DIAGNOSTIC CHALLENGE  Intraoral mass in the posterior maxillary vestibule Francisco Samuel Rodrigues Carvalho, DDS; Fábio Wildson Gurgel Costa, DDS, PhD; Filipe Nobre Chaves, DDS; Ana Paula Negreiros Nunes Alves, DDS, PhD; Fabrício Bitu Sousa, DDS, PhD; Régia Maria do Socorro Vidal do Patrocínio, MD, MSc; Karuza Maria Alves Pereira, DDS, PhD THE CHALLENGE A 42-year-old woman came to our clinic for consultation regarding a painful swelling inside her mouth that had developed over approximately 1 month. During this time, the patient had no recurrent fever, generalized malaise, or weight loss. The patient reported that her most recent dental visit had been 15 days ago, and since that time, her oral discomfort had worsened. The patient’s primary care profes- sional previously had prescribed amoxicillin (500 milligrams); however, after completing the 7-day drug regimen, the patient continued to have symptoms. An oral health care professional at our clinic observed a smooth, painful, soft, sessile nodular mass with well-defined margins in the posterior maxillary vestibule sulcus (Figure 1). The clinician also observed heavily decayed teeth and clinical signs of periodontal disease. The patient had a history of un- treated myelodysplastic syndrome (MDS) and nonspecific heart murmur, and she was taking folic acid to treat severe anemia. In addition, the patient had no history of cancer, alcohol consumption, smoking, or hospitalizations. An overview of the patient’s panoramic radiograph revealed multiple lost teeth, root residues, heavily decayed teeth with periapical radiolucent lesions, horizontal bone resorption in the jaws, and bone sclerosis in the periapical area of tooth no. 34 (Figure 2). The clinician did not observe any radiographic changes in the area corresponding to the nodular lesion. The patient’s preoperative blood screening showed the following results (Table): low values for red blood cell count, hemoglobin, and hematocrit; increased mean corpuscular volume; low values for white blood cell and platelet counts; and increased clotting time. The clinician performed an oral incisional biopsy and submitted the specimen for histopathologic evaluation. The histopathologic analysis revealed diffuse sheets of large cells with ovoid and sometimes hyperchromatic nuclei, scarce cytoplasm, mild mitotic activity, and necrotic foci, resulting in a preliminary diagnosis of lympho- proliferative disorder (Figure 3). The clinician performed an immunohisto- chemical analysis using the antibodies PAX-5, terminal deoxynucleotidyl transferase (TdT), CD3, CD79a, CD34, CD117, and myeloperoxidase (MPO). The results were positive in 90% of cells for MPO (Figure 4), diffuse positive for CD117, focal positive in rare cells for CD3 and TdT, positive in plasmo- cytes for CD79a and in vessels for CD34, and negative for PAX-5. The results of a cytogenetic study showed deletion in the long arm of chromosome 11 in 4 metaphases (that is, del[11][q32]). ORIGINAL CONTRIBUTIONS 544 JADA 146(7) http://jada.ada.org July 2015