Giant Schwannoma

ARTICLE

A 16-year-old Japanese boy presented with a tumor on the left side of his back. His mother had noticed it when he was a baby. Since then, it had gradually increased to 31 x 18 x 3 cm in size. It was pale blue, elastic soft, and lobular (Fig. 1). On its top, there was a red nodule. A sensory abnormality and hypohidrosis were detected at the lesion site (Fig. 2), but laboratory findings were within normal limits. In a CT examination of the lesion, the skin overlaying the lesion was found to be thicker than normal skin, and an isodensity tumor was present at subcutaneous level. It was situated close to the muscle (Fig. 3).

Giant Schwannoma

Light microscopy

Numerous cellular nests encapsulated with thin connective tissue were present in the dermis and subcutaneous fatty tissue. In the dermis, eccrine sweat glands were closely surrounded by the tumor mass and intradermal ducts were not seen in the upper dermis (Fig. 4). Tumor nests were composed of Antoni A type tissue. The nuclei of the tumor cells were spindle-shaped or elongated in a palisading arrangement. In the center of the double palisade was the so-called verocay body (Fig. 5): Tumor cells were strongly positive for S100-protein.

Electron microscopy

Spindle-shaped cells containing elongated nuclei were closely packed and arranged irregularly (Fig. 6). In the intercellular spaces of the tumor cells, homogeneous dark material was present. The cavities of the eccrine sweat glands were narrowed and slightly occluded. Nerve endings were not observed arund the glands (Fig. 7).

Comment

Schwannoma is a benign nerve sheath tumor, that usually occurs as solitary encapsulated subcutaneous tumor adherent to a peripheral nerve. It is a common cutaneous tumor [1]. But there have been very few reports of giant schwannoma. Only 7 cases, including ours, have been reported over the past 5 years in Japan [2]. Harkin et al. stated that schwannoma rarely became larger than 8 cm in diameter [3]. In our case, hypohidrosis was recognized overlaying the tumor. We observed the eccrine glands and the surrounding tissue histopathologically and by electron microscopy. Histopathologically, some eccrine sweat glands were in close contact with the tumor nests and intradermal sweat ducts were not observed in the upper dermis. Ultrastructurally, cavities of eccrine sweat glands were narrowed and slightly occluded, and nerve ending were not seen around the glands. Rook indicated that hypohidrosis may be due to an abnornality of the sweat gland itself or an abnormality of the nerve pathway [4]. Hypohidrosis was recognized in the skin verlaying the tumor. These findings suggest that the autonomic nerve endings and sweat ducts in the dermis disappeared due to the pressure of the tumor mass resulting in hypohidrosis in the skin of the lesion.

REFERENCES

1. Masson P. Experimental and spontaneous schwannoma. Am J Pathol 1932; 8: 67-88.

2. Hagiwara K. A case of a giant schwannoma on the extremities. J Dermatol 1993; 20: 700-2.

3. Harkin JC, Reed RJ. Tumors of the peripheral nervous system. Atlas of Tumor Pathology, Fasicle 3, Armed Forces Institute of Pathology, Washington DC, 1969: 29-51.

4. Champion RH. Textbook of Dermatology. 6th edition, vol. 3, Rook et al., Blackwell Science, 1998: 1985-99.