Case 5
Clinical features :
Female patient, 65 years old. Euthyroid large nodule.
Gross features :
Large, left , 7 cm nodule, solid, grayish, with foci of necrosis. Irregular thick
capsule.
| Microscopy : |
|
|
| The predominant pattern of growth is made of well-defined
nests (insulae) solid (fig A),
or cribriform with abortive follicles (fig B), centered by small lumina that contain colloid. |
|
 |
|
|
fig. A |
| Those nests are separated from each other by loose connective
tissue stroma. |
|
 |
|
|
fig. B |
| Foci of necrosis are frequent.(fig C). |
|
 |
|
|
fig. C |
The insulae are composed of small monotonous tumor cells with
round nuclei and scant cytoplasm (fig
D). Mitosis are always present but in variable number.
This tumor is aggressive with large capsular infiltration and blood vessel invasion. |
|
 |
|
|
fig. D |
Diagnosis :
Poorly differentiated carcinoma, insular type, intra-thyroid, p T3 stage.
Comments :
This tumor can be confused with :
- -medullary carcinoma and other neuroendocrine neoplasms metastatic to
thyroid (thymus, lung), because of its carcinoid-like insular configuration.
Immunohistochemical study demonstrate the follicular-cell appartenance of those tumors :
the cells are positive with Thyroglobulin and negative with neuro-endocrine markers as
well as Calcitonin.
- trabecular/solid variant of papillary carcinoma : this juvenile form
has a solid pattern but the cells retain the nuclear characteristics of papillary
carcinoma and there is no necrosis
- atypical follicular adenoma " fœtal type " in the
absence of obvious invasion, but those microfollicular lesion should be considered with
caution and studied carefully.
Poorly differentiated carcinoma, insular type, is viewed as a variant of follicular
carcinoma in the WHO Classification (1988). However, a large number of those tumor are
associated with papillary carcinoma.
Prognosis :insular carcinoma is an aggressive and often lethal tumor : metastases are
common both to regional lymp nodes and to distant sites (lung and bones).
However, the prognostical signification of a small focus of insular pattern in well
differentiated tumor is not clear. In such situation, the pathologist must estimate in
percentage the amount of insular pattern.
Other poorly differentiated tumors are composed of larger cells as well as oxyphilic or
clear cells.
References :
AKSLEN Li VOLSI
Poorly differentiated carcinoma - it is important
Am. J. Surg. Pathol. 2000 ; 24 : 310 - 11
CARCANGIU ML., ZAMPI G., ROSAI J.
Poorly differentiated ("insular") thyroid carcinoma.
Am. J. Surg. Pathol. - 1984 - vol. 8 - p. 655-668
DECAUSSIN M PEIX JL TOURNIAIRE J BERGER N
Cancers de la thyroïde d'évolution métastatique : fréquence d'un contingent insulaire
dans la tumeur primitive. A propos de 115 cas
Ann. Pathol 1999 ; 19 : S 53
|
