| Abstract|| |
Follicular thyroid carcinoma (FTC) has been classified as either minimally invasive or widely invasive carcinoma and shows a propensity for blood-borne metastasis. Most common sites of metastasis are lung and bone followed by brain, liver, and skin. Minimally invasive FTC (MIFTC) is characterized by limited capsular and/or vascular invasion with good long-term outcomes, some cases of which show a poor prognosis because of severe distant metastasis. Skull metastasis in adults commonly arises from the lung, breast, and prostate and uncommonly from the thyroid. In our case, fine-needle aspiration cytology of isolated skull nodule was a reliable tool in the diagnosis of metastasis and suggesting the primary in thyroid thereby prompting early workup of a patient. The case is unique since it represents the rare disseminated metastasis from MIFTC with incomplete capsular penetration alone without angioinvasion that can behave as aggressively as a widely invasive FTC.
Keywords: Disseminated, metastasis, minimally invasive follicular thyroid carcinoma, thyroid
|How to cite this article:|
Gupta P, Bhardwaj M. Fine-needle aspiration cytology of isolated skull nodule: Unfolding the clinical spectrum. Indian J Pathol Microbiol 2016;59:401-3
|How to cite this URL:|
Gupta P, Bhardwaj M. Fine-needle aspiration cytology of isolated skull nodule: Unfolding the clinical spectrum. Indian J Pathol Microbiol [serial online] 2016 [cited 2020 Jul 5];59:401-3. Available from: http://www.ijpmonline.org/text.asp?2016/59/3/401/188133
| Introduction|| |
Skull metastasis in adults commonly arises from the lung, breast, and prostate and uncommonly from the thyroid. Follicular thyroid carcinoma (FTC) shows propensity for blood-borne metastasis. Minimally invasive FTC (MIFTC) is occasionally associated with metastasis, whereas cases with florid capsular and vascular invasion may or may not develop metastasis over the years. MIFTC has a good prognosis with an excellent long-term survival rate.
We report a case of a patient who presented with isolated solitary skull nodule, which on fine-needle aspiration cytology (FNAC) showed cells suggestive of metastasis from thyroid carcinoma. Subsequent radiological evaluation and FNAC from thyroid and other involved sites revealed follicular carcinoma thyroid with distant multiple metastasis comprising multiple bony lesions, liver, and soft tissue. Extensive histopathological grossing and sectioning of thyroid revealed MIFTC with incomplete capsular penetration only.
It was a rare case of disseminated metastasis arising from MIFTC without any angioinvasion and incomplete capsular penetration only, which we are probably the first ones to report. FNAC of the skull nodule was a rapid diagnostic tool in confirming the metastasis and suggesting the primary in thyroid leading to early workup of the patient.
| Case Report|| |
A 50-year-old male was referred from the neurosurgery outpatient department to the FNA clinic with complaints of gradually increasing swelling in the right forehead region. On examination, the swelling was 4 cm × 3 cm in size, soft, fixed, and nontender. There was no other systemic complaint. Contrast-enhanced computed tomography (CECT) head showed frontal region swelling with underlying bony lytic lesion and overlying soft tissue component with normal brain parenchyma [Figure 1]a. Radiological impression was suggestive of intraosseous primary meningioma or a metastatic mass. FNA was done using 22-gauge 1½” needle and 10 ml syringe and smears prepared were alcohol fixed and air-dried and stained with Papanicolaou and Giemsa stains, respectively.
|Figure 1: (a) Lytic lesion in the frontal bone with overlying soft tissue swelling (computed tomography scan). (b) Fine-needle aspiration smears revealed follicular cells forming microfollicles and in clusters (Giemsa, × 400)|
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The smears revealed variable cellularity in a hemorrhagic background comprising uniform round to oval cells with evenly distributed nuclear chromatin and scant cytoplasm in clusters and microfollicle formation [Figure 1]b. In view of these bland cytomorphological features and microfollicles, a possibility of metastasis from thyroid was considered on FNAC.
