Primary intraosseous hybrid nerve sheath tumor of femur: a hitherto undescribed occurrence in bone with secondary aneurysmal bone cyst formation resulting in pathological fracture.

Soft tissue perineurioma besides its pure form may coexist with schwannoma as hybrid nerve sheath tumor (HNST) which occurs in the limbs, head and neck, trunk and occasionally colon but origination in other organ sites has not been reported. We report the first case of primary intraosseous HNST. An 18-year-old man suffered from pathological fracture of his right femur after an impact which was preceded by a similar episode two weeks previously. Plain radiograph revealed a displaced fracture in the superior diaphysis of the right femur where an expansile osteolytic lesion with relatively well defined borders was seen. Histologic examination of the curetted lesion showed a well circumscribed spindle cell neoplasm displaying predominantly storiform but focally whorled patterns. In areas, the cells possessed thin wavy spindle nuclei and delicate elongated bipolar cytoplasmic processes supported in a fibromyxoid stroma. They stained positively for EMA, claudin, CD34, collagen 4 and focally for S100 but negatively for MUC4 and BCL-2, indicative of perineurial differentiation. Situated in the periphery of some of these perineurial whorls are spindle cells bearing plump tapering wavy nuclei and palely eosinophilic cytoplasm with indistinct cell borders. They stained intensely for S100 but negatively for EMA, claudin, CD34, collagen 4, MUC4 and BCL-2, consistent with schwannian differentiation. Focally, these two varieties of cells intimately intermingled with each other. Features of aneurysmal bone cyst (ABC) formation were present but no mitotic figures, establishing the final diagnosis of primary intraosseous HNST with secondary ABC formation. The patient remained well 7 months after curettage and internal fixation of his fracture.

Chow LT 《-》

Hybrid schwannoma/perineurioma: clinicopathologic analysis of 42 distinctive benign nerve sheath tumors.

Hornick JL ，Bundock EA ，Fletcher CD 《-》

Primary intraosseous hybrid epithelioid schwannoma/perineurioma in the proximal tibia: a case report of benign hybrid neoplasm with local hypercellularity.

Lang Y ，Liu D ，Xiang P ，Wang J ，Li Y ... -  《Diagnostic Pathology》

[Hybrid schwannoma/perineurioma: a clinicopathological analysis of 35 cases].

Jiang XB ，Zhang L ，Sun M ，Zhao L ，Lao QY ，Yu L ，Wang J ... -  《-》

Congenital melanocytic nevus with features of hybrid schwannoma/perineurioma.

Neural differentiation by melanocytic nevi represents a well-recognized phenomenon, and melanocytic nevi with perineurial differentiation have been reported recently. We reported a case of a congenital melanocytic nevus with histopathologic features of hybrid schwannoma/perineurioma. The patient was a 36-year-old male who presented with a black tumor on his arm since birth. Histopathology showed a congenital melanocytic nevus in the superficial dermis, but more strikingly, in continuity with the melanocytic nevus, there was a well-circumscribed but unencapsulated nodule in the deep dermis. The nodule was composed of cellular and myxoid areas with storiform, laminated or whorled growth patterns. The cellular area was mainly composed of proliferation of plump spindle, oval or epithelioid cells. The myxoid area was mainly composed of proliferation of slender spindle cells with mucin deposition. Immunohistochemical stains showed that the cellular area was positive for S100 and CD34, weakly positive for EMA, negative for Glut-1 and collagen IV, the myxoid area was positive for S100, negative for CD34, strongly positive for EMA and focally positive for Glut-1 and collagen IV. Our results show that congenital melanocytic nevi may show neural differentiation with histopathologic features of hybrid schwannoma/perineurioma.

Wang L ，Wang G ，Gao T 《-》