6. Papillary carcinoma
“A malignant epithelial tumor showing evidence of follicular cell
differentiation and characterized by distinctive nuclear features”
-W.H.O.
7. Most common thyroid malignancy
Palpable nodule
Nodule in multinodular goitre (in iodine insufficient areas)
More common in females, rare before 15 years
Mean age at diagnosis approximately 40 years
Accounts for >90% of thyroid malignancies in children.
In 5–10% , history of neck irradiation
Increased incidence in Hashimoto's thyroiditis
Disease localized to:
thyroid gland in 67%
thyroid and lymph nodes in 13%
lymph nodes alone in 20%
Overall survival excellent
8. GROSS pathology
Size of the primary ranges from
microscopic to huge
Many thyroid cancers measuring
<1 cm in diameter are papillary
Most:
solid
whitish
firm
clearly invasive
<10% are surrounded by a
complete capsule
9. Histopathology
(PTC)
Numerous true papillae
Papillae are usually: complex,
branching, and randomly oriented, with
a central fibrovascular core and a single
or stratified lining of cuboidal cells
Stroma of the papillae:
edematous or hyaline
may contain lymphocytes, foamy
macrophages, hemosiderin, or -
exceptionally - adipose tissue
Follicles tend to be irregularly shaped,
tubular, and branching
Cells have characteristic nuclear
features
10. NUCLEAR FEATURES
(optically clear) nuclei:
often large with an overlapping
quality
nucleolus usually inconspicuous
and pushed against the nuclear
membrane, which appears
thickened
particularly prominent in tissue
fixed in high concentrations of
formalin
11. Nuclear
pseudoinclusions:
represent invaginations of the
cytoplasm
appear as sharply outlined
acidophilic formation
readily apparent in frozen section
specimens and aspirations
immunoreactivity for β-catenin and
sometimes type IV collagen
12. Nuclear grooves
Occur in oval or
spindle nuclei
Arranged along the
longest nuclear
axis
Represent
infoldings of a
redundant nuclear
membrane
Mitoses are scanty or
absent
intranuclear grooves (400×).
13. Psammoma bodies
Laminatedated basophilic
structures that:
stain for mucin, calcium, and iron
appear to arise from necrosis of
individual tumor cells, which occasionally
may be seen at their center
in approximately 50% of cases
may be located in:
the papillary stalk
fibrous stroma
between tumor cells in solid foci
14. Psammoma body formation in papillary
carcinoma beneath the capsule of a
if found in normal cervical lymph node, without identifiable
thyroid tissue or
lymph nodes from
the neck, a
papillary
carcinoma is likely
in the immediate
vicinity
15. OTHER CHANGES
LYMPHOCYTIC SCATTERED MULTINUCLEATED
INFILTRATION OF THE GIANT CELLS:
STROMA: -may be present
-25% of cases -probably a response to
MANY TUMORS ALSO leakage of colloid.
BLOOD VESSEL INVASION:
EXHIBIT:
-5% of cases
-a heavy infiltrate S-100
protein-positive
dendritic/Langerhans' cells
16. Metastasis
Papillary carcinoma invades the glandular lymphatics
Cervical lymph nodes metastases:
common (particularly in young patients)
may be the first manifestation
Blood-borne metastases:
less frequent than with other thyroid carcinomas
most common site is lung
also in bones, central nervous system, other organs
17. Metastasis
Regional lymph node metastases
are extremely common (≥50%)
This feature does not adversely
affect long-term prognosis.
Frequently the nodal metastasis
will involve one
node that may be cystic
19. Tumors with papillary and follicular structures
should be classified as papillary carcinoma
Thyroglobulin and TTF-1:
crucial markers when a papillary neoplasm is
in a lymph node or other extrathyroidal site
to establish whether the tumor is of thyroid
nature or not
most specific marker in existence (shared
with the pulmonary epithelium)
21. Found incidentally
1 cm or less
Papillary microcarcinoma
Common incidental finding (≥25%) in thyroids removed for other
reasons
More common in males
Most common form of papillary carcinoma
Stellate appearance
Nonencapsulated, white to tan nodule often located
subcapsularly.
Histologically, the tumors may be totally follicular or show
papillary areas as well
the lesions can infiltrate the surrounding thyroid
25. Encapsulated variant of PTC
presents grossly as an adenoma
comprises from 8% to 13% of papillary cancers
Microscopically, such lesions usually show total
encapsulation;
however, there are cytologic features of papillary
cancer, including nuclear changes and psammoma
bodies.
