Solitary fibrous tumours (SFTs) are soft tissue tumours of fibroblastic origin. 1 These tumours were first reported in pleura but are also detected at extra-pleural locations. 2,3 The underlying genetic pathology is a paracentric inversion in chromosome 12q, leading to NAB2-STAT6 gene fusion, which further activates several growth factor pathways. 1,2,4 Morphologically, these tumours are composed of spindle-shaped cells along with prominent, dilated and branching blood vessels, described as "staghorn vasculature". 5

Background: Epidermal growth factor receptor (EGFR)tyrosine kinase inhibitor (TKI) resistance may be acquired via genotypic and/or phenotypic transformations. Herein, we report an extremely uncommon case with sequential small cell transformation and EGFR T790M mutation, in an elderly female with EGFR exon 21 L858R-mutant lung adenocarcinoma, following treatment with a first-generation EGFR-TKI.Case: A 67-year-old female never-smoker presented with a cough and dyspnoea of 2 months' duration. Computerised tomography revealed a 39 mm lesion in the upper lobe of the right lung with pleural effusion. Pleural fluid cytology revealed metastatic lung adenocarcinoma, and EGFR testing revealed exon 21 L858R mutation. She was started on gefitinib. After a progression-free survival of 31 months, she presented with disease progression and multiple extra-thoracic metastases. Fine needle aspiration cytology of a chest wall lesion revealed metastatic small cell carcinoma. EGFR testing on this aspirate revealed persistent L858R mutation only. In view of small cell transformation, chemotherapy (etoposide and carboplatin) was administered. After 4 months, ascitic fluid cytology revealed metastatic adenocarcinoma with persistent L858R mutation and an acquired T790M mutation (both detected on liquid biopsy as well) indicating amplification of the adenocarcinoma clone and regression of the small cell carcinoma clone. She was then initiated on osimertinib. Conclusions:The index case highlights the significance of serial EGFR genotyping along with repeated tissue and/or blood sampling in the prompt detection of genetic and phenotypic resistance mechanisms to EGFR-TKIs. Furthermore, it lends evidence in support of the upfront treatment approaches targeting the heterogeneity of acquired EGFR-TKI resistance mechanisms.

Giant cell tumour (GCT), also known as osteoclastoma, is an osteolytic tumour. It involves the epiphyseal and metaphyseal regions of long bones in adults. On rare occasions, these may occur in paediatric patients, and may involve uncommon locations such as the sternum, pelvis and, particularly infrequently, rib bones. We present a rare case of GCT in the rib of a child, diagnosed on fine needle aspiration.

Introduction: Giant Cell Tumour of Tendon Sheath (GCTTS), also known as localised nodular tenosynovitis, is a slow growing benign soft tissue tumour arising from synovium of tendon sheath, bursa or joint. Clinically, the lesions occur as skin-coloured nodules typically on the extremities. These tumours occur more frequently on the upper limbs especially hands (77%) where they form the second most common tumour following simple ganglion cyst. Aim: To describe the cytomorphologic findings in GCTTS and their histopathological features. Materials and Methods: This retrospective study was conducted at Department of Pathology, ESI Hospital, Delhi, India, in 12 diagnosed GCTTS cases for their cytological features from January 2015 to December 2017. Fine Needle Aspiration Cytology (FNAC) was performed with a 22-gauge needle attached to a 10 mL syringe. Smears were air-dried and stained with Giemsa stain. Cytomorphology of all the selected cases were analysed and descriptive statistics were used to evaluate the cases. Results: A total of 12 cases of GCTTS were retrieved. Diagnosis of GCTTS was made by FNAC in all the cases and confirmed by histopathological examination in half of the cases. The mean age of presentation was 39 years. Of these, 8 (66.67%) were women and 4 (33.33%) were men. The lesions were found most commonly over the index finger (n=5) followed by the ring finger (n=3), thumb (n=2), middle finger (n=1) and little finger (n=1). The most frequent clinical presentation was a painless, nodular, slow growing firm swelling over the finger. FNAC revealed cellular smears with few clusters and numerous scattered stromal cells along with interspersed multinucleated giant cells. Conclusion: A definitive preoperative diagnosis of GCTTS obtained through FNAC helps in formulating appropriate treatment plan. Histopathologic examination will confirm the cytological diagnosis and can help to predict recurrence by providing information on the resection margin, any satellite nodules, variable cell types and mitotic activity.

Lung carcinoma is the most common malignancy worldwide. 1 Pulmonary blastoma (PB) is a rare lung cancer constituting approximately 0.25%-0.5% of all pulmonary neoplasms. 2 The risk of occurrence is similar in males and females, with a peak incidence in the fourth to fifth decades of life. 3 PB is an aggressive tumour known for distant metastasis and recurrence. The tumour displays a biphasic morphology with an admixture of epithelial and primitive stromal components. It is a peculiar entity, particularly regarding terminology, and is categorised under sarcomatoid carcinoma of the lung.Foetal adenocarcinoma (FA) of the lung, earlier considered a variant of PB, is now placed under adenocarcinoma and is epithelial only.Both PB and low-grade FA are frequently driven by mutations in the catenin beta 1 (CTNNB1) gene, causing activation of the Wnt pathway via aberrant nuclear/cytoplasmic localisation of beta-catenin (β-catenin). PB does not share this mutational profile and is a purely mesenchymal tumour.Whilst the histopathological features of PB have been described well in the literature, published data on cytomorphology is scarse. [4][5][6] We herein describe a case of a 59-year-old female who presented with scalp swelling. The patient was operated on for a lung tumour reported as PB on histopathology. Fine needle aspiration cytology (FNAC) was done from the scalp swelling. Cytomorphology supplemented with immunocytochemistry (ICC) on cell block confirmed the diagnosis of a metastatic PB. | C A S E REP ORTA 59-year-old female presented in the month of June 2021 with a chief complaint of haemoptysis for the past 3 months.