Follicular thyroid carcinoma - spinal metastasis

Case contributed by Dr Bruno Di Muzio

Presentation

Backpain.

Patient Data

Age: 80 years
Gender: Female

Right-sided small pleural effusion associated with diffuse pleural thickening,  there is no pleural surface nodularity to suggest malignancy.  Round atelectasis within the right medial and lower lobes, with a few flecks of calcification within the collapse portions.  There has been significant improvement of the left sided effusion compared to prior imaging (not shown), now only showing a small trace at the bases.  Focal atelectasis within the left lower lobe.  The lungs are otherwise clear, no suspicious lesions identified.

There are two prominent right upper mediastinal lymph nodes measuring up to 1.2 cm in the short axis.  Multinodular goiter.  The mediastinal structures have otherwise unremarkable appearances.

There is a soft tissue mass partially destructing the T8 vertebral body and extending anteriorly/to the right, bulging against the esophagus.

Conclusion:
1. T8 vertebral body malignant lesion likely reflecting metastatic deposit. Bone scan/PET-CT recommended to asses if this is a solitary skeletal lesion.
2. Right upper mediastinal enlarged lymph nodes are indeterminate.
3. Persistent small right-sided effusion and pleural thickening, but no pleural nodularity.
4. Multinodular goiter. This can be further assessed with a neck ultrasound, if not yet investigated.

Nuclear medicine

18FDG PET-CT

Single bone metastatic deposit and right thyroid/isthmus FDG avid lesions. 

Ultrasound

Thyroid

The right thyroid lobe measures 2.2 x 4.5 cm.
The left thyroid lobe measures 2.4 x 2.4 cm.
The isthmus measures 0.7 cm in thickness.

Multinodular goiter with the largest lesion in the isthmus measuring 2.9 cm.  This is almost completely solid and hypoechoic relative to the surrounding thyroid parenchyma taller than wide with irregular lobulated margins (TIRADS 5).

Multiple further nodules are noted bilaterally. A 1.2 cm nodule in the right upper pole of the demonstrate mixed solid and cystic composition with hypoechoic echotexture (TIRADs 3).

No lymphadenopathy in the neck.

Comment:
Multinodular goiter with a suspicious nodule at the isthmus measuring 2.9 cm (TIRADs 5). An FNA of this nodule is recommended.

CT-guided spinal metastasis biopsy was performed.

Macroscopy: Labelled "T8 vertebral body biopsy". Bony tan core biopsy 6mm with small fragments 1mm to 3mm.  Specimen treated in decalcification fluid before processing. 

Microscopy: Sections show necrotic bony fragments focally showing closely compact glandular structures lined by mildly pleomorphic epithelium are with central eosinophilic material within the lumen of the closely compact glands. Immunoperoxidase is required for further differentiation of potential primary

Conclusion: T8 vertebral body biopsy–metastatic moderately well-differentiated adenocarcinoma. The morphology is in keeping with follicular thyroid carcinoma.

The tumour cells are immunoreactive with thyroglobulin, TTF-1, CK 7 and do not immunoreactive with cytokeratin 20. The findings are in keeping with metastatic follicular carcinoma of the thyroid.

Further thyroidectomy was performed: 

Macroscopy: A. Labelled "Left hemithryoidectomy. Short sup long lat". A lobe of thyroid 17 g and 53 x 28 x 25 mm (S/I x M/L x A/P), with pyramidal lobe 30 x 9 x 7 mm. There is a short suture present at the tapered aspect of the lobe indicating superior, and a long suture along one long edge indicating lateral. The thyroid capsule is grossly intact. Pretracheal surface inked black. Medial edge inked blue. Remaining tissue inked green.  Sectioning reveals multiple cystic/gelatinous colloid nodules, up to 15 mm.  There no encapsulated or firm lesions. The remaining thyroid parenchyma is red/brown and moderately firm. Part processed. B. Labelled "Right hemithyroidectomy. Short sup long lateral".A lobe of thyroid 23 g and 55 x 38 x 25 mm (S/I x M/L x A/P). There is a short suture present at the tapered aspect of the lobe indicating superior, and a long suture along one long edge indicating lateral. The thyroid capsule is grossly intact. Pretracheal surface inked black. Medial edge inked blue. Remaining tissue inked green.  There is a firm lobulated white nodule occupying the inferior portion of the lobe 28 x 27 x 21 mm.  The nodule abuts the capsule anteriorly and posteriorly and at the inferior pole.  Several scattered colloid nodules are present throughout the remaining parenchyma 3-8mm. The remaining thyroid parenchyma is red/brown and moderately firm. Part processed.

Microscopy: A. Sections show thyroid lobe with multiple rounded nodules with macrofollicular architecture. There is patchy interstitial fibrosis and evidence of prior haemorrhage. Partial cystic degeneration is evident. Follicular epithelial cells have regular, round nuclei. No parathyroid tissue is identified. There is no malignancy. B. Sections show thyroid lobe with multiple hyperplastic nodules, features as described above (specimen A). There is also a highly cellular neoplasm with microfollicular architecture broadly invading the surrounding thyroid parenchyma as multinodular protrusions extending from the main rounded mass. The majority of the tumour consists of tightly packed microfollicles, with focal trabecular growth. The tumour cells generally have round nuclei, with mild nuclear membrane irregularity. A focus of vascular invasion is identified, confirmed with a CD31 immunostain (B6). No intranuclear inclusions or papillary growth is evident. There are focal calcification and sclerosis at the tumour periphery. Tumour is clear of resection margins and no extrathyroidal tumour extension is seen. No parathyroid tissue is identified.

Conclusion: Total thyroidectomy specimen:
Follicular thyroid carcinoma, widely invasive, 28 mm in size, in the right lobe.
- Vascular invasion present.
- No microscopic extrathyroidal tumour extension.
- Resection margins clear.
Surrounding thyroid shows features of nodular hyperplasia.

Case Discussion

Unlike the much more common papillary carcinoma, follicular thyroid carcinoma metastasizes late to lymph nodes, with only 5-10% of patients having nodal metastases at the time of diagnosis. Haematogenous spread, as in this case, is however much more common with 20% or so of patients having distant haematogenous metastases at presentation.

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Case information

rID: 74526
Published: 27th Apr 2020
Last edited: 27th Apr 2020
System: Chest
Inclusion in quiz mode: Included