A 12-year-old boy is brought to a clinic in equatorial Africa with a rapidly enlarging, painless mass involving his right mandible. He has also experienced recent weight loss and low-grade fevers. Past medical history is negative. Physical examination reveals a firm, fixed 6-cm mass of the jaw and several enlarged cervical lymph nodes. An incisional biopsy of the jaw mass is performed.
Which of the following is the most likely microscopic finding?
The correct answer is:
C) Monomorphic intermediate-sized lymphocytes with "starry sky" appearance
This patient is presenting with the endemic (African) form of Burkitt Lymphoma, which characteristically involves the jaw or facial bones in children. The sporadic form, more common in the United States, typically presents as an abdominal mass (e.g., ileocecal region). Both forms are highly aggressive B-cell lymphomas with a very high proliferation rate (Ki-67 index often >99%). The classic microscopic appearance is described as a "starry sky." The "sky" consists of a dense, monomorphic sheet of intermediate-sized malignant B-cells. The "stars" are tingible body macrophages which are large, pale phagocytic cells that have ingested apoptotic debris from the rapidly dividing (and dying) tumor cells.
Answer choice A: Diffuse sheets of large lymphocytes, is incorrect. This describes diffuse large B-cell lymphoma (DLBCL). While also aggressive, the cells in DLBCL are significantly larger and lack the characteristic starry sky architecture of Burkitt lymphoma.
Answer choice B: Large multinucleated cells, is incorrect. This describes Reed-Sternberg cells seen in Hodgkin lymphoma. Hodgkin lymphoma typically presents with contiguous lymphadenopathy and B-symptoms but does not usually involve the jaw.
Answer choice D: Nodular aggregates with Bcl-2, is incorrect. This is the hallmark of follicular lymphoma. In contrast to Burkitt lymphoma, follicular lymphoma is an indolent cancer where cells fail to die due to the t(14;18) translocation involving the anti-apoptotic BCL2 gene.
Answer choice E: Smudge cells, is incorrect. This is the classic finding for chronic lymphocytic leukemia (CLL), a mature B-cell neoplasm that primarily affects older adults and presents with an absolute lymphocytosis.
Key Learning Point
Burkitt lymphoma is a high-grade B-cell neoplasm (CD19+, CD20+) associated with the t(8;14) translocation, which moves the c-myc proto-oncogene to the immunoglobulin heavy chain (IgH) locus. This leads to the constitutive expression of c-myc, a transcription factor that promotes rapid cell growth. The endemic form is nearly 100% associated with Epstein-Barr virus (EBV).
