Schwannoma with focal smooth muscle differentiation: a potential pitfall in the interpretation of core biopsies

Schwannoma of the Breast: A Case Report and Review of the Literature

Schwannoma arising within breast parenchyma is very rare. This report describes such a case in a 58-year-old woman. The tumor, which measured 4.4 × 3.5 × 2.1 cm, was painless, mobile and elastic-soft. Mammography showed a well-circumscribed, oval-shaped nodule without microcalcifications. At ultrasonography it appeared as a hypoechoic solid mass. Fine-needle cytology revealed several clusters of spindle cells indicative of a neoplasm of mesenchymal origin. Histological examination evidenced the characteristic morphological appearance of a schwannoma with Antoni A and Antoni B areas. A review of the 23 proven cases of breast schwannoma is included. The main differential diagnostic findings are also discussed.

From the radiologic pathology archives: diseases of the male breast: radiologic-pathologic correlation

Male breast disease includes a variety of benign and malignant conditions, many of which are hormonally influenced. Gynecomastia and skin lesions account for the majority of conditions in symptomatic men with a palpable abnormality, and these conditions should be accurately recognized. Imaging patterns of gynecomastia include nodular, dendritic, and diffuse patterns. Histopathologically, the nodular and dendritic patterns correlate with the florid and quiescent (fibrotic) phases of gynecomastia, respectively. The diffuse pattern may have features of both phases and is associated with exposure to exogenous estrogen. Benign-appearing palpable masses in male patients should be approached cautiously, given the overlapping morphologic features of benign and malignant tumors. In addition to gynecomastia, other benign male breast tumors include lipoma, pseudoangiomatous stromal hyperplasia, granular cell tumor, fibromatosis, myofibroblastoma, schwannoma, and hemangioma. Male breast cancer accounts for 1% of all breast carcinomas. Invasive ductal carcinoma accounts for the majority of cases in adult males and typically appears as a subareolar mass without calcifications that is eccentric to the nipple. Other epithelial and mesenchymal tumors that may occur, albeit not as commonly as in women, include papillary carcinoma, invasive lobular carcinoma, adenoid cystic carcinoma, liposarcoma, dermatofibrosarcoma, pleomorphic hyalinizing angiectatic tumor, basal cell carcinoma of the nipple, hematopoietic malignancies, and secondary tumors. Knowledge of the natural history, clinical characteristics, and imaging features of tumors that occur in the male breast will help narrow the radiologic differential diagnosis and optimize treatment.

Recurrent retroperitoneal Schwannomas displaying different differentiation from primary tumor: case report and literature review

Background

Retroperitoneal Schwannomas are uncommonly found in the retroperitoneum and few of them show malignant transformation and invasion. Local recurrence are common in malignant Schwannomas with very few reports of tumor distinct differentiation at recurrences.

Case presentation

We report here a rare case of retroperitoneal schwannoma with multiple origins from retroperitoneum and pelvic wall. Pathological examination confirmed the case as a schwannoma with malignant transformation. Radical dissection of the tumors along with the sacrifice of adjacent sigmoid colon and left kidney failed to provide a cure for this patient. Due to tumor recurrence, a second and a third surgery of radical excision were performed 6 months and 17 months later after the first surgery, respectively. Histopathologic analysis identified that the recurrent tumors were different from the original schwannoma because of their smooth muscle-like differentiation.

Conclusion

Malignant schwannomas are uncommon sarcomas with a high incidence of local recurrence. Distinct immunohistochemical staining results of the tumors at recurrence indicate their potential of smooth-muscle like differentiation. Radical excision of the tumors may provide benefit for their local recurrences.

Actin expression in neural crest cell-derived tumors including schwannomas, malignant peripheral nerve sheath tumors, neurofibromas and melanocytic tumors

Tumors that originate from neural crest-derived cells represent a heterogeneous group of neoplasms including benign and malignant tumors with melanocytic and schwannian differentiation. The immunophenotype of these tumors is well known but little is known about the expression of smooth muscle/myofibroblastic markers in these tumors. A total of 590 neural crest-derived tumors (50 benign schwannomas, five malignant peripheral nerve sheath tumors, 80 neurofibromas, 240 nevocytic nevi, 115 primary melanomas, and 100 melanoma metastases) were studied with respect to alpha-smooth muscle actin and muscle-specific actin expression. alpha-Smooth muscle actin and muscle-specific actin-positive tumor cells with a co-expression of S-100 protein were found in one benign schwannoma, one primary cutaneous melanoma, and four melanoma metastases. Four of these cases were examined ultrastructurally, but typical actin filaments with focal densities were not found in any of the four. Other immunohistochemical markers examined including desmin, h-caldesmon and smooth muscle myosin heavy chain were negative in the tumor cells. The present results suggest that neural crest-derived tumors could show expression of alpha-smooth muscle actin on rare occasion.

