The diagnosis of thyroid carcinoma is based on specific cytomorphological characteristics. However, these characteristics can occur in other benign and malignant thyroid lesions. In such cases, immunohistochemistry seems to play an important role in order to facilitate the uncertain results and helps to avoid diagnostic pitfalls.
Papillary thyroid carcinoma (PTC) is the most common thyroid malignancy. The diagnosis of PTC is based on nuclear features, however identification of these features is inconsistent and controversial, and accordingly the microscopic distinction of PTC from other benign thyroid lesions may be difficult. In a few cases, the histopathology of papillary thyroid hyperplasia and PTC may be similar enough to cause a diagnostic dilemma.
The most common challenge in thyroid pathology is differentiating follicular variant papillary thyroid carcinoma from other follicular patterned nodules such as hyperplasyic nodule, follicular adenoma and follicular carcinoma. The distinction is critical for prognosis and management. The interobserver variability in this area is well recognized.
In an attempt to resolve these diagnostic difficulties, several immunostains have been proposed to aid in the diagnosis and differential diagnosis of thyroid carcinoma.
This work aims at evaluating the expression of HMWCK(34BE12) and CK19 antibodies in the thyroid neoplastic lesions, in an attempt to evaluate their possible diagnostic utility either singly or in combination in routine practice regarding the diagnosis and differentiation of thyroid carcinoma from their benign mimics especially when dealing with follicular patterned lesions .
This retrospective study was conducted on 70 selected cases of different surgically removed thyroid lesions which were received at Faculty of Medicine , Benha university and National cancer Institute , Cairo university during the period from January 2005 to December 2011.
All the 70selected cases were classified into 6 cases of hyperplastic nodules , 6 cases of follicular adenoma, 9 cases of atypical nodules with questionable nuclear features ,22 cases of papillary thyroid carcinoma,17 cases of follicular carcinoma, 5 cases of anaplastic carcinoma, 5 cases of medullary carcinoma,
Furtherly all the cases were subjected to the following:
Clinicopathological study: available clinicopathhological data were recorded including age and sex of the patients, multiplicity of the lesions and metastases
Immunohistochemical study: immunostaining with anti-HMWCK(34BE12) and CK19 antibodies was done using streptavidin-biotin immunoperoxidase technique
The following parameters were assessed:
- The pattern of HMWCK(34BE12) and CK19 immunoreactivity was considered positive when it is expressed in the cytoplasm with or without membraneous accentuation.
- Both HMWCK (34BE12) and CK19 expression were judged as negative if 50% of lesional cells were stained positive.
The studied 70 cases were classified into:
A)- Benign group (12 cases):
-Follicular adenoma: 6 cases - hyperplastic nodules: 6 cases .
B)- Borderline group (9 cases ):
- Atypical nodules: 9 cases
C)- malignant group (49 cases) :
Papillary thyroid carcinoma :
Classic PTC : 10 cases -
Follicular variant : 7 cases
Micropapillary variant : 5 cases
Follicular carcinoma : 17 cases
Anaplastic carcinoma : 5 cases
Medullary carcinoma : 5 cases
It was found that positive CK19 expression was recorded in 100% of studied 17 cases of follicular carcinoma and in 76.5% of PTC cases. CK19 has diagnostic value in differential diagnosis of follicular carcinoma from benign group. At the same time, 83.3% of benign group showed negative CK-19 expression. The result showed that diffuse HMWCK(34BE12) expression was highly significant correlated with PTC diagnosis , as it was expressed in 100% of studied PTC cases , in the same time , other studied cases either within malignant group or benign group showed negative HMWCK (34BE12) expression in . So HMWCK(34BE12) has a highly diagnostic value in detection of PTC and differential diagnosis from other mimics
. On the basis of the results of this study; that showed a complementary nature of HMWCK (34BE12) and CK19 utility; a protocol was suggested to identify various degree of risk potential for malignancy as follow:
a. Definite malignancy can be supposed if:
i. Both HMWCK (34BE12) and CK19 are diffusely expressed
PTC .
ii. HMWCK (34BE12)alone is diffusely expressed .PTC
iii. CK19 alone is diffusely expressed Follicular carcinoma
b. Borderline group can be suggested if:
HMWCK(34BE12) is diffusely or focally expressed and CK19 is negative atypical nodule (WDT-UMP).
c. Benign diagnosis can be considered if:
HMWCK(34BE12) and CK19 are negative Adenoma & hyperplastic nodule
Therefore, on the basis of the results of this study it is recommended that HMWCK (34BE12) is highly suggested for use in diagnosing and differentiating PTC variants from their benign mimics especially when dealing with patterned follicular lesions and papillary neoplastic lesions. CK19 is recorded diagnostic value in follicular carcinoma diagnosis and their differential diagnosis. Additional researches and follow up studies on large numbers of cases should be conducted to throw the light on the borderline category including well differentiated tumor of uncertain malignant potential ( WDT –UMP) & follicular tumor of uncertain malignant potential( FT-UMP), and to validate exactly the role of HMWCK (34BE12)and CK19 as diagnostic markers in routine work for such challenging cases.
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