neuroendocrine tumor. C ytoplasmic dendritic processes and intranuclear inclusions were frequently seen. The cytomorphologic features of the tumor were essentially the same a s those of the primary MTC. Immunoreactivity for calcitonin confirmed the d iagnosis. CONCLUSION: In fine needle aspiration biopsy of liver masses, knowledge of the spindle pattern of the NT is important in order to achieve a correct di agnosis when metastases are the first manifestation of an occult primary tu mor. Among neuroendocrine tumors, MTC Must be included in the differential diagnosis.