Monoblastic sarcoma, a subtype of myelocytic sarcoma, is an extramedullary manifestation of myelocytic leukemia. We report a case with monoblastic sarcoma involving lung presenting with mediastinal lymhadenopathy, tracheal compression, pleural effusion and superior vena cava (SVC) syndrome which was responsive to chemotherapy.
A 54 year-old white male with hypertension presented with profound dyspnea at rest and non-productive cough. Chest roentogram and computed tomogram (CT) of the thorax showed right pleural effusion with right mediastinal and paratracheal masses. The mediastinal mass was encasing the distal trachea with near complete collapse of the right lung. Thoracentesis revealed an exudative effusion negative for malignant cells. A cervical lymph node biopsy was consistent with monoblastic sarcoma (flow cytometry: MPO-, CD 68+, CD 34-). Bone marrow biopsy was negative for AML. The patient exhibited clinical signs of superior vena cava obstruction and continued to be dyspneic at rest requiring 4 liters of oxygen. Flexible bronchoscopy revealed extensive submucosal disease with extrinsic compression of the tracheobronchial tree. Intravenous steroids to decrease mucosal edema were started, and within one week his room air saturation was 94% on ambulation. Chemotherapy induction with danorubicin, etoposide and Ara-C was initiated. A repeat CT thorax at day 16 demonstrated resolution of the pleural effusion and adenopathy. A repeat bronchoscopy performed 28 days after the initial one showed no extrinsic compression or submucosal disease of the airways. Five months after treatment the patient has had cranial recurrence of disease with cervical adenopathy, but there has been no recurrence of disease in the lung.
Intrathoracic myelocytic sarcoma is rare with only 27 previously reported cases. Of these, 6 were associated with superior vena cava syndrome. Myelocytic sarcoma is further subdivided into granulocytic myeloperoxidase, monoblastic, myelomonoblastic and megakaryoblastic variants. Of the 28 cases 13 patients (46%) responded to treatment and 11 (39%) died. Of the cases with SVC syndrome three survived and three died. The mediastinum was the most common site of involvement (66%) of intrathoracic myelocytic sarcomas. SVC syndrome is an even rarer presentation, seen in only 21% of the cases. This is the first documented case of the monoblastic subtype involving lung. Acute dyspnea in our patient was secondary to pleural effusion, superior vena cava syndrome and tracheobronchial compression by the mediastinal lymphphadenopathy. Thoracentesis assisted in relieving the effusion related dyspnea. It was initially planned to treat the tracheobronchial compression with endobronchial stent placement, but the response to chemotherapy in the intervening period was impressive. A repeat bronchoscopy and CT scan revealed resolution of the tracheobronchial compression and thus stent placement was not deemed necessary. As the SVC syndrome subsided his dyspnea improved. At one week post chemotherapy the patient was off supplemental oxygen. SVC syndrome always portends poor prognosis; except possibly in intrathoracic myelocytic sarcomas in which the response rate to treatment has improved over the years. Pleural effusion in myelocytic sarcoma is distinctly rare and is reported in one other case in addition to ours.
Though the intrathoracic presentation of myelocytic sarcoma is rare, this condition needs to be considered in the differential diagnosis while evaluating patients with mediastinal lymhadenopathy. The quick resolution of the SVC syndrome and extensive tracheobronchial compression highlights the fact that even in cases with significant intrathoracic involvement, early diagnosis and chemotherapy may ultimately improve outcome.
A.d. Corla-Souza, None.