Treatment

Under local anesthesia, an incision through the mucosa was performed where an encapsulated brown to purple nodule was released (Figure 3).

Figure 3 This photograph is of the gross specimen that shelled out easily. It is encapsulated, smooth-surfaced, brown to purple in color, and measures 1.3 x 1.3 x 1.0 cm at its greatest dimensions.

Excisional Biopsy

Histologic examination reveals a trisected piece of soft tissue composed of an encapsulated neoplasm of clear cell origin (Figures 4-6). The neoplastic cells are arranged in alveolar clusters surrounded by a prominent vascular component. The cells have clear cytoplasm and oval to round nuclei. They are well differentiated and show no evidence of atypia. The immunohistochemistry stain is positive with antibody to Pax8 (Figure 8) and pancytokeratin (Figure 7) and is negative with antibody to S-100, 1A4 (smooth muscle actin) and HMB 45/50.

Figure 4 Low power (x40): the H & E histology reveals an encapsulated neoplasm of clear cell origin. The neoplastic cells are arranged in alveolar clusters surrounded by a prominent vascular component. The cells have clear cytoplasm and oval to round nuclei. They are well differentiated and show no evidence of atypia.

Figure 5 Low power (x100): the H & E histology reveals a neoplasm of clear cell origin. The neoplastic cells are arranged in alveolar clusters surrounded by a prominent vascular component. The cells have clear cytoplasm and oval to round nuclei. They are well differentiated and show no evidence of atypia.

Figure 6 High power (x200): the H & E histology reveals a neoplasm of clear cell origin. The neoplastic cells are arranged in alveolar clusters surrounded by a prominent vascular component. The cells have clear cytoplasm and oval to round nuclei. They are well differentiated and show no evidence of atypia.

Figure 7 Low power (x100): the immunohistochemistry stain reveals the cytoplasm of the clear neoplastic cells to be positive with antibody to pancytokeratin (AE1/AE3).

Figure 8 Low power (x100): the immunohistochemistry stain reveals the nuclei of the clear neoplastic cells to be positive with antibody to Pax8.