Alan D. Betensley, M.D. and James R. Yankaskas, M.D.
Division of Pulmonary and Critical Care Medicine, University of North Carolina, Chapel Hill, NC
Introduction: Desmoid tumors, commonly associated with familial adenomatous polyposis (FAP) were first described in 1832. Spontaneous desmoid tumors (not associated with FAP) are quite rare, with an estimated incidence of 2-5 cases per million population per year.1 These tumors lack metastatic potential although they are usually locally aggressive, causing severe morbidity and occasional mortality. Faulkner's series reports that 61% of desmoids arise in the extremities, 18% in the head and neck, 13% in the trunk (including 5% intraabdominal), and 8% are multicentric.2 The following case describes a desmoid tumor presenting as a painful intrathoracic mass.
Case Presentation: A 20 year old white male nonsmoker with a medical history remarkable only for mild asthma and allergic rhinitis presented to the pulmonary clinic with complaints of upper back, chest, and left shoulder pain for 8 weeks. He denied fever, chills, cough, or weight loss. The pain was aggravated by deep inspiration, radiated down the left arm, and was not relieved by physical therapy. On physical examination, he appeared well developed with a weight of 65 kg. Tenderness to palpation was appreciated in the left supraclavicular region, although there was no palpable mass or lymphadenopathy. The cardiopulmonary and abdominal exams were unremarkable. CBC showed a white blood cell count of 5800/mm3, hematocrit 43.1%, and platelets 224,000/mm3. Chest x-ray was remarkable for a large homogenous well circumscribed soft tissue density in the apex of the left hemithorax with apparent pleural involvement. Subsequent CT scan of the chest showed a 6.5 x 5.0 cm homogenous mass located in the left apex and appearing extraparenchymal. There was periosteal reaction involving the left posterior rib adjacent to the mass. There was also apparent involvement of the brachial plexus but no mediastinal or hilar adenopathy. Subsequently, transthoracic percutaneous cutting needle biopsies of the mass were obtained, which revealed mostly noncellular connective tissue with spindle cell proliferation, nonspecific for either a benign or malignant diagnosis. Subsequent biopsies strategically obtained from the junction of skeletal muscle and tumor revealed a bland spindle cell process with mild nuclear pleomorphism, single central nucleoli, and abundant fibrillar background material. In one fragment, skeletal muscle appeared to be infiltrated by this process, consistent with that seen in desmoid tumor.
Discussion: Desmoid tumor usually presents as a slowly enlarging mass with symptoms depending on location. These tumors are defined by well-differentiated intertwining fibroblasts and myofibroblasts arranged in broad bundles and are difficult to distinguish from low grade sarcomas. Fine needle aspirate is usually not adequate for diagnosis due to the lack of cellularity of the tumor, and incisional biopsy is usually recommended. Traditionally, therapy consists of complete surgical excision, although local recurrence rates are high, ranging from 5 to 50% with negative margins and 60-90% after incomplete excision.2 Nonsurgical approaches including radiation and chemotherapy have been attempted for unresectable tumors, especially in cases where wide local excision can be debilitating. Radiation therapy in doses of 50 to 60 Gy have been reported to obtain local control in 62 to 94% of patients treated with a complication rate of 15 to 50 percent.1 In this case, in spite of the intrathoracic nature of the tumor, we were able to avoid thoracotomy and still obtain adequate tissue for histopathologic diagnosis by obtaining a percutaneous transthoracic core needle biopsy at the junction between the tumor mass and normal skeletal muscle. Because surgical excision would have involved left upper extremity amputation due to the brachial plexus involvement of the tumor, we proceeded with radiation therapy. The patient responded and is being followed closely for tumor progression.
Conclusion: Desmoid tumor is rare, but must be considered in the differential of intrathoracic mass. Diagnosis usually requires incisional biopsy, but when necessary it can be made with a well planned percutaneous core needle biopsy. When local invasion precludes resection without significant morbidity to the patient, other modalities such as radiation therapy should be considered.
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