Figures
Figure 1. Physical examination revealed a soft, mobile, subcutaneous mass (about 3 cm) in the left buccal region (arrows).
Figure 2. Contrast-enhanced computed tomography revealed an infiltrative soft-tissue mass measuring 3.1 × 1.5 × 3.5 cm, centered in the masticator space with effacement of fat planes between the masseter, pterygoid, and temporalis muscles.
Figure 3. An intraoral incisional biopsy under general anesthesia with obtained specimen (arrows). The intraoral approach allowed direct access to the bucco-masseteric space while avoiding external scarring.
Figure 4. H&E stain (× 40) demonstrating a diffuse, vaguely nodular infiltrate, expanding the soft tissue and disrupting normal architectural boundaries. Note the presence of mild plasmacytic differentiation (arrows). H&E: hematoxylin and eosin.
Figure 5. (a) Representative immunohistochemistry demonstrating diffuse CD20 positivity in the neoplastic B cells within the masticator-space lesion (× 200). (b) Bcl-2 staining highlights strong cytoplasmic expression in the small B cells, supporting a diagnosis of EMZL rather than reactive hyperplasia (× 200). EMZL: extranodal marginal zone B-cell lymphoma.
Figure 6. (a) CD3 negativity in the tumor cell population confirms that the predominant infiltrate is of B-cell rather than T-cell lineage (× 200). (b) Lack of CD5 expression helps to exclude mantle cell lymphoma and most chronic lymphocytic leukemia/small lymphocytic lymphoma (× 200). (c) The neoplastic lymphoid infiltrate is negative for CD10, supporting a marginal zone origin and helping exclude follicular lymphoma (× 200). (d) The neoplastic lymphoid population is negative for CD23 expression, helping distinguish this case from small lymphocytic lymphoma (× 200). (e) CD43 negativity in the neoplastic B cells is consistent with an EMZL phenotype and argues against other small B-cell lymphomas (× 200). (f) Bcl-6 negativity in the neoplastic lymphoid cells (× 200). This lack of Bcl-6 expression supports a post-germinal center origin and helps exclude follicular lymphoma. EMZL: extranodal marginal zone B-cell lymphoma.
Figure 7. CD21 outlining disrupted follicular dendritic cell meshworks consistent with follicular colonization (arrows).