A 45-year-old woman presents to the clinician for evaluation of her progressively increasing weakness and dyspnea for the past 3 months. In addition, she has had dysphagia for 2 months, initially for solid foods, which gradually progressed to liquid foods. On examination, her temperature is 37.2 C, pulse rate is 90/min, respirations 18/min and blood pressure 115/80 mmHg. Lung auscultation reveals bilateral basilar crackles. Contrast-enhanced computed tomography reveals a mediastinal mass originating from the thymus with a size of 10 × 8 cm. Laboratory tests show-

Hemoglobin- 8.1 g/dL with a normocytic anemia

Erythrocyte count- 2.1 million/uL

Reticulocyte count- Normal range

WBC count- Normal range

Platelet count- Normal range

Iron and B12 levels- Normal range

Which of the following findings will be present on the microscopic examina­tion of her bone marrow biopsy?