Talc crystals in pleurodesis-associated talc granuloma

摘要

A 67-year-old man with malignant melanoma was found to have a right-sided hyperdense, pleural-based mass worrisome for recurrent malignancy on CT scan. The lesion was associated with increased fiudeoxyglucose (FDG) uptake on positron emission tomography (PET)-CT scan. Five years earlier, he had been diagnosed with malignant melanoma of the cheek, which had metasta-sized to the lung and brain. He subsequently developed right pleural effusion secondary to Dasatinib therapy and underwent thoracoscopic talc pleurodesis, with eventual resolution of the effusion. Fine-needle aspiration and core biopsy of the right pleural-based plaque was performed. On-site evaluation with rapid Romanowsky (Diff-Quik~R)-stained smears showed numerous plasma-cytoid cells with abundant finely vacuolated cytoplasm and round to ovoid nuclei with indistinct nucleoli, bearing a superficial resemblance to melanoma cells. Also noted were lymphocytes and rare giant cells. Although numerous crystals and aggregates of crystals were also present in the smears, they were optically clear and not readily recognizable during the on-site evaluation. Furthermore, the presence of numerous plasmacytoid cells, some showing intracytoplasmic pigment, raised the supsicion of metastatic melanoma. Needle core biopsies were obtained, and H&E-stained sections showed a marked foreign-body-type reaction to flat, needle-shaped or sheet-like crystals ranging in size from 5 to 30 um in length (Fig. C-l). Immunohistochemistry preformed on the cell blockeedle-core sections revealed that the