|Year : 2014 | Volume
| Issue : 1 | Page : 51-53
Papillary microtumor of thyroid: Benign or aggressive?
Akshatha S Kamath, HK Manjunatha, AS Ramaswamy, Vaibhav J Nayak
Department of Pathology, Peoples Education Society Institute of Medical Sciences And Research, Kuppam, Chittor, Andhra Pradesh, India
|Date of Web Publication||10-Mar-2014|
Akshatha S Kamath
Vignesh, 12th Cross, 2nd Main, T P Kailasam Road, Sapthagiri Extension, Tumkur-572 102, Karnataka
Source of Support: None, Conflict of Interest: None
Papillary carcinoma of thyroid is the most common type of thyroid malignancy. There are numerous histopathologic variants of papillary carcinoma of thyroid. Each variant shows a combination of specific growth patterns, cell types, and stromal changes. Metastases to cervical lymph nodes are very common. Papillary microtumor (PMiT) is an uncommon variant of papillary carcinoma of thyroid. It is usually an incidental finding at autopsies or in thyroidectomy or lobectomy specimens of benign disease. We report two cases of PMiT s with two different behaviors. The first case stresses the importance of extensive sampling of thyroidectomies for benign disease and the second case questions the nomenclature itself due to its metastatic potential. Whether the renaming of papillary microcarcinoma is justified and the role of ultrasound guided fine needle aspiration cytology (USG guided FNAC) in diagnosis of clinically non-apparent papillary carcinomas is addressed in this report.
Keywords: Metastases to cervical lymph nodes, papillary microtumor of thyroid, ultrasound guided fine needle aspiration cytology of thyroid
|How to cite this article:|
Kamath AS, Manjunatha H K, Ramaswamy A S, Nayak VJ. Papillary microtumor of thyroid: Benign or aggressive?. J NTR Univ Health Sci 2014;3:51-3
|How to cite this URL:|
Kamath AS, Manjunatha H K, Ramaswamy A S, Nayak VJ. Papillary microtumor of thyroid: Benign or aggressive?. J NTR Univ Health Sci [serial online] 2014 [cited 2020 Apr 4];3:51-3. Available from: http://www.jdrntruhs.org/text.asp?2014/3/1/51/128442
| Introduction|| |
Papillary microtumor (PMiT) of thyroid is defined as an incidentally discovered papillary carcinoma of thyroid that measures ≤10 mm (≤1 cm) in the greatest diameter, but not clinically evident small-sized papillary carcinomas.  It is a common incidental finding (25% or > depending on thoroughness of specimen examination).  PMiTs are known to present with secondaries in draining cervical lymph nodes with rare cases of distant metastases.  The increased detection rates of PMiTs has been attributed to the worldwide use of high resolution sonography and ultrasound guided fine needle aspiration cytology (USG guided FNAC) of thyroid.  Sixty-four cases have been reported in literature.
| Case Reports|| |
A 47-year-old female presented with swelling in front of the neck associated with difficulty in swallowing. On examination, the swelling moved upwards with deglutition and was localized more towards the right side of the midline. FNAC was advocated.
FNAC smears showed moderate cellularity and were composed of loose clusters of benign follicular epithelial cells with moderate amount of thin colloid and cyst macrophages in the background. A cytomorphological diagnosis of nodular goiter was offered. The patient was euthyroid and underwent hemithyroidectomy (right lobectomy with removal of isthmus).
Gross examination of the excised specimen showed two well-circumscribed nodules filled with colloid and surrounding tan brown areas. On microscopy, the area representing the isthmus showed a tumor with stellate configuration. The tumor cells were arranged in papillary architecture. The nuclei were typical of papillary carcinoma with pale nuclear chromatin, nuclear grooves, and intranuclear inclusions [Figure 1]. The rest of the thyroid tissue showed thyroid follicles of varying sizes filled with abundant bright eosinophilic colloid with focal areas showing degenerative changes. The final histopathological diagnosis was of latent PMiT within adenomatoid goiter.
|Figure 1: Papillary microtumor with stellate configuration (hematoxylin and eosin (H and E), ×10). Inset: Typical nuclear features of papillary carcinoma (H and E, ×40)|
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A 52-year-old female presented with cervical lymphadenopathy. On examination, the lymph node was hard in consistency. FNAC was advocated.
FNAC smears were cellular and showed tumor cells arranged in papillary pattern. The nuclei showed powdery chromatin with occasional nuclear grooves and intracytoplasmic inclusions. Cytomorphological diagnosis of highly suspicious for papillary carcinoma was offered.
