October Case of the Month

Clinical History: A 59-year-old man was found to have 1.5-cm heterogeneous, non-calcified lung nodule in the left lower lobe on a surveillance CT scan, a year after a right hemicolectomy for a malignant mesothelioma. The nodule was sampled by a transthoracic core needle biopsy and fine-needle aspiration. The biopsy and FNA showed a dense fibrous pseudocapsule surrounding nodules of histiocytoid cells arranged in sheets, whorls, and short fascicles with round normochromatic nuclei, inconspicuous nucleoli, and vacuolated cytoplasm with associated lymphoid aggregates around the nodules (Figures 1 to 6). The neoplastic cells were positive for CD68, focally positive for desmin, and negative for EMA, pancytokeratin, CD21 and calretinin. A diagnostic molecular test was performed.

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