The prognosis is excellent.
26. Follicular variant of PTC
PTC composed of entirely or almost entirely of follicles.
Diagnosis is largely based on the nuclear features Supportive
features for the diagnosis are:
invasive growth pattern
psammoma bodies
strongly eosinophilic colloid with scalloped edges
abortive papillae
27. Follicular variant of papillary carcinoma.
Note the clear overlapping nuclei.
PIPELLE,
28. FVPTC
Solid Variant
Particularly common in children
Proliferation predominates over secretion
Characterized by solid nests of generally round
shape that can be viewed as filled-up follicles
Distinguish from poorly differentiated
carcinoma:
the nuclear features are those of papillary
carcinoma
behavior is that of papillary carcinoma (or a little
worse), but notably different from that of poorly
differentiated neoplasms
Solid variant of papillary carcinoma. The nests
are separated by fibrohyaline strands
29. Macrofollicular Variant
Rarest form of PTC
Opposite of the solid variant in that
secretory activity results in large
dilated follicles so it resembles a
hyperplastic nodule
Some follicles are lined by cells with
large clear nuclei with grooves and
pseudoinclusions
Low incidence of metastasis
Macrofollicular variant’ of papillary
carcinoma. This lesion simulates
nodular hyperplasia. The nuclear
features that allow the diagnosis
cannot be seen at this magnification.
30. Diffuse Sclerosis Variant
3% of all papillary carcinomas
affects children and young adults, may
present as bilateral goiter.
permeates the gland outlining the
intraglandular lymphatics.
Characterized by:
diffuse involvement of one or both
thyroid lobes without formation of
dominant mass
dense sclerosis
abundant psammoma bodies
extensive solid foci
squamous metaplasia
heavy lymphocytic infiltration
extensive lymph vessel permeation
Numerous psammoma bodies are found
31. Oncocytic variant
Nuclear features are those of papillary carcinoma
Cytoplasm is abundant and has a granular oxyphilic quality
Pattern of growth may be papillary or follicular
May be encapsulated or invasive, resulting in a number of
possible combinations:
oncocytic
encapsulated oncocytic
oncocytic follicular
encapsulated oncocytic follicular variants
important to recognize this variant because it may be
confusedwith a Hurthle cell neoplasm
32. Tall cell variant
important subtype because of its potentially aggressive clinical
course.
elderly patients, and often presents as a large tumor with
extrathyroidal extension and metastases.
33. composed predominantly of cells whose heights are at least twice times
their widths.
characterized by:
papillae lined by a single layer of ‘tall’ cells (the height being at least
twice the width)
an abundant acidophilic, quasi-oncocytic cytoplasm
These features should be present in at least 50% of the tumor
Growth pattern is usually highly papillary
Nuclei usually lack the optically clear appearance, grooves, and
pseudoinclusions of papillary carcinoma and its other variants
More aggressive behaviour
34. PTC, tall cell variant.The cells contain abundant cytoplasm
and are about three times as tall as they are wide.
H&E.)
35. Tall cell variant of papillary carcinoma. Note
the abundant granular acidophilic cytoplasm
with oncocyte-like features.
36. Columnar cell variant
In the columnar cell carcinoma: there is prominent
stratification
The cytoplasm is clear (sometimes with subnuclear
vacuolization)
Outcome is largely predicated by tumor stage
Encapsulated columnar cell carcinomas have a favorable
course
Occasionally tall and columnar cells coexist in papillary
carcinoma
These tumors have advanced local growth and
extrathyroidal extension and show aggressive clinical
behaviour
37. Columnar cell variant of papillary carcinoma. The
papillae are lined by a pseudostratified layer of spindle
tumor cells.