The patient's thyroid showed neither enlargement nor any nodularity. An ultrasound scanning of the thyroid was advised which showed a tiny hypoechoic nodule measuring ≤10 mm (≤1 cm). USG guided FNAC of the thyroid was done which showed cytomorphological features of papillary carcinoma [Figure 2]. A final diagnosis of occult papillary microcarcinoma of thyroid was offered.
|Figure 2: Patient presenting with cervical lymphadenopathy and clinically non-apparent thyroid. Inset: Fine needle aspiration cytology (FNAC) smear showing papillary carcinoma (May-Grünwald-Giemsa (MGG), ×40)|
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| Discussion|| |
PMiT of thyroid is synonymous with small papillary carcinoma,  occult sclerosing carcinoma, and nonencapsulated sclerosing tumor. , PMiT is a common incidental finding at autopsy and in thyroid gland removed for other reasons like in thyroidectomy for benign disease and completion thyroidectomies in patients with a history of carcinoma involving the opposite thyroid lobe. ,
The Porto proposal, 2003 renamed this entity as PMiT of thyroid. Previously called as papillary microcarcinoma of thyroid. It also recommended certain guidelines in the diagnosis of PMiT which are as follows. ,
The term PMiT is to be employed only for adult patients and that papillary neoplasms occurring in children are designated as papillary carcinomas regardless of size.
Whenever two or more lesions with the appearance of PMiT are detected, the possibility must be considered that they represent intrathyroid spread from a separate primary thyroid carcinoma. If no such primary can be found and the lesions are morphologically typical of PMiT, a diagnosis of multicentric PMiT can be made.
Occasionally, lesions fulfilling the criteria for PMiT are found entirely confined within benign thyroid nodules having otherwise typical features of follicular adenoma or hyperplastic (adenomatoid) nodule. These lesions are designated as "PMiT within".  In our case report 1, we have seen a similar case and reported it as latent PMiT within adenomatoid goiter. It was prefixed latent because, latent is the term used for papillary carcinomas discovered incidentally in thyroidectomy or lobectomy specimen or at autopsy and they may or may not be micropapillary carcinomas.  Postoperatively, the patient underwent ultrasound scanning of the remaining thyroid tissue for any evidence of multicentric foci and was found to have no abnormality. She was advised for routine follow-up because of the risk of metastases at a later date.
If a papillary carcinoma of less than 1 cm diameter is found incidentally at radiologic examination performed for some other reason, it should still be classified as PMiT. Conversely, if the tumor were to be found in the course of an investigation carried out because of the presence or suspected presence of metastases, the use of the term PMiT is not recommended.  In our case report 2, the patient presented with cervical lymphadenopathy and USG guided FNAC conducted after a suspicion of metastatic papillary carcinoma yielded occult papillary microcarcinoma of thyroid. It was prefixed occult because, occult is the term used for papillary carcinomas found in thyroid subsequent to discovery of metastatic tumor. 
USG guided FNAC has been advocated for small thyroid nodules regardless of the nodule size when it is necessary to determine the type of thyroid surgery (a total thyroidectomy or hemithyroidectomy), if the primary thyroid malignancy is a papillary thyroid carcinoma and is <10 mm in maximal diameter.  In our case, no further intervention was done as the patient was not willing for surgery.
A similar case presenting with axillary lymphadenopathy later diagnosed as papillary microcarcinoma of thyroid was seen by the authors. 
The entity PMiT of thyroid is preferred over papillary microcarcinoma of thyroid as it has an excellent prognosis and no additional therapy is required. , It also decreases the danger of overtreatment and minimizes the psychologic anxiety engendered by a diagnosis of carcinoma.  However, usage of the term papillary microcarcinoma should not be aborted because of the metastatic potential of these tumors stressing the importance of role of ultrasound scanning in clinically non-apparent papillary carcinomas and routine follow-up.
Our cases emphasize the awareness of the new entity and discuss the usage of both the terminologies, PMiT and papillary microcarcinoma of thyroid in different case scenarios. We advocate extensive sampling of routine thyroidectomy specimens. In suspected cases of metastatic, clinically non-apparent papillary carcinomas ultrasound scanning of the thyroid is a must to determine the tumor and the type of thyroid surgery. Routine follow-up is recommended, once a diagnosis of PMiT is made because of its metastatic potential.
| References|| |
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[Figure 1], [Figure 2]