INVASIVE FOLLICULAR THYROID CARCINOMA PRESENTING AS LARGE SCAPULAR MASS WITH ROTATOR CUFF MUSCLE INVOLVEMENT

Abstract

INTRODUCTION
Follicular carcinomas occur in women beyond the 5th decade of life as a slow-growing thyroid nodule. Known to invade locally and metastasize distantly, direct extrathyroidal extension is possibly seen in its rarer widely invasive form. Common sites for metastases are lungs and bones. The bones often involved are vertebrae, long bones and flat bones particularly pelvis, sternum, and skull. Metastasis to scapula is an infrequent presentation and skeletal muscle metastasis is extremely rare. We present a rare case of metastatic follicular thyroid carcinoma that initially presented as a large right scapular mass.

CASE
 A 65-year-old female presented with a right scapular mass. MRI revealed a huge (22.2x13.5x13.8 cm) lobulated mass with central necrosis and non-delineation of the 4 rotator cuff muscles, thus she was referred to an orthopedic surgeon. Biopsy of the scapular mass showed findings consistent with invasive metastatic follicular carcinoma. Thyroid ultrasound revealed a right thyroid nodule measuring 3.55x3.52x2.72 cm and few subcentimeter nodules on the left lobe. Initial thyroid function tests showed low FT4 2.43 pmol/L (NV:11-22.5), normal TSH 2.374 (NV:0.30-5 mIU/mL) and FT3 5.96 (NV:3.1-6.5 pmol/L). The patient underwent total thyroidectomy and subsequent right total scapulectomy with biceps tendon transplantation attached to the clavicle. Histopathologic reports from both operations are consistent with widely invasive follicular carcinoma. The patient is scheduled for radioiodine therapy.

CONCLUSION
Soft tissue metastasis is an uncommon initial presentation of follicular thyroid carcinoma. Synchronous metastases to bones and soft tissues particularly on the scapula and surrounding muscles are rare occurrences that warrant this report.