The correct diagnosis is: Medullary thyroid carcinoma

• This is a highly cellular specimen containing a mainly dispersed population of pleomorphic cells. The nuclei are round to oval and occasionally spindle-shaped, with granular salt and pepper chromatin best seen in the Papanicolaou stained material.
• In the MGG stained material red neuroendocrine cytoplasmic granules are identified, as well as occasional intranuclear inclusions. Dark blue amorphous material is most likely amyloid.
• These cytologic features are consistent with a medullary carcinoma of the thyroid.

• The biopsy reveals solid sheets and nests of large, polygonal malignant cells with amyloid deposits within a highly vascularised stroma
• Medullary carcinoma is a neuroendocrine type malignant tumour comprising approximately 5-10% of thyroid carcinomas.  Thought to arise from parafollicular C cells, tumour cells produce calcitonin which may be demonstrated by immunocytochemistry.  Elevated serum levels of calcitonin in conjunction with a thyroid nodule are virtually pathognomonic of medullary carcinoma.  Approximately 20% of cases are familial.  They tend to present at a younger age, may be bilateral and may occur as part of multiple endocrine neoplasia (MEN) syndrome.  However, the majority of cases are sporadic with a mean age range of 30-50 years and a slight female predominance.
• On tissue sections, tumour cells are usually polygonal but may be spindled or small and round in a carcinoid-like pattern.  Giant cells, clear cell, melanotic, mucinous and oncocytic forms have also been identified.
• Amyloid is a characteristic component of medullary carcinoma but the amount of amyloid within the tumour is variable.  On cytology, material stains purplish blue on Giemsa stains and pale green-blue on Papanicolaou stain.  Tumour cells are often very closely associated with amyloid, a feature that may help distinguish it from colloid.
• Intranuclear inclusions seen in up to 50% of medullary carcinomas may be a pitfall, suggesting papillary carcinoma.  Identifying red neuroendocrine cytoplasmic granules on air-dried Giemsa stained material and the coarser granular chromatin will help with this differential diagnosis.
• The aspirate usually lacks the microfollicular pattern typical of a follicular neoplasm, which also tends to demonstrate more uniform, round nuclei than that of medullary carcinoma.  The characteristic salt and pepper chromatin pattern also supports the diagnosis of a neuroendocrine carcinoma.
• Markedly pleomorphic, bizarre tumour cells often present in anaplastic carcinomas are rarely seen.
• The cytologic diagnosis of medullary carcinoma is best supported by immunocytochemical stains for calcitonin and other neuroendocrine markers, as well as serum analysis for calcitonin.

BACK TO IMAGES

HISTOLOGY

REFERENCES:

Geisinger KR, Stanley MW, Raab SS, Silverman JF, Abati A. Modern Cytopathology. Elsevier Churchill Livingstone; 2004, pp759-764.

McKee GT. Cytopathology. Mosby-Wolfe Times Mirror International Publishers Limited; 1997, pp104-107.

Demay, Richard M. The Art & Science of Cytopathology­: Chicago: ASCP Press, 1996. pp735-737

The correct diagnosis is: Medullary thyroid carcinoma

• This is a highly cellular specimen containing a mainly dispersed population of pleomorphic cells. The nuclei are round to oval and occasionally spindle-shaped, with granular salt and pepper chromatin best seen in the Papanicolaou stained material.
• In the MGG stained material red neuroendocrine cytoplasmic granules are identified, as well as occasional intranuclear inclusions. Dark blue amorphous material is most likely amyloid.
• These cytologic features are consistent with a medullary carcinoma of the thyroid.

• The biopsy reveals solid sheets and nests of large, polygonal malignant cells with amyloid deposits within a highly vascularised stroma
• Medullary carcinoma is a neuroendocrine type malignant tumour comprising approximately 5-10% of thyroid carcinomas.  Thought to arise from parafollicular C cells, tumour cells produce calcitonin which may be demonstrated by immunocytochemistry.  Elevated serum levels of calcitonin in conjunction with a thyroid nodule are virtually pathognomonic of medullary carcinoma.  Approximately 20% of cases are familial.  They tend to present at a younger age, may be bilateral and may occur as part of multiple endocrine neoplasia (MEN) syndrome.  However, the majority of cases are sporadic with a mean age range of 30-50 years and a slight female predominance.
• On tissue sections, tumour cells are usually polygonal but may be spindled or small and round in a carcinoid-like pattern.  Giant cells, clear cell, melanotic, mucinous and oncocytic forms have also been identified.
• Amyloid is a characteristic component of medullary carcinoma but the amount of amyloid within the tumour is variable.  On cytology, material stains purplish blue on Giemsa stains and pale green-blue on Papanicolaou stain.  Tumour cells are often very closely associated with amyloid, a feature that may help distinguish it from colloid.
• Intranuclear inclusions seen in up to 50% of medullary carcinomas may be a pitfall, suggesting papillary carcinoma.  Identifying red neuroendocrine cytoplasmic granules on air-dried Giemsa stained material and the coarser granular chromatin will help with this differential diagnosis.
• The aspirate usually lacks the microfollicular pattern typical of a follicular neoplasm, which also tends to demonstrate more uniform, round nuclei than that of medullary carcinoma.  The characteristic salt and pepper chromatin pattern also supports the diagnosis of a neuroendocrine carcinoma.
• Markedly pleomorphic, bizarre tumour cells often present in anaplastic carcinomas are rarely seen.
• The cytologic diagnosis of medullary carcinoma is best supported by immunocytochemical stains for calcitonin and other neuroendocrine markers, as well as serum analysis for calcitonin.

BACK TO IMAGES

HISTOLOGY

REFERENCES:

Geisinger KR, Stanley MW, Raab SS, Silverman JF, Abati A. Modern Cytopathology. Elsevier Churchill Livingstone; 2004, pp759-764.

McKee GT. Cytopathology. Mosby-Wolfe Times Mirror International Publishers Limited; 1997, pp104-107.

Demay, Richard M. The Art & Science of Cytopathology­: Chicago: ASCP Press, 1996. pp735-737