2. A rare primary lung MPNST exhibiting peculiar ‘small cell’ features diagnosed through fna with tissue correlation

Abstract

Background We report a case of primary intraparenchymal lung malignant peripheral nerve sheath tumour (MPNST) originally diagnosed through fine needle aspiration biopsy (FNAB) incidentally presenting with a peculiar feature in an adult female without NF-1. Aim To present, document and describe the cytomorphological features and tissue correlation of a case of primary lung MPNST with ‘small cell’ features. Case history The patient was an adult female with hemoptysis. CT scan revealed a left lower lobe mass. CT-guided FNAB was performed and MPNST was considered. One month later, she was eventually admitted for dyspnoea. She was subsequently scheduled for thoracotomy with frozen section. Wedge biopsy was done and submitted for histopathological examination. Results FNA cytology showed loose clusters atypical epithelioid cells and spindle cells as singles. The cellblock revealed interlacing fascicles of spindle cells with plump hyperchromatic nuclei and tapered cytoplasm. Some fragments showed epithelioid cells with rosette-like formation. Epithelioid and spindle cells were negative for cytokeratin, desmin and SMA. NSE was positive in >50% of the tumour cells. Frozen section diagnosis favoured small cell carcinoma. The mass appeared hypercellular in the preserved areas and was composed of epithelioid to spindle-shaped cells. Extensive areas of necrosis were noted. Mitotic count was high at 8–12 per 10 HPF. The lesional cells showed positivity against vimentin and weak focal positivity against S-100, while synatophysin, SMA, desmin and TTF-I all showed negative reactions. Conclusion We have documented and described a case of primary MPNST of the lung in an adult female without NF-1 with peculiar ‘small cell’ features. With careful attention to the cytomorpholo-gical details of MPNST, it could be confidently considered through FNA with the aid of immunohistochemistry.