Ectopic hematopoietic activity outside the marrow is commonly seen in myelofibrotic disorders, including agnogenic myeloid metaplasia, polycythemia vera, and essential thrombocythemia. It occurs most commonly in the liver and spleen but may occur on rare occasions in lymph nodes, on serosal surfaces, in the urogenital system, in paraspinal or epidural spaces, or in the lung. Whether EMH in the lung represents in situ embryonic cell differentiation or a compensatory delivery of hematopoietic cells from the marrow is unclear. Lung involvement can present with a variety of nonspecific symptoms, including cough, slowly progressive dyspnea, and pulmonary hypertension (PH) with signs of right-sided heart failure, and can progress to acute respiratory failure and death. PH can result from a number of mechanisms, including pulmonary capillary obstruction, thrombotic events, interstitial pneumonitis and fibrosis, and alveolar airspace involvement, or from hematopoietic progenitor cell invasion of the PA intima. Radiographically, findings can range from isolated lung or paravertebral masses to diffuse increased interstitial markings with septal thickening, alveolar airspace filling with ground-glass opacities as in our case, or pleural effusions with or without hemothorax. The osseous structures (in particular, the ribs) typically show expansion of the medullary cavity. In some instances, EMH of the lung may show no evidence of radiographic abnormality. This underscores the need for a heightened awareness of these multiple radiographic presentations in patients with chronic myeloid disorders to make this rare diagnosis. Technectium-99 (99mTc) sulfur colloid scintigraphy can be strongly suggestive of the diagnosis, although false-negatives have been reported. A total of seven cases diagnosed by 99mTc sulfur colloid scintigraphy exist in the literature. As such, little can be said about the sensitivity or specificity of this test in the diagnosis of this entity.