38. Cardinal molecular alteration is an alteration of RET,which:
is a proto-oncogene on chromosome 10q11.2
encodes a transmembrane receptor with tyrosine kinase activity
Alteration of RET
not a germline point mutation (as in familial medullary carcinoma)
39. PROGNOSIS
Age
Nearly all the deaths occur when the tumor manifests after the age of 40 years
Gender, Females usually have a better prognosis
Extrathyroidal extension ,Adversely affects prognosis
Microscopic variant
History of previous irradiation, Does not affect prognosis
Tumor size
Roughly an inverse correlation between tumor size and prognosis
Capsule and margins
Tumors that are encapsulated or have pushing margins have a better outcome
Multicentricity
If this is prominent there is a greater incidence of metastasis and a lower chance
of disease-free survival
Distant metastases
Lung metastases have an adverse influence on prognosis
This influence is even greater for distant metastases in other sites, such as the
skeletal system
40. Poorly differentiated, squamous, or anaplastic foci
These features have a markedly detrimental effect on prognosis
Present in <5% of cases
EMA and Leu-M1 positivity
Immunoreactivity for EMA and Leu-M1 may be associated with
a more aggressive clinical course
DNA ploidy
A good correlation has sometimes been shown between
aneuploidy and aggressive behavior, Rb protein
pRB expression level is a reliable predictor of recurrence
Circulating tumor cells
Presence of circulating tumor cells (as determined with an RT-
PCR assay for thyroglobulin mRNA) seems to be associated with
a higher likelihood of metastatic disease
41. Follicular carcinoma
“A malignant epithelial tumor showing evidence of
follicular cell differentiation and lacking the diagnostic
nuclear features of papillary carcinoma”
- W.H.O
42. Follicular carcinoma
Relatively rare
(10 to 15% of thyroid malignancies )
Predilection for females
Incidence higher in iodine deficient areas
Mean age at diagnosis approximately 50 years
Almost always:
solitary
not occult
Two types
minimally invasive and
widely invasive
45. Grossly encapsulated tumor
Often:
solid and fleshy cut surface.
Most of the tumor is bound
by a capsule (irregular
whitish band around the
lighter central nodule).
the capsule is breached
48. Widely invasive follicular
carcinoma
High-risk counterpart of the minimally invasive subtype
Widespread infiltration of blood vessels and/or adjacent thyroid
tissue
Often lacks encapsulation
Many are poorly differentiated carcinomas at the cytoarchitectural
level
49. Diagnosis of malignancy:
depends entirely on blood vessel or capsular invasion
blood vessel invasion is almost never evident grossly. The
vessels should:
be venous caliber
be in or immediately outside the capsule (rather than within the
tumor)
contain one or more clusters of tumor cells attached to the wall
and protruding into the lumen
interruption of the capsule must be full thickness to qualify
as capsular invasion
distinguish foci of capsular invasion:
from capsular rupture from fine needle aspiration, which results
in a fissure-like quality with foci of recent or old hemorrhage and
florid stromal reparative changes
50. Metastases
common with the widely invasive type
<5% of minimally invasive tumors with blood vessel invasion
<1% of tumors diagnosed as carcinoma only on the basis of
minimal capsular invasion
Usually blood-borne (particularly to lung and bones)
rather than regional nodes
Skeletal metastases:
usually multicentric
have a predilection for the shoulder girdle, sternum, skull, and
iliac bone6
sometimes pulsate because of their vascularity (a feature shared
with metastatic renal cell carcinoma)
51. TERMINOLOGY
Capsular invasion: tumor penetration through the
tumour capsule unassosiated with the site of
previous FNAC
Vascular Invasion: presence of intravascular tumour
cells either covered by endothelium or associated
with thrombus
INVOLVED VESSELS MUST BE WITHIN OR BEYOND
CAPSULE
FOCI OF VASCULAR INVASION SHOULD BE
DISTINGUISHED FROM SUBENDOTHELIAL
COLLECTION Of tumor cells
54. Poorly differentiated carcinoma
Thyroid tumor that is, in differentiation and
behavior, intermediate between well-
differentiated (papillary and follicular
carcinoma) and anaplastic thyroid carcinomas.
55. Occurs in an older group than well-
differentiated tumors
Can occur in adolescents.
More common in some parts of Europe and
South America than in the United States
Behavior is generally aggressive
High incidence of nodal and blood-borne
metastases
60. Special Stains and
Immunohistochemistry
Thyroglobulin 60%
TTF-1: 40%
Not reactive for:
calcitonin
Usually:
focal reactivity for neuroendocrine markers
concentrate radioiodine (unlike undifferentiated carcinoma)
bcl-2
in over 80% of cases (rare in undifferentiated carcinoma)
p53
may be expressed
restricted to foci of infiltrative growth
61. Undifferentiated(anaplastic) thyroid
carcinoma
UTC are malignant tumours that histologically
appear wholely or partially composed of
undifferentiated cells that exhibit
immunohistochemical or ultrastructural
features indicative of epithelial differentiation
62. Usually elderly
5% of thyroid malignancies
Presentation:
rapidly growing mass
hoarseness
dysphagia
dyspnea
usually extrathyroidal extension
Rapid evolution:
massive growth in neck
infiltration of ribbon muscles, esophagus, trachea, skin, and contiguous
bones
commonly nodal and distant metastases
cause of death usually involvement of vital structures in the neck
extremely poor prognosis, with many patients surviving less than
6 months following diagnosis
63. Pathogenesis
Usually a result of
anaplastic
transformation of a
pre-existing well-
differentiated tumor
(or a metastatic
focus):
commonly papillary
carcinoma
Anaplastic thyroid carcinoma
showing residual papillary
carcinoma.
