Divergent differentiation, mainly towards various subsets of mesenchymal cells, is encountered sporadically in human malignant peripheral nerve sheath tumours (MPNSTs) but this is the first report of epithelioid components within this neoplasm in a cat. An 8-year-old, spayed female Domestic Shorthaired cat was presented for surgical removal of a subcutaneous mass on the right flank. Morphological and immunohistochemical analysis revealed a malignant neoplasm with spindloid cells intermixed with an epithelioid component that had squamous differentiation. There was intense immunolabelling of vimentin, S100 protein, neuron-specific enolase, laminin and glial fibrillary acidic protein in the spindloid cell component and for cytokeratin (CK) AE1/AE3 and CK5/6 in the epithelial elements. Melanoma-associated antigen, desmin, α-smooth muscle actin, CD18, CD31, ionized calcium binding adapter molecule-1 and CK8/18 were not expressed, which helped differentiate the tumour from other feline spindloid cell neoplasms. These features are characteristic of divergent epithelioid differentiation of MPNST.

Neurofibroma (NF) is a tumour of peripheral nerves, which would be seldom seen in the limbs, particularly in children\'s limbs. Soft, skin-coloured papules or small sub-mucosal nodules appear as these lesions. Neurofibroma is classified into three types: localized, diffuse, and plexiform. The vast majority of nerve injury is sporadic and localized, with an incredibly low risk of tumour formation. Neurofibromatosis can present as multiple skin lesions along with bone deformities in which a full investigation is critical where an undiscovered widespread illness may arise. This case study describes a neurofibroma on the common peroneal nerve of the left lower limb in a 6-year-old child who visited our hospital with chief complaints of pain and swelling around the left proximal leg.

Relapsed rhabdomyosarcoma (RMS) has several therapeutic challenges. The novel treatment for relapsed RMS was surgical management, chemotherapy, and radiotherapy. Reoccurrence significantly occurs in children and adolescents. RMS occurs anywhere in the body but mostly occurs in the legs, head, neck, urinary, and reproductive systems. Here, we present the case of a 19-year-old female who came to the emergency department with complaints of swelling in the left side of the neck that extended toward the face and left eye, breathlessness, and vomiting for one month. She has a history of peripheral nerve sheath tumor and type 1 diabetes mellitus. Surgical management was done through excision of the mesenchymal tumor surgery, and the patient\'s prognosis was good.

Benign Schwannomas are one of the less frequently encountered soft tissue tumours of the hand. We report an interesting case of an 80-year-old gentleman with a painful soft tissue swelling on the radial aspect of his thumb. Ultrasound revealed a well-defined lesion separate from bone and tendon, with mixed echogenicity and moderate internal vascularity. Magnetic resonance imaging demonstrated a 15 × 10 × 23mm lesion with low signal on T1 and high signal on T2. Following surgical excision, histology confirmed benign schwannoma.

OBJECTIVE: Neurofibromatosis type 1 (NF1) is an autosomal dominant tumour predisposition syndrome that can cause plexiform neurofibromas (PNFs). This study examines the surgical procedures that have been performed on large PNFs of the lower extremities.
METHODS: Surgical procedures on the lower extremity performed on 90 patients with NF1 with PNFs were evaluated. The topography of the tumours was classified according to dermatomes and functional units.
RESULTS: A total of 243 surgical interventions on the regions of interest were performed. Neurological complications were rarely noted and usually occurred temporarily. There was no preference for dermatomes affected by PNF. The proportion of patients with malignant peripheral nerve sheath tumours (MPNSTs) in this group was 4/90 (4.4%).
CONCLUSIONS: PNFs often require repeated local interventions to achieve the treatment goal. Local tumour recurrences are to be expected even after extensive tumour reduction. Rapid tumour growth combined with new pain sensations can be signs of a MPNST.

Four cases of a rare melanotic variant of malignant nerve sheath tumour (MNST) in dogs are described. All four cases presented with neurological clinical signs due to multicentric, intradural, intra- and extraparenchymal neoplasms that surrounded the spinal and cranial nerves and infiltrated the adjacent spinal cord and brain. The dogs were young (3 months to 3 years of age), all were female and four different breeds were represented. Characteristic histological features were interweaving fascicles of spindle-shaped cells, sometimes with an architecture reminiscent of Antoni A and B patterns. Some spindle cells showed prominent cytoplasmic melanin pigmentation and such cells were positive by Masson-Fontana stain. Immunohistochemistry performed in three cases was positive for S100 and vimentin, strongly positive for melan A in the melanized cells and negative for glial fibrillary acidic protein and periaxin. Non-melanized cells did not express melan A. Transmission electron microscopy findings in one case were consistent with a peripheral nerve sheath tumour and demonstrated cytoplasmic pre-melanosomes and melanosomes. Melanotic variants of MNSTs are rare in animals with only a solitary report of two previous canine cases in the literature.

