ThyroidCase 12.

Balázs Járay

• 74 year old male patient with a 13 mm large hypoechogenic, inhomogenous lesion in the left lobe of the thyroid gland. The nodule showed marked hypervascularity.

• US guided FNA was performed.

Cells in cohesive aggregates radially oriented around the central core

Cytoplasm was abundant, and the nucleocytoplasmic ratio was low.

Intranuclear cytoplasmic inclusions, nuclear grooves, and nuclear overlapping were very common

The combination of a bloody background, radially oriented cohesive cells, psammoma bodies, cells with abundant cytoplasm, nuclei with very frequent cytoplasmic inclusions and grooves, we suggested the presence of PTC or Medullary cancer.

Calcitonin immunostaining was negative

Serum calcitonin level was normal

Final opinion:

Probably papillary thyroid carcinoma

• Chromogranin, synaptophysin, calcitonin CK19 immunostainings were negative

• Dg.: Hyalinizing trabecular tumour

• Histopathology: prominent trabecular arrangement: trabeculae may be straight or curved, resulting in curious organoid formations

• In the cytoplasm of tumor cells due to accumulation of intermediate filaments in the extracellular space due to heavy deposition of hyalinized collagen fibers and basement membrane material

• Growth pattern may simulate that of paraganglioma and medullary carcinoma

• Distinct features: pseidoinclusions, nuclear grooves and psammoma bodies may suggest papillary carcinoma, particularly fine needle aspiration

• ‘Cytoplasmic yellow bodies’: round, pale yellow cytoplasmic inclusion bodies in a paranuclear location

• RET/PTC mutations

• Special Stains and Immunohistochemistry• Consistent positivity for thyroglobulin

• Focal and inconstant reactivity for neuroendocrine markers such as:

neuron-specific enolase (NSE)

neurotensin

• cytoplasmic (instead of nuclear) immunoreactivity with at least some of the monoclonal antibodies used to detect MIB-1

• Heavy deposition of type IV collagen:

around tumor cells (partially explaining ‘hyaline’ appearance)

surprisingly, in the nuclear pseudoinclusion

Differential Diagnosis

– Papillary Carcinoma

– Medullary Carcinoma