Page 562 - Concise Pathology for Exam Preparation ( PDFDrive )

20 Endocrinology 547

• Cells show finely dispersed chromatin, imparting an optically clear or empty appearance
to the nuclei (Orphan Annie or ground glass nuclei).
• Invaginations of the cytoplasm may in cross-sections give an appearance of eosinophilic
intranuclear inclusions or pseudoinclusions or intranuclear grooves.
• Concentrically calcified structures called psammoma bodies, usually located within
cores of papillae, are often seen.
• Lymphatic invasion is common; however, involvement of blood vessels is relatively
rare.
Note: Diagnosis of PTC is based on nuclear features irrespective of the presence or absence
of papillary architecture.
Variants
• Encapsulated variant: Well encapsulated, vascular or lymph node dissemination rare,
and excellent prognosis
• Follicular variant: Unencapsulated tumours with a follicular architecture, characteristic
nuclear features of PTC and psammoma bodies
• Tall cell variant: Neoplastic epithelium is tall columnar with intensely eosinophilic
cytoplasm. Large tumours, often present with vascular invasion and local and distant
metastases. Older individuals have a worse prognosis. Hürthle cell neoplasms are a close
differential.
• Diffuse sclerosing variant: Younger individuals including children are affected;
show diffuse fibrosis, abundant psammoma bodies and squamous morules
(metaplasia).
• Hyalinizing trabecular tumour: Organoid growth (resembles extra-adrenal paraganglioma),
both intra- and extracellular hyalinization are seen.
Prognosis
• Ten-year survival 98%
• Metastasis seen in 10–15% cases
Follicular Carcinoma
Clinical features
• Second most common thyroid carcinoma
• Peak incidence between 40 and 50 years; females more commonly affected than males
• Incidence higher in areas with iodine deficiency; indicating that follicular carcinoma
might arise from nodular goitre
• No definite evidence that follicular carcinoma arises from adenomas except for common
RAS mutations
• Presents as a slowly enlarging painless cold nodule
• Regional lymph nodes rarely involved; vascular invasion common with spread to bones,
lungs and liver
Gross morphology:
• Solitary nodule; may be well circumscribed or infiltrative
• Grey-tan-pink, translucent (due to large colloid-filled follicles)
• Degenerative changes, eg, central fibrosis and foci of calcification are common.
Microscopy:
• Most tumours show a follicular pattern; in some cases, follicular differentiation is less
apparent; trabecular pattern, sheets of polygonal to spindle-shaped cells and Hürthle
cells are more prominent.
• Anaplasia is variable (generally not marked).
• Blood vessels are preferentially invaded than lymphatics.
Types
1. Minimally invasive
2. Widely invasive (extensive invasion of adjacent thyroid parenchyma or extra-thyroidal
tissue)
Prognosis
• Most follicular carcinomas are treated with total thyroidectomy followed by
administration of radioactive iodine. Better differentiated lesions are treated with
thyroid hormones to suppress endogenous TSH (better-differentiated lesions are
stimulated by TSH).

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