
Unveiling the Cytological Enigma of Malignant Spindle Cell Neoplasm of Peripheral Nerve Sheath: A Clinicopathological Image
EJ01-EJ03
Correspondence
Dr. Shreya Giri Goswami,
Junior Resident, Department of Pathology, Datta Meghe Institute of Higher Education and Research, Wardha, Maharashtra, India.
E-mail: shreya18g@gmail.com
Peripheral Nerve Sheath (PNS) tumours are rare neoplasms arising from deeper soft tissues, peripheral nerves, perineural cells, or Schwann cells with ectomesenchymal origins (1). The incidence rate is between 4-13%, with the upper extremity being the most commonly involved site (45%) (2). The role of Fine Needle Aspiration Cytology (FNAC), based on the cytomorphology of these neoplasms of the PNS, is challenging and often confusing, underscoring the complex diagnostic nature of the lesions. Therefore, FNAC details were highlighted by presenting a clinicopathological image and providing insight into the intricate cytomorphology involved.
A 55-year-old woman presented to the surgery outpatient department with complaints of swelling near the elbow joint of her left forearm, accompanied by dull, aching pain for one year (Table/Fig 1). The swelling was initially small, but over 10 months, it gradually increased to its current size. There was no history of locoregional trauma or falls. Upon locoregional examination, a 5×4 cm nodular swelling was observed, which was firm, fixed and tender, with surface ulceration of the skin present on the extensor aspect of the forearm, distal to the left elbow joint. There was no local temperature rise or involvement of the ulnohumeral joint. The general examination did not reveal any swelling at other sites. She did not provide any history of prior surgeries. The levels of electrolytes were within normal limits, and the serum urea and creatinine levels indicated normal kidney function.
The patient underwent ultrasonography (USG) of the left forearm, which showed a well-defined, heterogeneously hyperechoic lesion in the subcutaneous plane. There was no evidence of bony involvement and a radiodiagnosis of a soft-tissue tumour was given. Resonance Imaging (MRI) revealed a well-defined ovoid mass in the subcutaneous plane. The lesion was heterogeneously hyperintense with areas of central necrosis (Table/Fig 2). The differential diagnosis included fibrosarcoma, dermatofibrosarcoma protuberans, poorly differentiated carcinoma, malignant fibrous histiocytoma nerve sheath tumour, along with the need for FNAC correlation. FNAC was carried out under USG guidance. The smears were of high cellularity, revealing multiple fragments of spindle nuclear cells (Table/Fig 3). A few fragments showed peripheral nuclear palisading and attempted whorling. In some areas, the cell borders exhibited feathery margins (Table/Fig 4). These elongated spindle nuclei showed moderate pleomorphism and were hyperchromatic. A few cells demonstrated bipolar blunting of nuclei and prominent nucleomegaly with uneven chromatin (Table/Fig 5). The cytoplasm of these cells appeared to merge with intracellular hyalines. There were also a few spindle bare nuclei with atypia and infrequent mitosis in the background. The diagnosis of malignant spindle cell neoplasm of peripheral nerve sheath tumour (MPNST) was offered.
Following the cytodiagnosis, the patient underwent surgical resection of the tumour (Table/Fig 6). The histopathology revealed pleomorphic spindle cells arranged in a fascicular arrangement. These cells exhibited scant wavy cytoplasm with marked anisonucleosis and a high N/C ratio. The hyperchromatic nuclei contained loose open chromatin, with nucleoli present in some.
Mitotic figures were also observed. The histopathological features were suggestive of a malignant mesenchymal tumour (Table/Fig 7). Immunohistochemical analysis confirmed the diagnosis of MPNST, showing diffuse positive immunoexpression for S-100 (Table/Fig 8) and SOX-10. The patient was followed-up by the Institute’s tumour board committee and was initiated on postoperative radiotherapy and chemotherapeutic drugs such as doxorubicin and ifosfamide as part of the adjunctive treatment plan.