Granular Cell Tumor: when should it be considered malignant? Immunohistochemical study of three cases

1. Granular Cell Tumor: when should it be considered malignant? Immunohistochemical study of three cases S.A. Senatore*, G.A. Colucci*, T.G. Carlà*, F. Floccari*, A.T. Pede*, E. Villani*, A. D’Amuri*° * U.O.C. Anatomia Patologica Ospedale “S. Cuore di Gesù” P.O. Gallipoli ASL/LE ° Dipartimento di Patologia Umana ed Oncologia Sez. Anatomia Patologica Università degli Studi di Siena

2. INTRODUCTION • Granular Cell Tumor (GCT) is a rare neoplasm which tends to occur throughout the dermis or subcutis with a predilection for the head and neck regions, soft tissue and mucosa of the aerodigestive tracts. • Visceral involvement is less frequent. • GCT are accepted as being of neural origin from the Schwann-cell owing to their peculiar ultrastructural features and immunohistochemical reactivity with S100 protein, neuron-specific enolase (NSE) and myelin–specific protein. • Malignant variants represent only 1% of all cases.

3. INTRODUCTION • Clinical manifestations are varied. Many present as pale white/yellow subcutaneous circumscribed nodules with a normal or thickened overlying skin. • The nodules can also be itchy or painful. • GCT may affect people of a wide age range with a peak of incidence in the 4th through 6th decades of life. • The only cure is local surgical excision of benign GCT while en bloc excision is recommended for malignant lesions which are not sensitive to radiation and chemotherapy.

4. CASE REPORTS • CASE 1: A 39-year-old white man presented to the ORL Division for a dysphonia due to a small nodule of the larynx which was subsequently surgically treated. • CASE 2: A 50-year-old white woman underwent clinical evaluation in the Surgical Division for the presence of a non-ulcerated nodule on the anterior dorsal surface of the tongue which was surgically excised. • CASE 3: A 76-year-old white man presented to the Surgical Division for the evaluation of a nodular lesion located beneath the surface epithelium of his back. Because of the suspicion of a melanoma, he was referred to a surgical management.

5. SURGICAL FEATURES • CASE 1: The observed specimen consisted of numerous fragments. The estimated size of the biggest one was of 1,3 x 0,8 cm and had a whitish appearance. • CASE 2: The lesion consisted in a whitish fragment of 1,3 x 0,8 cm. • CASE 3: Grossly, the excised specimen consisted of a yellowish lozenged-shaped cutis of 3 x 1,4 cm. The nodular lesion had a maximum diameter of 1,2 cm.

6. MATERIALS & METHODS • Specimens were fixed in 10% buffered formalin and paraffin embedded. 5m serial sections were obtained and routinely stained with hematoxylin-eosin (H/E) and PAS histochemical reaction. • Immunohistochemical studies were performed for Alpha 1 AT, CD68, Citokeratin AE1/AE3, HMB45, Ki-67, Lysozyme, NSE, S100 protein and Vimentin.

7. H/E S100 NSE Ki-67 CASE 1

8. MICROSCOPICAL FINDINGS: CASE 1 • The H/E stained section revealed a nodular neoformation constituted by typical granular cells showing vescicolous nuclei with an optically empty appearance cytoplasm. • Immunohistochemical stains for S100, NSE, CD68, Vimentin and a1AT were found positive. On the contrary Ki-67 had a very low proliferative index (≥ 2%). • A diagnosis of GCT was performed.

9. S100 NSE Ki-67 CASE 2

10. MICROSCOPICAL FINDINGS: CASE 2 • The histological examination revealed a subepidermical pseudo-nodular neoformation constituted by typical granular cells showing vescicolous nuclei with abundant cytoplasm. Morphological atypia was also noted. • Immunohistochemical stains for S100, NSE, CD68, Vimentin and a1AT were found positive. Ki-67 had a low proliferative index (≤ 5%). • The O.M. diagnosis of GCT was made and later confirmed by TEM evaluation.

11. H/E S100 Ki-67 NSE CASE 3

12. MICROSCOPICAL FINDINGS: CASE 3 • The H/E stained section demonstrated a subepidermical nodular cutaneous formation extended to medium derma, formed by atypical pleomorphic elements showing vescicolous nuclei, nucleolated with high mitotic index, an eosinophilic granular cytoplasm, sometimes microvacuolar with an optically empty appearance. • Immunohistochemical stains for Vimentin, S100, NSE, 1AT, CD68 were strong and diffusely positive. Ki-67 had a high proliferative index (> 50%). • The reported morphofunctional observations gave evidence for a malignant cutaneous tumor with pleomorphic granular elements (MGpCT).

13. DISCUSSION • The neoplasms observed are of Schwann cell origin and our diagnosis is based on their histological features and immunohistochemical reactivity with S100 protein and NSE. Ki-67 can predict the clinical behaviour and, as reported in previous studies, a rare immunostaining was found in the benign form of GCT (as showed in our 1st and2nd cases). • The distinction between benign and malignant GCT is controversal because of histological similarities. By convention, GCT are classified as malignant when the constituent cells show cytological features of malignancy or when a morphologically benign GCT metastasizes to regional lymph nodes or distance sites or otherwise causes death.

14. DISCUSSION • The histological criteria for a malignant classification are based on the presence of necrosis, spindling of tumor cells, vescicular nuclei with large nucleoli, increased mitotic activity, high nuclear to cytoplasmic ratio and pleomorphism. Neoplasms that meet three or more of these criteria can be classified as histologically malignant. Our 3th case completely satisfies the reported criteria. • Our results could also suggest that, in the absence of “strictly malignant” morphological criteria, the diagnostic immunealgorithm has no prognostic relevance. • Finally in the 3th cases observed, in which Ki-67 presents an increased proliferative index, might be able to define a high malignant potential GCT.

15. REFERENCES Fanburg-Smith J.C. et al. Malignant granular cell tumor of soft tissue: diagnostic criteria and clinicopathologic correlation. A J Surg Pathol 1998, 22 (7): 779-794. Miracco C. et al. Granular cell tumor with histological signs of malignancy: report of a case and comparison with 10 benign and 4 atypical cases. Br J Dermathol 1999, 141 (3): 573-575. Le B.H. et al. Granular cell tumor immunohistochemical assessment of inhibin- protein gene product 9.5, S100 protein, CD68 and Ki-67 proliferative index with clinical correlation. Arch Pathol Lab Med 2004, 128: 771-775.