Spindle cell tumors of the pleura: differential diagnosis
Section snippets
Clinical history and morphology
Clinical data are extremely important in the diagnosis of pleural tumors. Clinical features can help to determine whether the condition is malignant or benign, as well as the origin of the malignancy. For example, when a patient presents with the differential diagnosis of DMM versus CFP, clinical evidence of distant metastases and invasion of the chest wall is diagnostic for malignancy. Instead, a history of pneumonia alerts the pathologist that the lesion may be benign CFP. Age is also an
Histology
Histologically, SMM mimics other spindle cell tumors. In highly cellular tumor areas, pleomorphic spindle cells may grow in a storiform pattern as often seen in malignant fibrous histiocytoma. Other areas may also arrange in herringbone fascicular pattern as seen in soft tissue fibrosarcoma.
Renal cell carcinomas can differentiate into a variety of histological patterns, including spindle cell, making them difficult to distinguish from SMM. Leiomyosarcomas are some of the more commonly occurring
Immunohistochemistry
One single specific marker to identify SMM or other spindle cell tumors of the pleura does not exist. Use of a diverse panel of immunohistochemical markers can lead to a definitive diagnosis when the data are considered collectively and in parallel with the clinical and histological evidence (Table 1). It is problematic to establish a unique immunoprofile for an inherently variable tumor such as MM, i.e., MM can show epithelioid, sarcomatoid, or biphasic characteristics. As a consequence of its
Electron microscopy
MM shares some ultrastructural similarities with adenocarcinoma, such as desmosomal junctions, external lamina, and elongated surface microvilli. Long branching microvilli are diagnostic of MM, whereas adenocarcinomas show short microvilli. Although microvilli are not seen in SMM cells, when these tumors have a small epithelial component, this tumor component should be sampled for EM, and if long branching microvilli are found, they are diagnostic of MM. SS is ultrastructurally defined by
Case 1
A 51-year-old female was hospitalized with a diagnosis of left pleural effusion and pneumonia. Two weeks later, she checked into the hospital again due to difficulty breathing. Radiology revealed a left pleural thickening, and a biopsy was interpreted as DMM. She was given a 6-month prognosis. The patient refused chemotherapy when she learned that chemotherapy usually does not influence the natural course of this disease. She sold her house, retired into a nursing home, and made funeral
Conclusion
The diagnoses of spindle cell tumors of the pleura are challenging because these malignancies show similar clinical presentation, histology, and immunoreactivity. Clinically, they may present with a localized mass or a diffuse pleural thickening. Histology generally shows poorly differentiated and pleomorphic tumors with a variable fibrous component and cellularity. MM is the most common primary tumor of the pleura, and SMM comprises approximately one-third of all MM. However, metastatic
Acknowledgments
This work was partially supported by grants from the Butitta Mesothelioma Foundation, the NCI (IPO1CA114047, RO1CA092657-05, RO1CA106567-02), and the Riviera Country Club (to M.C.).
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2013, Clinics in Chest MedicineCitation Excerpt :Embryologically, they arise from pluripotent stem cells that become neoplastic and diverge into epithelial or sarcomatous components.7 As a class, sarcomas have also been referred to as spindle cell tumors because of their histologic patterns.159 They are quite rare and are often initially mistaken for malignant mesothelioma, metastatic carcinoma, or other nonmalignant processes.10,42,160–167
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2012, ChestCitation Excerpt :The traditional mesothelioma markers calretinin and thrombomodulin each stained 70% of sarcomatoid mesotheliomas, but calretinin was also positive in 17% of sarcomas and in 60% of sarcomatoid carcinomas, whereas thrombomodulin was positive in 38% of sarcomas and 40% of sarcomatoid carcinomas,62 reducing the value of these markers for separating sarcomatoid mesotheliomas from other neoplasms. Other routinely used mesothelial markers, such as CK5/6 and WT-1, are usually negative in sarcomatoid mesotheliomas.62–64 D2-40 shows promise for assisting in differentiating between sarcomatoid mesothelioma and carcinoma; a recent study revealed higher frequencies of staining in sarcomatoid mesotheliomas (86.7%) than in pulmonary sarcomatoid carcinomas (25.9%).65