UNASSIGNED: Primary orbital schwannoma (POS) is a slow growing, benign encapsulated peripheral nerve sheath tumor that occurs infrequently within the orbit. Recurrence of POS is extremely rare. Previous speculations for reasons of recurrence include incomplete excision and tumor seeding.
UNASSIGNED: We present the fifth case reported in the literature to date of POS that had 2 episodes of recurrences within 8 years after diagnosis, in which rapid and insidious relapses were observed after initial surgical resection. This is also the first reported recurrent POS in which topical Mitomycin-C (MMC) has been employed during surgical excision with an aim to prevent further recurrences.
UNASSIGNED: AND IMPORTANCE: Whilst complete surgical excision remained the standard for management for most POS, when there are multiple recurrences and in cases where total excision is not possible, addition of topical MMC may be an option that may bring about tumour regression as demonstrated in our case.

We report the pathological features of a facial squamous cell carcinoma (SCC) and an abdominal peripheral nerve sheath tumour (PNST) with rhabdomyoblastic differentiation in an aged free-ranging rough-toothed dolphin (Steno bredanensis). The animal was found stranded dead in poor body condition. On external examination, there was a 25 × 7 × 3 cm extensively ulcerated area on the right maxillary region of the rostrum, involving the oral mucocutaneous junction with prominent nodular edges, severe soft tissue loss and extensive maxillary and premaxillary bone lysis. On abdominal dissection, a 5 × 4 × 3.5 cm pale tan to red, raised mass expanded the inner aspect of the right transverse abdominis muscle. Microscopically, the aggressive facial lesion was an acantholytic SCC with extensive osteolysis; there was no evidence of metastasis in the tissues examined. The abdominal mass had cytohistomorphological features compatible with a localized PNST, including whorling, Antoni A and Antoni B areas and Verocay bodies intermixed with rhabdomyoblastic components, as suggested by phosphotungstic acid haematoxylin stain. This neoplasm was locally infiltrative, yet no metastases were observed in the tissues examined. No immunohistochemical investigations could be performed due to lack of tissue availability. Total DNA from the formalin-fixed and paraffin wax-embedded SCC was extracted and tested by polymerase chain reaction for herpesvirus and papillomavirus genetic material. There was no amplification for either of these genera. Other pathological findings observed in this animal were related to the \'live-stranding stress response\'. The severity and extent of the facial SCC likely related to anorexia and poor body condition and might have played a role in the stranding and death of this dolphin. These two tumour subtypes add to the relatively uncommon reports of neoplasia in cetaceans. Specifically, these appear to be the first neoplasia records for rough-toothed dolphins, including the first documentation of a PNST with features compatible with rhabdomyoblastic differentiation in a marine mammal.

A 15-year-old neutered male miniature pinscher was presented with a pedunculated mass (4 × 1 cm) in its urinary bladder. Exploratory cystotomy revealed that the mass was located at the trigone of the bladder and projected into the lumen. The cut surface of the mass was homogeneous grey to tan in colour with focal brown pigmentation. Microscopically, the mass was predominantly composed of neoplastic spindle cells characterized by moderate cellular pleomorphism, invasion into the muscular layer of the bladder wall and few mitotic figures. The neoplastic spindle cells formed interwoven bundles intersecting at various angles. Immunohistochemically, these cells were negative for cytokeratin 7 and α-smooth muscle actin, but strongly expressed S100 and vimentin, confirming a diagnosis of a malignant peripheral nerve sheath tumour (PNST). To the best of our knowledge, this is the first report of a primary malignant PNST in the urinary bladder of a dog.

Subcutaneous spindle cell tumours characterized by whorling growth patterns are common in dogs and are identified as a distinct entity. These tumours were misnamed as hemangiopericytomas (HPCs) because of some minor morphological parallels with their human counterparts. In veterinary medicine, the cell of origin of HPC has been under debate for a long time. Some authors have suggested a perivascular origin while others a perineural one. The evidence of the orientation of the neoplastic cells around the vessels and the expression of contractile proteins supported a perivascular origin while S100 expression and an inconsistent vascular connection supported a perineural origin. Despite the morphological similarities with peripheral nerve sheath tumours in humans, the perineural origin was supported mainly by the expression of markers with low specificity. On the contrary, the majority of studies have supported the perivascular origin of \'old\' canine HPC. Since a variable degree of myoid-pericytic differentiation was described, the term perivascular wall tumours (PWTs) were suggested to substitute HPC. Once the diagnostic criteria of PWTs were defined, the clinical behaviour and prognostic variables were investigated, demonstrating differences as compared with the group of canine soft tissue sarcomas (STSs) in general. PWTs are less aggressive, mostly locally invasive, and rarely metastasizing. Their behaviour seems to be less influenced by histological grade, suggesting that canine STSs are heterogeneous. The study of the biological behaviour of specific STS tumour types may be valuable in detecting differences which have passed unnoticed when STSs have been studied concomitantly.