Plexiform pattern in cutaneous granular cell tumors

Granular Cell Tumor in a Horse: Multifocal Pulmonary Distribution and Evidence of Autophagy in Tumorigenesis

Granular cell tumor (GCT) is a soft tissue neoplasm characterized by abundant intracellular eosinophilic granules. The majority of GCTs are benign, although some display malignant behavior. Furthermore, GCTs may mimic other neoplasms. The clinical course and biology of GCTs are poorly understood. Regarding the histogenesis of GCT, a Schwann cell origin is currently favored in light of immunohistochemical and ultrastructural analyses. However, based on literature data, some of the primitive GCTs show non-neural origin; therefore, the histogenesis of this tumor has remained enigmatic. Granular cell tumors can arise in almost any location of the body and typically present as solitary lesions. This study illustrates equine primary GCT with multifocal pulmonary distribution. The presence of GCT in the respiratory tract becomes a diagnostic challenge on initial presentation. The morphologic details of this case are presented. Immunohistochemical evaluation confirmed the neuronal origin of equine GCT and the relation of intracytoplasmic granules formation to an autophagy phenomenon. Most of the discussion is related to GCT nature to help characterize molecular aspects associated with the biological behavior of this tumor and its heterogeneity.

Dermal and Subcutaneous Plexiform Soft Tissue Neoplasms

This article presents an overview of soft tissue tumors that have a plexiform histomorphology. The more commonly encountered entities, including plexiform fibrohistiocytic tumor, cellular neurothekeoma, dermal nerve sheath myxoma, plexiform schwannoma, and plexiform neurofibroma, are discussed in detail, and other tumors are noted. Information on clinical features, microscopic findings, ancillary studies, differential diagnosis, and prognosis is provided for each entity.

Oral plexiform schwannoma with unusual epithelial induction

Rare epithelial structures in benign nerve sheath tumors are almost always glandular in appearance. We describe a case of intraoral plexiform schwannoma with concurrent squamous epithelial hyperplasia. The lesion occurred as a pigmented nodule on the gingiva of a 35-year-old woman with no systemic involvement. Histologically, unencapsulated, plexiform fascicular proliferations of schwann cells could be traced from the submucosa to the lamina propria, finally making direct contact with heavily pigmented, elongated rete ridges of the overlying epithelium. Also noted was a schwannian network centered on clustered odontogenic epithelial rests of mature squamous-type, the number and size of which had markedly increased. Impressive immunoprofiles of periepithelial neural microfascicles included the complete absence of axon and perineurium and the unexpected presence of endoneurial fibroblasts. The repertoire of epithelial changes was in a confined area with no extension beyond, supporting hyperplasia induction by an underlying/surrounding schwannoma.

Neurogenic tumors of soft tissue

Neurogenic tumors are an uncommon yet important category of soft tissue tumors in children and adolescents because of their frequent association with various genetic syndromes. The heterogeneous cellular composition of the peripheral nerve and the wide metaplastic capacity of the neural crest and its derivatives generate a variety of neoplasms with neurogenic differentiation. This article reviews the clinicopathologic features and differential diagnosis of neurogenic tumors in the first two decades of life, and highlights use of selected ancillary methods for diagnosis.

Pathology of peripheral nerve sheath tumors: diagnostic overview and update on selected diagnostic problems

Peripheral nerve sheath tumors are common neoplasms, with classic identifiable features, but on occasion, they are diagnostically challenging. Although well-defined subtypes of peripheral nerve sheath tumors were described early in the history of surgical pathology, controversies regarding the classification and grading of these tumors persist. Advances in molecular biology have provided new insights into the nature of the various peripheral nerve sheath tumors, and have begun to suggest novel targeted therapeutic approaches. In this review, we discuss current concepts and problematic areas in the pathology of peripheral nerve sheath tumors. Diagnostic criteria and differential diagnosis for the major categories of nerve sheath tumors are proposed, including neurofibroma, schwannoma, and perineurioma. Diagnostically challenging variants, including plexiform, cellular and melanotic schwannomas are highlighted. A subset of these affects the childhood population, and has historically been interpreted as malignant, although current evidence and outcome data suggest they represent benign entities. The growing current literature and the author's experience with difficult to classify borderline or "hybrid tumors" are discussed and illustrated. Some of these classification gray zones occur with frequency in the gastrointestinal tract, an anatomical compartment that must always be entertained when examining these neoplasms. Other growing recent areas of interest include the heterogeneous group of pseudoneoplastic lesions involving peripheral nerve composed of mature adipose tissue and/or skeletal muscle, such as the enigmatic neuromuscular choristoma. Malignant peripheral nerve sheath tumors (MPNST) represent a diagnostically controversial group; difficulties in grading and guidelines to separate "atypical neurofibroma" from MPNST are provided. There is an increasing literature of MPNST mimics which neuropathologists must be aware of, including synovial sarcoma and ossifying fibromyxoid tumor. Finally, we discuss entities that are lacking from the section on cranial and paraspinal nerves in the current WHO classification, and that may warrant inclusion in future classifications. In summary, although the diagnosis and classification of most conventional peripheral nerve sheath tumors are relatively straightforward for the experienced observer, yet borderline and difficult-to-classify neoplasms continue to be problematic. In the current review, we attempt to provide some useful guidelines for the surgical neuropathologist to help navigate these persistent, challenging problems.

Lesions of the skin and superficial tissue at breast MR imaging

Although numerous studies have outlined the benefits of contrast material-enhanced magnetic resonance (MR) imaging for the detection of breast parenchymal findings, the assessment of lesions of the skin and superficial tissue at breast MR imaging has largely been overlooked. Such lesions, both benign and malignant, are commonly encountered at breast MR imaging, and their detection and diagnosis are often imperative. These lesions include superficial, locally extensive, inflammatory, and recurrent breast cancers; iatrogenic changes; sebaceous cysts; and less prevalent diseases such as granulomatous mastitis and angiosarcomas, among others. As MR imaging continues to be used with increasing frequency in both the screening and diagnostic settings, these lesions will be encountered more often; consequently, a better understanding of which lesions may be ignored and which require further evaluation will become increasingly important. Frequently, MR imaging alone may not clearly indicate the cause of lesions of the breast skin and superficial tissue. However, radiologists should thoroughly assess such lesions, taking into consideration the spectrum of possible causes. Mammography, ultrasonography, consultation with clinicians or dermatologists regarding physical examination findings, and, when necessary, correlation with pathologic findings in biopsy specimens may be used in conjunction with MR imaging to establish both the importance of these lesions and their definitive diagnoses.