64. Gross anaplastic thyroid carcinoma showing a
large yellow, tan, white mass with areas of
hemorrhage.
66. Sarcomatoid: spindle cell and giant cell:
Composed of two patterns, often seen together
may exhibit:
a fascicular or storiform growth pattern
heavy neutrophilic infiltration
prominent vascularization
cartilaginous/osseous metaplasia
May be osteoclast-like multinucleated giant cells:
giving an appearance reminiscent of giant cell
tumor of bone or soft tissues
69. Special Stains and
Immunohistochemistry
Keratin 50-100%
CEA 50%
Throglobulin 5%
Vimentin: (consistently present in the spindle
cell component)
TTF-1 (generally negative)
70. Medullary carcinoma
Thyroid malignancy with C (parafollicular) cell differentiation.
5% of thyroid neoplasms
secrete calcitonin,
elaborate other polypeptide hormones, such as serotonin, ACTH,
and vasoactive intestinal peptide (VIP).
Two forms:
sporadic (approximately 80% of cases)
familial
The remainder 20% occurs in the setting of MEN syndrome 2A or
2B
Cases associated with MEN types 2A or 2B occur in younger
patients, and may even arise during the first decade of life.
sporadic as well as familial medullary carcinomas are lesions of
adulthood, with a peak incidence in the 40s and 50s.
71. Sporadic medullary carcinoma
Occurs in adults (mean age 45 years)
Almost always solitary
Presents as a thyroid mass that is cold on
thyroid scan
Sometimes accompanied by intractable
diarrhea or Cushing's syndrome
72. Familial medullary carcinoma
Autosomal dominant inheritance with virtually
complete penetrance.
Becomes clinically apparent at mean age 35
years
Most cases in children are familial medullary
carcinoma
Often multiple and bilateral
73. Typically:
solid
firm
nonencapsulated
relatively well
circumscribed
in the midportion or upper
half of the gland,
corresponding to a greater Unencapsulated quality, solid
concentration of C cells in appearance, and yellowish tan
this region color
74. Histopathology
Classically:
solid proliferation of
round to polygonal cells
with:
granular amphophilic
cytoplasm
medium-sized nuclei
highly vascular stroma
hyalinized collagen
amyloid
Low-power microscopic view
coarse calcification showing solid pattern of
growth and deposition of
amyloid.
75. Pattern of growth
can be:
carcinoid-like,
paraganglioma-
like
trabecular
glandular
(tubular and
follicular)
pseudopapillary
pseudopapillary pattern of
growth resulting from lack of
cohesiveness of tumor cells.
76. Special Stains and
Immunohistochemistry
Calcitonin+ 95 %
CEA++100%
Chromogranin+1
00
Keratin AE
1/3+100
TTF-1+90
Thyroglobulin
NSE
Synaptophysin Medullary carcinoma showing
immunocytochemical positivity for
calcitonin and congo red
77. Metastases
Cervical and mediastinal lymph nodes
Distant organs, particularly lung, liver, and skeletal
system
More common with sporadic and multiple endocrine
neoplasia (MEN)-IIB than MEN-IIA
May be the first manifestation and a source of confusion
78. Follicular adenoma
Benign encapsulated thyroid tumor that shows
evidence of follicular cell differentiation.
