BACKGROUND: Epithelioid schwannoma as a rare variant poses a challenge to all pathologists, as this uncommon entity is extremely difficult to conclusively diagnose by morphological analyses on a resected sample alone owing to its unique histopathological features. However, few papers have described the detailed clinicopathological characteristics of epithelioid schwannoma.
METHODS: A 65-year-old female presented with a history of a flat and slightly elevated firm and tan plaque accompanied by occasional tenderness, measuring 10 × 8 mm, in the right joint of her hand 1 year before resection. A gross examination of a locally resected specimen revealed an encapsulated nodular lesion, yellow-whitish in color, partly filled with blood. A microscopic examination showed that the tumor predominantly consisted of a solid proliferation of epithelioid cells having mildly enlarged and round to partially spindled nuclei and abundant vacuolated or clear cytoplasm with very few mitotic figures and modest nuclear size variation, associated with focal hyalinized, cystic and hemorrhagic degeneration. This well-demarcated tumor was surrounded by dense, hyalinized and layered fibrocollagenous stroma. Immunohistochemically, these tumor cells were diffusely positive for S-100 protein and had a very low MIB-1 labeling index, and type IV collagen was strongly reactive with reduplicated basal lamina of them. We ultimately made a diagnosis of cutaneous epithelioid schwannoma.
CONCLUSIONS: We should be aware that, since pathologists might misinterpret epithelioid schwannoma as other soft tissue tumors, including its malignant counterpart, a wide panel of immunohistochemical antibodies can be powerful supplementary tools for identifying a very rare entity of conventional schwannoma.

Schwannomas are mesenchymal neoplasms with a low malignant potential, which arise from Schwann cells. The tumors can occur in most parts of the body; however, the head, neck and flexor surfaces of the extremities are the most common locations. Schwannomas occurring in the hepatoduodenal ligament are extremely rare. To the best of our knowledge, only two cases of schwannoma in the hepatoduodenal ligament have been reported in the literature, and treatment of such cases by laparoscopic surgery has not yet been reported. The present study reports a case of schwannoma in the hepatoduodenal ligament in a 50-year-old male patient. Physical and laboratory examinations showed no abnormal results. Ultrasound and computed tomography failed to definitively diagnose the mass and identify its location. During laparoscopic surgery, a mass was identified in the hepatoduodenal ligament and was completely removed. The gross specimen was a 4.5×2.5×2.5-cm localized mass, yellowish-white in color. Microscopic examination revealed that the tumor was mainly composed of spindle-shaped cells and no atypical cells were identified. Immunohistochemical staining showed a strong positive S-100 protein reaction, whereas cluster of differentiation 34 and epithelial membrane antigen were negative. The final diagnosis of the lesion was benign schwannoma of the hepatoduodenal ligament. The patient was followed-up for 7 months and, at the time of writing, was healthy and without any complications. The aim of the present study was to describe a rare case of hepatoduodenal ligament schwannoma in a 50-year-old male patient, and present a review of the literature. To the best of our knowledge, this is the first case of hepatoduodenal ligament schwannoma treated by laparoscopic surgery.

The Schwannoma is a benign tumor that originates from Schwann cells of peripheral motor and sensory nerves. It presents as a solitary, slow growing, smooth-surfaced and asymptomatic firm mass. The pre-operative diagnosis is often difficult, and in majority of cases it can only be made during the surgery and the definitive diagnosis obtained by histological study when cells test positive for S-100 protein. In this report, a case of a 20-year-old female patient with a Schwannoma located in the upper gingival mucosa is discussed. The patient was referred to the department of oral and maxillofacial surgery with chief complaint of enlargement of the upper gingival mucosa at the level of upper right premolar. Clinical findings showed characteristics of connective tissue tumor including epulis; however, histologic and immunohistochemical studies revealed it to be a Schwannoma. There has been no sign of recurrence 1 year and 8 months after surgery.

Malignant gastrointestinal neuroectodermal tumor (GNET) is a rare soft tissue sarcoma, previously referred to as clear cell sarcoma-like gastrointestinal tumor (CCSLGT) and also commonly reported in the literature as clear cell sarcoma of the gastrointestinal tract (CCS-GI). The current study reports a case of GNET arising in the stomach of a 17-year-old male, who presented with symptoms of fatigue, anemia and low temperature. Examination with positron emission tomography-computed tomography revealed a soft tissue mass in the gastric antrum. Subsequently, radical distal gastric resection was performed, and the mass measured 6.0×4.0×3.5 cm3. Histopathological analysis revealed that the tumor cells were arranged in nests and focally formed fascicular, pseudopapillary, pseudoalveolar and rosette-like growth patterns. Osteoclast-like giant cells were also observed. Immunohistochemically, the tumor cells were positive for S-100 protein, vimentin and BCL-2, and negative for HMB45, Melan-A, CD117, CD34 and CD99. Additionally, the osteoclast-like giant cells were positive for CD68. Fluorescence in situ hybridization demonstrated EWSR1 gene rearrangement. After 10 months of follow-up, no evidence of recurrence or metastasis was observed. As GNET is currently classified differently and under various names in the literature, the information provided by this case study and review is predicted to be useful towards the accurate diagnosis, treatment and prognosis of this rare tumor type.

Schwannoma is a tumor originating from the Schwann cells. Gastrointestinal schwannomas are uncommon stromal tumors of the intestinal tract and, in particular, rectal schwannomas are extremely rare. In fact, it is well established that schwannomas appear more frequently in the stomach and in the small intestine, while location in the colon or in the rectum is uncommon. Reading the literature, only few cases of rectal schwannoma have been reported. Their diagnosis is confirmed by the immunohistochemical panel (S-100 protein). When these tumors are located in the colon and in the rectum, radical excision with wide margins is mandatory, due to their tendency to recur locally or become malignant, if left untreated. In the present study, we describe a case of a rectal schwannoma occured in a 72-year-old man, presented as a small polypoid lesion, which was successfully removed in toto by hot-biopsy, during the same endoscopy, due to the dimensons. No recurrence of the lesion was observed after 6 mo of follow-up.

A 78-year-old woman presented with an abdominal mass diagnosed by ultrasound and computed tomography. The patient underwent a laparotomy, during which a retroperitoneal tumor adherent to the cecum wall was identified. Microscopically, it showed spindle-cell proliferation in whorls, with low mitotic count (2 per 50 high-power fields) and was strongly positive for S-100 protein and vimentin. The final diagnosis was benign schwannoma of the cecum and no further treatment was required. Large intestine schwannomas are extremely rare tumors and only a few cases of schwannoma of the cecum have been reported to date.

Schwannoma is a benign, encapsulated, perineural tumor that arises from the Schwann cells. Approximately 25% of the reported cases originate from the head and neck region. Of these, approximately 1-12% occurs intraorally. The intrabony lesion accounts for less than 1% of the central neoplasms. We report a rare case of intraosseous schwannoma in an 8-year-old male patient characteristically originating from the mental nerve. Radiographic examination followed by histopathological evaluation was further confirmed by immunohistochemical markers, S-100 protein, and GFAP that stained intensely positive for the tumor. Thus, confirming the diagnosis of intraosseous schwannoma.