Extranodal follicular dendritic cell sarcoma of the lung.

Follicular dendritic cell sarcoma (FDCS) is a rare, mesenchymal neoplasm that may be nodal or extranodal in location. Lung involvement is rare. It is a slow-growing, painless tumor with a frequent capacity to recur and metastasize. We present a case of extranodal FDCS of the lung with an unusual presentation. A 34-year-old man presented with the complaints of haemoptysis and chest pain. A large left perihilar mass with endobronchial component was found on radiological evaluation. On endobronchial biopsy and mediastinal tru-cut biopsy, differential diagnoses of an inflammatory myo-fibrohistiocytic lesion and leiomyosarcoma were provided on the basis of morphological features of bipolar spindled cells arranged in intersecting fascicles and storiform patterns and immunophenotyping. A pneumonectomy was performed for the mass on which further immunohistochemical evaluation with CD21, CD35, and D2-40 finally helped form a diagnosis of FDCS. The patient recovered well from the surgery and has been on follow-up ever since. Owing to the rarity of this condition and its non-specific clinical features, FDCS is often misdiagnosed in the absence of appropriate immunohistochemistry. An of awareness of its morphological features and immunophenotype is, thus, necessary to provide early treatment and follow-up in order to prevent its recurrence and metastasis.