Differentiation Between Pleuropulmonary Desmoid Tumors and Solitary Fibrous Tumors: Role of Histology and Immunohistochemistry

Pleuropulmonary desmoid tumors (DTs) are extremely rare tumors that can histologically resemble other neoplasms more common to the lungs and pleura. Differentiating between desmoid tumors and solitary fibrous tumors (SFTs) can be particularly difficult. Other entities that may also be considered in the differential diagnosis include desmoplastic malignant mesothelioma, fibrosarcoma and variants, other spindle cell sarcomas, inflammatory myofibroblastic tumor, schwannoma, scar, and the capsule surrounding another process. Although the clinical and radiographic presentations of DTs and SFTs differ somewhat, and therefore clinical information can favor one diagnosis or the other, ultimately histological distinction is crucial.

Intrathoracic desmoid tumors typically arise in the chest wall and can protrude or extend into the pleural cavity secondarily. Rare cases, however, have been described that appear to represent true primary pleural or pulmonary neoplasms (Winer-Muram et al., 1994; Wilson et al., 1999; Iqbal et al., 2001; Andino et al., 2006). SFTs, on the other hand, have been reported in most organ systems, but most commonly arise in the pleura, forming well-circumscribed and sometimes polypoid or pedunculated pleural-based masses. Although defined histopathologic criteria exist to separate these tumors microscopically, these features may not be apparent in small or less representative samples. Fortunately, as reviewed by Andino et al. (2006) and Wilson et al. (1999), immunohistochemistry can aid in the distinction between primary pleuropulmonary DTs and SFTs, while also providing insight into the pathogenesis of these unusual neoplasms.