The patient was examined thoroughly, and mild enlargement of the left lobe of thyroid was noted along with a single subcutaneous lower back swelling measuring 1 cm × 1.5 cm. No other swelling or lymph node was palpable. Further, the CECT neck, chest, and abdomen revealed the left lobe malignant thyroid mass with retrosternal extension, distant multiple bony lytic lesions in ribs, spine of the left scapula, cervical and thoracic vertebra, left iliac blade, multiple well-defined space occupying hypodense lesions in liver, and fibro bronchiectatic changes in the lung [Figure 2]a, [Figure 2]b, [Figure 2]c. FNAC smears from thyroid and subcutaneous lower back swelling revealed cytomorphological features of follicular neoplasm [Figure 2]d. Ultrasound-guided FNAC from the largest liver lesion measuring 4 cm in diameter revealed only occasional preserved cluster of follicular cells in a necrotic background [Figure 2]e. Thus, it was a case of disseminated metastasis from FTC. The patient underwent total thyroidectomy, and histopathological examination of the thyroid revealed areas of adenomatous goiter and a solid hypercellular nodule. No mitosis or tumor necrosis was noted. Extensive grossing of the thyroid capsule and serial sectioning revealed a focus of mild mushrooming of the capsule and incomplete penetration by tumor cells [Figure 2]f. Thus, a diagnosis of minimally invasive follicular carcinoma of thyroid was offered.
|Figure 2: (a) Heterogeneously enhancing mass lesion in the left lobe of thyroid with calcification (computed tomography scan). (b) Expansile bony lytic lesion in the left scapula with heterogeneous enhancement (computed tomography scan). (c) Hypodense space occupying lesions in liver (computed tomography scan). (d) Fine-needle aspiration smear from thyroid swelling reveal features of follicular neoplasm (Pap, × 400). (e) Ultrasound-guided fine-needle aspiration smear from liver reveals occasional cluster of follicular cells in a necrotic background (Pap, × 400). (f) Mild mushrooming of the thyroid capsule showing incomplete tumor cell penetration (H and E, × 100)|
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| Discussion|| |
FTC accounts for 10–20% of all thyroid malignancies and distant metastases at the time of diagnosis are reported in 11–20% of patients. Most common sites of metastasis are lung and bone followed by brain, liver, and skin. Disseminated metastasis has rarely been reported. Synchronous lung and bone metastasis in follicular carcinoma have been reported in about 20% of FTC. The presence of distant metastasis is considered one of the most important indicators of unfavorable prognosis in differentiated thyroid carcinomas. Concurrent skull and liver metastasis from FTC is a very rare event and leads to a very dismal prognosis.
FTC has been further classified based on the extent of capsular and vascular invasion: MIFTC with capsular invasion only, with limited (≤3) vascular invasion, encapsulated FTC with extensive (>3) vascular invasion, and broadly invasive FTC with extensive invasive growth. MIFTC has a very favorable long-term prognosis with few recurrences and no distant metastasis, which allows the treating surgeon and endocrinologist to perform a lobectomy alone without additional surgery or adjuvant therapy. Although MIFTC is characterized by limited capsular and/or vascular invasion with good long-term outcomes, some cases of MIFTC show a poor prognosis because of severe distant metastasis.
Metastasis from MIFTC and encapsulated FTC has rarely been reported., Metastasis from MIFTC with incomplete capsular penetration alone without angioinvasion is very rare and was seen in our case.
Distant metastasis at diagnosis and large tumor size are significant prognostic factors of widely invasive FTC. Use of miRNAs as a novel biomarkers for the metastatic potential of MIFTC suggests that upregulation of miR-10b is a potential prognostic factor for evaluating the metastatic potential in MIFTC.
Our case is unique since it represents the metastatic MIFTC with incomplete capsular penetration alone involving distant multiple bony lytic lesions in ribs, spine of scapula, cervical and thoracic vertebra, iliac blade and skull along with liver, and soft tissue involvement. The literature mostly mentions about multiple metastasis from invasive FTC, and MIFTC is rare. To the best of our knowledge, we are the first ones to report such a disseminated metastatic pattern arising from a MIFTC with incomplete capsular penetration alone without angioinvasion.
The index case emphasizes the role of FNAC in the diagnosis and early workup of the patient presenting with skull nodule. Second, it confirms the metastatic potential of a minimally invasive FTC that can behave as aggressively as a widely invasive FTC.
It is suggested that further studies on FTC and the probable role of specific genetic alterations need to be documented to know the factor governing the metastatic behavior in MIFTC which otherwise is known to have a good prognosis.
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Conflicts of interest
There are no conflicts of interest.
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Dr. Prajwala Gupta
40/22, Ground Floor, East Patel Nagar, New Delhi - 110 008
Source of Support: None, Conflict of Interest: None
[Figure 1], [Figure 2]