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Chủ Nhật, 6 tháng 4, 2014

THYROID HEMANGIOMA






Discussion

Thyroid hemangiomas are extremely rare, and there are only a few cases reported in literature reviews. Most thyroid hemangiomas are not palpable and are diagnosed incidentally during imaging examinations. A hemangioma is a benign vascular tumor of 2 common types, capillary and cavernous, based on the size of the vessels involved. In most cases, thyroid hemangiomas are secondary to trauma or fine-needle aspiration biopsy. Secondary hemangiomas have been described as pseudomalformations, representing vascular proliferation after organization of a thyroid hematoma.Two case reports described exuberant vascular proliferation in the thyroid occurring secondary to fine-needle aspiration. Organization of the hematoma generally results in complete resolution, but it can give rise to vascular and fibroblastic proliferative changes that resemble a cavernous hemangioma. Our patients had no history of trauma, fine-needle aspiration, biopsy, or other invasive procedures in the neck; therefore, we believe that our cases were primary thyroid hemangiomas. Primary hemangiomas are extremely rare developmental anomalies resulting from the inability of the angioblastic mesenchyme to form canals. Previous studies reported that preoperative diagnosis of a thyroid hemangioma is difficult because there are no specific pathognomonic findings on sonography, fine-needle aspiration cytologic examination, or even CT. Heterogeneous signal intensity and a serpentine pattern on magnetic resonance imaging are considered highly suggestive of cavernous hemangiomas. However, there are a few reports of sonographic findings of hemangiomas in other superficial organs such as the breast. These studies reported that hemangiomas were lobulated, well-circumscribed masses, usually with heterogeneous or complex echogenicity due to the presence of multiple vascular channels and phleboliths. Our cases of thyroid hemangiomas showed well-circumscribed hypoechoic lesions with internal multiple linear septations on sonography, which were very similar to previously reported sonographic findings of hemangiomas. Another sonographic characteristic of a superficially located hemangioma is the compressibility of the blood-filled lesion unless it is fully thrombosed.  During the sonographic examinations, our lesions were compressible under the probe, and the lesion volume decreased after the bloody content was aspirated on fine-needle aspiration. We think that these lesions were vascular malformations such as hemangiomas based on the characteristic sonographic findings and confirmation of bloody content during fine-needle aspiration.

Innumerable internal septations on sonography may be related to the presence of multiple small vascular channels seen pathologically in hemangiomas, and large blood-filled spaces or sinuses have been previously reported in cavernous hemangiomas.Our cases were pathologically confirmed to be cavernous hemangiomas after surgery. Pathologically, cavernous hemangiomas are typically discrete multiloculated lesions containing evidence of hemorrhage in various stages of evolution. They lack smooth muscle and elastic fibers and are lined by a single layer of endothelium and differing quantities of subendothelial fibrous stroma. In most reported series, cavernous hemangiomas underwent periodic rapid growth, but in our first case, there was no interval change on follow-up sonography after 6 months or 1 year.

Coarse calcifications are often suggested to be a reliable sign of hemangiomas. However, in our cases, there was no sign of calcifications in the lesions on sonography or CT. Fine-needle aspiration cytologic examination seems to be inconclusive in the diagnosis of hemangiomas because it reveals only blood. Multiple fine-needle aspiration biopsies have not been shown to be useful in obtaining sufficient cellular material. However, we think that confirmation of bloody content by aspiration could be very helpful for preoperative diagnosis of thyroid hemangiomas when combined with characteristic sonographic findings. Core needle biopsy is usually contraindicated in hemangiomas because of the high risk of bleeding, but many hemangiomas have been diagnosed by core needle biopsies in intramuscular sites and the breast, and some authors suggest that core needle biopsy is a safe diagnostic procedure for hemangiomas. The definite diagnosis of a thyroid hemangioma is based on histologic findings. Complete surgical excision is usually recommended when a hemangioma is diagnosed.

Although there is the widespread perception that preoperative diagnosis of thyroid hemangiomas on sonography is difficult because there are no specific pathognomonic findings, we suggest that a more careful interpretation of sonograms with reference to characteristic imaging findings, such as a well-circumscribed hypoechoic structure with innumerable internal septations, may lead to a precise preoperative diagnosis of a thyroid hemangioma. In addition, although fine-needle aspiration cytologic results are usually insufficient, confirmation of bloody content during aspiration can further support a diagnosis of a thyroid hemangioma.

The presence of heterogeneous signal intensity and a serpentine pattern on magnetic resonance imaging is usually considered diagnostic for hemangiomas. Other imaging modalities such as single-photon emission CT, digital subtraction angiography, and red blood cell scans can provide additional information in the diagnosis of hemangiomas; however, such examinations are often not performed routinely because of their high cost and nonavailability, as in the cases described here.

Accurate preoperative diagnosis allows better preoperative planning, and adequate preoperative characterization is very important because bleeding is common in hemangiomas; in one series, intraoperative blood loss was in excess of 2 L. A previous report emphasized the importance of ensuring that the integrity of a thyroid hemangioma is maintained to minimize blood loss during surgery. 


This report describes 2 cases of thyroid hemangiomas that were diagnosed on sonography. These cases demonstrate that thyroid hemangiomas can be diagnosed correctly by sonography with or without confirmation of bloody content in the lesions by fine-needle aspiration.
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