Most common thyroid neoplasm
Usually occurs in euthyroid adult
Thyroid lump
Elevated thyroglobulin levels common but clinical
hyperthyroidism (toxic adenomas) uncommon
Autonomously functioning tumors may be more
common in regions with iodine deficiency
79. Gross Pathology
Characteristically:
solitary
secondary degenerative changes, especially for larger tumors
such as
hemorrhage
edema
fibrosis
calcification
bone formation
cystic degeneration
surrounded by a generally thin capsule that is grossly and
microscopically complete
Architectural and cytologic features differ from those
of surrounding gland, which usually shows signs of
compression
81. Histopathology
A variety of patterns,
singly or in combination:
normofollicular (simple)
macrofollicular (colloid)
microfollicular (fetal;)
trabecular/solid
(embryonal)
Mitoses:
rare or absent
not necessarily indicators
of malignancy Microfollicular pattern of
growth in a follicular adenoma
83. Special Stains and Immunohistochemistry
Thyroglobulin+100 %
TTF+100 %
Reactivity for:
low-molecular-weight keratin and thyroglobulin in the cytoplasm
laminin and other basement membrane components around the
follicles
DNA aneuploidy:
found in about one-quarter of follicular adenomas
slightly more common in cellular types
not an indicator of clinical malignancy or increased risk of tumor
recurrence
84. Several variants
Hürthle cell adenoma
hyalinizing trabecular adenoma
Atypical adenoma:
pronounced cellular proliferation
less regular cytoarchitectural patterns
no capsular or blood vessel invasion
Adenoma with bizarre nuclei:
huge hyperchromatic nuclei, usually in clusters
no features of malignancy
Rare types of follicular adenoma:
clear cell changes (including signet ring, mucin-producing, and lipid-rich types)
adipose metaplasia of the stroma (adenolipoma)
cartilaginous metaplasia (adenochondroma)
massive deposition of cytoplasmic black pigment following minocycline therapy
(black adenoma)
86. Hürthle Cell Tumors
Follicular neoplasms composed of oncocytes
which are characterized by deeply eosinophilic
cytoplasm.
87. Usually adult
Predominance of females
Decrease or loss of bcl-2 expression suggests
that this is an early event
88. Histopathology
Cytoplasmic granularity:
due to accumulation of mitochondria
ultrastructurally many mitochondria show morphologic abnormalities
deeply eosinophilic quality in H&E-stained sections
follicular (most common)
trabecular/solid
papillary
May be:
large follicles separated by long and thin fibrovascular septa inspissated
intraluminal colloid with concentric laminations (an appearance similar
to psammoma bodies associated with papillary carcinoma, from which
they are distinguished by location)
Nuclei may show:
pleomorphism
prominent nucleoli
isolated bizarre forms
89. Hurthle Cell Carcinomas
Hürthle Cell Carcinomas
Predominantly or exclusively solid/trabecular
growth pattern
Highly invasive
Metastases:
mainly to lungs and bone
less commonly cervical nodes
90. Gross Pathology
Characteristically:
solid
tan
well vascularized
Usually well
encapsulated throughout
Invasive tumors tend to
grow into the
parenchyma in a
multinodular fashion Gross appearance of Hürthle
(can be underinterpreted cell carcinoma. The cut
as nodular hyperplasia) surface shows a tan color and
a necrotic hemorrhagic center
91. Hurthle cell carcinoma
Older age group
Less female predominance
Larger
Tends to have a
solid/trabecular rather than
a follicular growth pattern
Cells:
often smaller
higher nucleocytoplasmic
ratio
Proliferative activity is
higher, but the difference is
not sufficient for diagnostic
or prognostic purposes/
Hürthle cell carcinoma with a
predominantly solid pattern of growth
93. Special Stains and
Immunohistochemistry
CK 7+ 66%
TTF+ 33%
Thyroglobulin: 100%( Establishes thyroid origin)
Reactivity for:
thyroglobulin (less reactive than nononcocytic follicular cells)
keratin (CK14 is emerging as a selective marker for oncocytes)
CEA
S-100 protein
surprisingly, HMB-45
95. Hyalinizing trabecular tumour
HTT is a rare tumour of follicular cell origin with a
trabecular pattern of growth and marked intra-
trabecular hyalinization
Female predilection
Mean age 47 years
Solitary nodule
96. Suggestion that it may be a morphologic variant of papillary
carcinoma
features traditionally associated with papillary carcinoma,
such as nuclear grooves and pseudoinclusions and
psammoma bodies
expression of similar types of stratified epithelial-type
keratins
occasional cases contain foci of typical papillary
carcinoma
occasional cervical lymph node metastases of papillary
carcinoma have an HTA-like pattern
detection of RET/PTC mutations with a frequency similar
to or higher than that in papillary carcinoma
97. Histopathology
A peculiar adenoma exhibiting:
prominent trabecular
arrangement:
trabeculae may be straight or
curved, resulting in in the
cytoplasm of tumor cells due to
accumulation of intermediate
filaments
Growth pattern may simulate
that of paraganglioma and
medullary carcinoma
Distinct features:
nuclear grooves and
psammoma bodies:
may suggest papillary carcinoma,
particularly fine
Hyalinizing trabecular adenoma. A wide trabecula
is seen in the center of the picture, with the tumor
cells arranged perpendicularly to the longest axis.
