Solitary Extramedullary Plasmacytoma of the Head and Neck: A Report of Three Cases Treated With Curative Radiotherapy and a Review of the Dose-Control Relationship

Abstract

Solitary plasmacytoma is an uncommon hematologic malignancy characterized by the monoclonal proliferation of abnormal plasma cells in the bone or extramedullary tissues and the absence of other multiple myeloma-defining clinical characteristics. Mostly, solitary extramedullary plasmacytoma (SEP) occurs in the head and neck region, also called solitary extramedullary plasmacytoma of the head and neck (SEPHN). Although the standard of care for SEPHN is not well established, either a surgical approach or localized external beam radiotherapy (EBRT) can be used as a definitive treatment. Due to the high radiosensitivity of SEPHN, EBRT has been associated with adequate therapeutic effects in the management of SEP, with the advantage of being a noninvasive modality that yields high rates of local control with a reasonable toxicity profile. We present a case series of three patients with SEPHN treated with EBRT at our institution with clinical outcomes.

Keywords: 3-d radiotherapy; head and neck neoplasms; laryngeal neoplasms; larynx preservation; multiple myeloma treatment; nasopharyngeal neoplasm; oropharyngeal neoplasms; plasma cell tumor; radical radiotherapy; solitary extramedullary plasmacytoma (sep).

Figure 1. Radiation treatment plan illustrating 3DCRT beam arrangement for laryngeal plasmacytoma; red, PTV; green, mandible; white, spinal cord; pink, esophagus.

3DCRT, three-dimensional conformal radiation therapy; PTV, planning target volume

Figure 2. Computed tomography showing the base of the tongue nodular lesion (arrow).

Figure 3. Isodose distribution of the prescribed dose throughout the irradiated treatment volume at the base of the tongue and normal tissue: yellow, 100%; green, 95%; and blue, 80%.

Figure 4. Computed tomography showing no enhancing lesions consistent with complete response.

Figure 5. Computed tomography showing a contrast-enhancing mass in the left nasopharynx (arrow).

Figure 6. High-power view (40×) revealing the proliferation of atypical plasmacytoid cells with focal pleomorphism.

The cells demonstrate medium to large size with a round nucleus, centrally and eccentrically located, with dense cytoplasm and a clear perinuclear zone in the region of the Golgi apparatus (arrows).

Figure 7. Isodose distributions in color wash representing the dose distribution throughout the treatment volume in the nasopharynx and normal tissue: yellow, 100%; green, 95%; and blue, 80%.

Figure 8. Computed tomography showing no abnormal enhancing lesions in the nasopharynx.