|LETTER TO THE EDITOR
|Ahead of print publication
Isolated dural metastasis of follicular carcinoma of the thyroid presenting as scalp swelling
Vikram Singh1, Apinderpreet Singh2, Sanjay Kumar Bhadada3, Ritambhra Nada1
1 Department of Histopathology, Post Graduate Institute of Medical Education and Research, Chandigarh, India
2 Department of Neurosurgery, Post Graduate Institute of Medical Education and Research, Chandigarh, India
3 Department of Endocrinology, Post Graduate Institute of Medical Education and Research, Chandigarh, India
Department of Histopathology, Postgraduate Institute of Medical Education and Research, Chandigarh
Source of Support: None, Conflict of Interest: None
Most patients with follicular carcinoma of the thyroid present with a thyroid mass, but up to 11% of patients present with the first presentation with distant metastasis, such as bone pain, fracture, or a pulsatile mass in soft tissue. In contrast to papillary carcinoma, the main mode of spread in patients of follicular carcinoma is hematogeneous (predilection sites being bone and lung) rather than lymphatic.
Skull metastasis of extracranial origin is rare. The most common malignancies which metastasize to the skull are lung, breast, and prostate carcinomas. Metastasis in the skull associated with carcinoma of the thyroid accounts for only 2.5%–5.8% of cases, but the initial presentation with distant metastasis is rare. Isolated metastatic tumoral nodules have a radiological feature that strongly suggests a primary tumor, and furthermore, their macroscopic appearance during surgery may even be taken for a meningioma.
We are presenting an interesting case of follicular carcinoma thyroid, who presented as isolated calvarial metastasis in the form of scalp swelling and mimicked a meningioma. A 60-year-old female, a known case of goiter with hypothyroidism for 10 years and receiving Eltroxin, presented to the neurosurgery outpatient department with a complaint of left-sided scalp swelling measuring 11 cm × 9 cm, associated with headache and generalized weakness. There was no history of nausea and vomiting. Higher mental functions and cranial nerve examination were with normal limits. All the baseline investigations were within normal limits. Contrast-enhancing magnetic resonance imaging and computed tomography angiography showed left frontal calvarial mass approximately measuring 10 cm × 8 cm in size [Figure 1]a and [Figure 1]b. Fine-needle aspiration cytology was done from the scalp lesion, and it was suggestive of secretory meningioma. In view of clinical and imaging findings, preoperative diagnosis of the left frontal calvarial metastasis was made with differential of meningioma. Intraoperative, a tumor was identified extending from dura to both frontal bone and anterior part of the left parietal bone and causing destruction of bone. Gross total excision of the tumor was done followed by duraplasty.
|Figure 1: Radiological and gross image (a) magnetic resonance imaging of calvarial mass showing a left frontal region tumor measuring 10 cm × 8 cm in size, (b) computed tomography angiography of calvarial mass showing a left frontal region tumor measuring 10 cm × 8 cm in size, (c) gross image of excised tumor mass showing a tumor, which is eroding through the calvarial bone|
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We received a bony fragment measuring 12 cm × 6 cm × 4 cm, with firmly adherent nodular lesion measuring 9 cm × 5 cm × 3 cm, which was eroding through the calvarial bone [Figure 1]c.
On microscopy, a tumor was seen arranged in the form of well-formed back to back arranged follicles filled with colloid-like material [Figure 2]a. These tumor cells were moderately pleomorphic with round-to-oval nuclei, inconspicuous nucleoli, and moderate cytoplasm. These tumor cells were suspicious of follicular carcinoma of the thyroid. Tumor cells were seen infiltrating through the dura mater and bone [Figure 2]b.
|Figure 2: Histological and immunohistochemistry images (a) hematoxylin and eosin, ×10 showing a tumor with well-formed follicles filled with colloid (b), hematoxylin and eosin stain, ×10 showing tumor infiltrating through the bone, (c) thyroid transcription factor-1 immunostain, ×10 showing nuclear positivity in metastatic thyroid follicular carcinoma cells, (d) thyroglobulin immunostain, ×20 showing strong cytoplasmic positivity in metastatic thyroid follicular carcinoma cells|
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Thyroid origin was confirmed by positive immunohistochemistry for thyroid-associated antigens, i.e., thyroglobulin and thyroid transcription factor-1, confirming the diagnosis of metastatic thyroid carcinoma [Figure 2]c and d]. Based on histopathology report, ultrasonography of the thyroid gland was done and it was suggestive of malignant lesion. Fluorodeoxyglucose (FDG) positron emission tomography scan did not show any FDG-avid lesion anywhere in the body. Postoperative period was uneventful, and the patient is now planned for thyroid surgery.
Metastasis in the skull associated with carcinoma of the thyroid accounts for only 2.5%–5.8% of cases, but the initial presentation with distant metastasis is rare. In a study by Venkatesh et al., eleven patients developed brain metastases from well-differentiated thyroid carcinoma 1–20 years after their original diagnosis. Two had only brain metastases and nine had metastases to the lungs and bones as well.
Our case is a rare case of follicular thyroid carcinoma with calvarial metastasis, presenting as a scalp swelling which mimicked a meningioma. Histomorphological identification of lesions along with the use of diagnostic immunohistochemistry is the key to diagnosis of tumors present in odd sites and is important to channelize treatment in the right direction. Metastatic follicular carcinoma should be kept in mind in the differential diagnosis of scalp swelling, especially in those patients who have a long history of goiter.
Declaration of patient consent
The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.
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Conflicts of interest
There are no conflicts of interest.
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