99. Special stains and
immunohistochemistry
Consistent positivity for thyroglobulin
Distinctive cell membrane staining with MIB-1
Focal and inconstant reactivity for neuroendocrine markers such
as:
neuron-specific enolase (NSE)
neurotensin
Heavy deposition of type IV collagen:
around tumor cells (partially explaining ‘hyaline’ appearance)
101. TERATOMA.
neonates or infants under the age of 1 year as
huge midline neck masses.
Approximately 35% of women who deliver
babies with teratomas experience
polyhydramnios in pregnancy.
predominantly or partially cystic.
contained elements of all three germ layers and
have been benign.
Teratomas of the thyroid in adults differ from
those in newborns because they are more
frequently malignant
103. Malignant Lymphoma
involve the thyroid as part of systemic lymphoma
(secondary lymphoma) or may arise primarily in the
thyroid
Approximately 20% of patients dying of generalized
malignant lymphoma will show thyroid involvement
Thyroid replacement is rarely extensive enough to
produce clinical hypothyroidism
104. 1% to 3.5% thyroid cancers are malignant lymphomas.
Primary malignant lymphoma of the thyroid usually
arises in an immunologically abnormal gland, usually
one affected by chronic lymphocytic thyroiditis
Clinically, thyroid lymphoma affects women more
frequently than men (ratio of 2.5 to 8.4:1).
Most patients are older (age 50 to 80 years).
Grossly, appear as large fleshy tan or gray masses often
extending outside the thyroid capsule.
The most common histologic subtype is large-cell
diffuse lymphoma
Most thyroid lymphomas are of B-cell lineage
106. METASTATIC TUMORS TO THE
THYROID.
Metastases may reach the thyroid by direct extension
retrograde lymphatic spread, or
hematogenously.
Carcinomas of the larynx, pharynx, trachea, and esophagus may
invade the thyroid directly..
Hematogenous metastases to the thyroid vary according to tumor
type
A metastasis should always be considered when the histology is
unusual for a thyroid primary.
In surgical series, carcinomas of the kidney and colon and
melanoma are most commonly found to metastasize to thyroid
Grossly, such lesions are often solitary, circumscribed masses;.
Hinweis der Redaktion
Complex branching papillae only , don’t tell anything more Papillary architecture may be minor or absent
strongly suggest a diagnosis of papillary carcinoma rare in other thyroid lesions seen in paraffin and frozen sections, cytology preparations
Hence, attempts at staging papillary carcinoma may have minimal clinical significance.
It is important to recognize
Note the clear overlapping nuclei.
The nuclear features that allow the diagnosis cannot be seen at this magnification.
Diffuse sclerosis variant showing solid tumor nests and numerous psammoma bodies. Notice the lymphocytic infiltrates around the tumor foci
reminiscent of early secretory endometrium)
Dietary iodine supplementation has been assosioated with an increase frequency of papillary carcinoma and a decrease in relative frequency of follicular carcinoma. The frequency of follicular carcinoma has decreased recently due to exclusion from this categoryof follicular variant of otc
after violating a narrow segment of capsule, it is common for the tumor to expand in a mushroom-like fashion in the adjacent area
Low-power view of poorly differentiated thyroid carcinoma showing a well-developed insular pattern.
Sometimes co-exist
similar to normal C cells, secrete calcitonin the measurement of which plays an important role in the diagnosis and postoperative follow-up of patients This tumor is of great diagnostic importance because of its aggressiveness, its close association with multiple endocrine neoplasia (MEN) syndromes (MEN2A and MEN2B), and a relationship to a C-cell hyperplasia as the probable precursor lesion
Encapsulated lesions
Low-power view of follicular adenoma with bizarre nuclei. This feature is not a sign of malignancy and is analogous to that seen in many other endocrine tumors
An immunologically abnormal tissue produces the background for lymphoma development