Fine Needle Aspirate Flow Cytometry's Ancillary Utility in Diagnosing Non-Hodgkin Lymphoma in the Head and Neck.

Background: While ultrasound-guided fine-needle aspiration cell block (FNACB) is a cost-effective, expeditious, and reliable procedure used routinely in the initial evaluation of head and neck masses, it has limited efficacy in diagnosing lymphoproliferative disorders such as non-Hodgkin lymphoma (NHL). Flow cytometry performed on an fine-needle aspiration (FNA) sample [ultrasound-guided fine-needle aspirate flow cytometry or flow cytometry performed on an FNA sample (FNAFC)], has been shown to be a valuable adjunct to FNACB in the diagnosis of lymphoproliferative disorders of the spleen, kidney, and thyroid. The objective of this study was to appraise FNAFC's utility as an ancillary tool to detect NHL arising in the head and neck region in adult patients.

Methods: This is a retrospective study involving 52 adult patients with head and neck lymphadenopathies and masses suspicious for lymphoproliferative disorders, who underwent ultrasound-guided FNACB and ultrasound-guided FNAFC between January 2017 and November 2022. Patient demographics, FNACB histopathological and immunophenotypic results, postoperative histopathology results (when available), and follow-up information until May 2023 were reviewed.

Results: Of the 52 FNACB samples, 23 samples (44.2%) yielded a diagnosis negative for carcinoma, 20 samples (38.5%) were nondiagnostic on account of scant cellularity, 8 samples (15.4%) were suspicious for malignancy, and a single sample (1.9%) was compatible with malignancy. Regarding FNAFC samples, 37 samples (71.2%) were diagnosed as showing no evidence for a lymphoproliferative disorder, 4 samples (7.7%) as nondiagnostic because of insufficient cell count, 4 samples (7.7%) as suspicious for a lymphoproliferative neoplasm, and 7 samples (13.5%) as compatible with a lymphoproliferative neoplasm, most frequently a B-cell lymphoma. 7 of the 11 patients (63.6%) with a suspicious/positive FNAFC result underwent excisional biopsy for additional work up. Postoperative histopathology reports corroborated FNAFC's findings in 6 patients (85.7%), while the remaining patient's (14.3%) suspicious FNAFC result was discordant with postoperative histopathology results. The other 4 patients (36.4%) did not require excisional biopsy as the hemato-oncologist deemed the information provided by the FNAFC as sufficient for the diagnosis and treatment of an NHL in the specific clinical contexts of those patients. All patients with nondiagnostic (due to insufficient cell count), inconclusive, or negative FNAFC (ie, nondiagnostic of a lymphoproliferative disorder) were followed up for a mean follow-up period of 11.9 months (range: 61.2 months; SD: 10.2 months), during which no new lymphadenopathies/masses nor progression was observed.

Conclusions: FNAFC is a useful and practical supplementary tool in the diagnosis of lymphoproliferative disorders in the head and neck region, principally B-cell lymphoma. While conventional FNACB offers a valuable insight into the initial work up of head and neck masses, FNAFC can routinely detect small abnormal cell populations. Furthermore, in specific clinical contexts, it can reliably diagnose NHL, thereby averting the need for an excisional biopsy in a subset of patients.