Atypical granular cell tumor of the thyroid: Cytomorphologic features on fine needle aspiration

Abstract

Granular cell tumors are uncommon soft tissue neoplasms of nerve sheath origin, which are predominately benign and are characterized by abundant granular cytoplasm, uniform nuclei, and indistinct cell borders. Features of malignancy include spindle cell morphology, necrosis, prominent nucleoli, increased nuclear to cytoplasmic ratio, nuclear pleomorphism, and increased mitotic rate. Granular cell tumors are most common in the soft tissues of the head and neck, but have only been rarely described in the thyroid gland. Here we report a case of an atypical granular cell tumor of the thyroid seen on fine needle aspiration, which displayed focal atypical cells with spindle cell morphology, increased nuclear to cytoplasmic ratio, and prominent nucleoli. The differential diagnosis of such findings is also presented.

Fine needle aspiration cytology of a granular cell tumour arising in the thyroid gland

“…GCTs are thought to arise from peripheral nerve sheath cells, but are associated with both neural and histiocytic differentiation. The cytological features previously reported are similar to our thyroid GCT findings: large cells with abundant granular cytoplasm with indistinct borders and fairly uniform, generally spherical small nuclei with inconspicuous nucleoli, and a background of naked nuclei with granular debris 3,4 …”

“…To our knowledge, eight primary GCTs of the thyroid gland have been previously reported; only two of the reports described cytological findings obtained by fine needle aspiration (FNA). 3,4 We describe a case of thyroid GCT together with its radiological [computed tomography (CT) and sonography] and cytopathological characteristics.…”

“…The cytological features previously reported are similar to our thyroid GCT findings: large cells with abundant granular cytoplasm with indistinct borders and fairly uniform, generally spherical small nuclei with inconspicuous nucleoli, and a background of naked nuclei with granular debris. 3,4 Pre-operative diagnosis of GCT in unusual locations by cytological screening is difficult. In cytological evaluations, the tumour cells may be differentiated from common thyroid lesions with cytoplasmic granules, such as Hü rthle cells, macrophages and follicular cell lesions.…”

FNA of thyroid granular cell tumor

“…Granular cell tumor is a relatively rare tumor, but it gains notoriety from its tendency to present in a variety of locations. There are only a few previously reported cases of granular cell tumor arising in the thyroid gland . This finding is of particular interest for a number of reasons.…”

“…While it has been reported to occur in many locations, the head and neck region is the most common. However, tumors arising from the thyroid gland are unusual . Because of the frequency with which neck masses present, it is important to be aware of the potentially peculiar presentation of this notable entity.…”