We report a case of a desmoid tumor or a desmoplastic fibroma, an extremely rare benign bone tumor that presented as a pleural based density radiologically.
A 61-year-old African American male presented with left-sided sharp chest pain for a month. Chest radiography and chest Computerized Axial Tomography Scan showed a 3x2 cm pleural based density in the posterior aspect of the left upper lobe (Fig 1). Adjacent rib showed bone destruction with thin sclerotic rims. Bone imaging with Technetium 99m-HDP showed increased focal uptake in the region of 5th rib adjacent the tumor. Video-assisted thoracoscopic surgery was performed but the firm consistency of the mass made frozen section technically impossible. The patient underwent thoracotomy and the lesion was excised totally with posterior segments of the 3rd, 4th and 5th ribs. Histological examination showed sheets of spindle cells partially encircling the bone and focally involving extensive areas of cortical and medullary bone (Fig 2&3). Cells showed moderate amount of hyperchromaticity without high-grade anaplasia or atypical mitotic figures. Immunohistochemical staining showed scattered areas of positivity with smooth muscle actin and desmin 33. Staining for S-100 and CD34 was equivocal. Tumor extended very near but without involvement of the pleura. Resection margins were free of tumor. Post-operatively patient developed acute renal failure requiring hemodialysis for uremic encephalopathy that eventually resolved. Patient was discharged on post-operative 27th day still complaining of mild intermittent chest pain.
Desmoid tumors are benign but locally aggressive myofibroblastic neoplasms originating from the muscle aponeurosis or fascia constituting 3% of all soft tissue tumors. They are primarily located on abdominal wall. Extra-abdominal sites include shoulder (20%), chest wall and back (15%), thigh (12%), mesentery (10%), neck (10%), and knee (7%). Desmoid tumors are composed of abundant collagen surrounding poorly circumscribed dense bundles of eosinophilic spindle cells with regular nuclei, pale cytoplasm and absence of mitoses. Tumor cells can be reactive for vimentin, desmin, and smooth muscle actin. Radiographs may show a non-specific soft-tissue mass and underlying bone involvement in 6-37% of patients. Bone scintigraphy usually demonstrates increased uptake on blood pool and static images in areas adjacent the tumor. Desmoplastic fibroma, which is considered as the bone counterpart of desmoid tumor, is a very rare primary tumor of bone with a reported incidence of 0.06% of all bone tumors. First described by Jaffe in 1958, it is most commonly found in the long tubular bones (56%), mandible (26%), and pelvis (14%). Histologically similar to desmoid tumor, it shows prominent bundles of fibrous tissue composed of slim spindle shaped fibroblasts without mitoses or atypical cells, and variable amounts of bonds of collagen fibers. Radiologically, tumors are expansile lytic lesions often with internal trabeculation (91%) and soap bubble appearance. Desmoplastic fibroma in the rib is extremely rare, with only four cases reported in the literature up to date. In our case, thoracic wall mass that first appeared to be pleural in origin resembles to both desmoid tumor and desmoplastic fibroma histologically, although the radiological features favor desmoid tumor. Management does not differ in both entities and consists of wide local resection. Local recurrence is a definite possibility and metastatic potential is negligible.
In this case, the lesion, which presented as a pleural based density, was likely a desmoid tumor although its bone counterpart, desmoplastic fibroma, could not be ruled out.
Theophilus Ogungbamigbe, None.