Coexistence of different tissue tumourigenesis in an N-methyl-N-nitrosourea-induced mammary carcinoma model: a histopathological report in Sprague-Dawley rats

N-methyl- N-nitrosourea (MNU), a highly potent carginogen, is widely used to generate mammary tumours in murine species. In a model of MNU-induced mammary carcinogenesis using immature female Sprague-Dawley rats, large mammary tumours (largest dimension ≥0.5 cm) were obtained within a very short period of time. In addition, in the rats bearing MNU-induced mammary carcinomas, there were a number of tumours whose origins were not from mammary tissue but from several different tissues and from mammary non-epithelial tissue. The tumours were of mesenchymal or epithelial origin and they were located in the inguinal region. These tumours were diagnosed as fibroadenoma, combined tubular adenoma and fibroadenoma, hyperkeratotic papilloma, keratinous cyst and malignant peripheral nerve sheath tumour (MPNST) with smooth muscle differentiation. The occurrence of these other tumours in addition to the development of the mammary carcinomas may be attributed to a direct local effect of the intraperitoneal administration of MNU during the sexual development of the immature rats. In the MNU-induced mammary tumour model, coexistence of tumourigenesis in various non-mammary tissues should be considered an important factor that may interfere with experimental procedures and results and also the quality of life of the tumour-bearing animals.

Divergent myoid, neuroendocrine, and perineural differentiation in a nasal tumor of a patient with Carney complex

A 39-year-old woman with Carney complex presented with a stroke of undetermined etiology. Computed tomography showed bilateral thalamic infarctions and also an unsuspected multicompartmental cystic neoplasm that had eroded the anterior clivus and extended forward into the nasopharynx. Histologically, the mass appeared benign and was composed of spindle cells and multiple foci of striated muscle. Immunohistochemically, the spindle cells were strongly reactive for S-100 protein and to a lesser extent for CD57, collagen IV, neuron-specific enolase, smooth muscle actin, epithelial membrane antigen, and glut-1. The striated muscle cells were positive for desmin and myogenin. The MIB-1 labeling index was 0.5%. Ultrastructural examination was necessary to reveal the full extent of divergent differentiation. Ultrastructurally, the spindle cells showed divergent differentiation along several cell lines, including smooth muscle, neuroendocrine, hybrid smooth muscle-neuroendocrine, perineural-like cells, and striated muscle. The occurrence of this unique lesion in a patient with the Carney complex raises the possibility that it may be a rare component of the syndrome.

Malignant peripheral nerve sheath tumour (malignant schwannoma) in the diaphragm of a goat

This report describes a malignant schwannoma in the diaphragm of a 2-year-old goat. The immunohistochemical and histological features indicated a diagnosis of malignant schwannoma rather than neurofibrosarcoma. The diaphragm represents an unusual location for neoplasia in both domestic animals and human beings. A possible anatomical origin from the phrenic nerve is discussed.

Low grade malignant peripheral nerve sheath tumor with smooth muscle differentiation

Malignant peripheral nerve sheath tumors are usually Schwann cell derived. Differentiation along mesenchymal lines is uncommon. Herein we present an example with smooth muscle differentiation occurring in the left distal forearm of a 62-year-old male with neurofibromatosis type I. Incisional biopsy of the slowly growing mass demonstrated a low-grade malignant peripheral nerve sheath tumor with strong S-100 protein immunoexpression as well as focal smooth muscle actin staining in atypical neoplastic cells. Immunostains for epithelial membrane antigen, neurofilament protein, glial fibrillary acidic protein, CD57, desmin, and myogenin were negative. The MIB-1 labeling index was 5.4%. Electron microscopy revealed arrays of microfilaments (actin myofilaments) variably associated with fusiform dense bodies, plasmalemmal micropinocytotic vesicles, and foci of external lamina (basement membrane) consistent with smooth muscle differentiation. Smooth muscle should be added to the spectrum of differentiation exhibited by malignant peripheral nerve sheath tumors. Its recognition requires exclusion of the alternative diagnosis of leiomyosarcoma.