Application of the Milan System for Reporting Pediatric Salivary Gland Cytopathology: Analysis of histologic follow-up, risk of malignancy, and diagnostic accuracy

Abstract

Background: The diagnosis and management of salivary gland tumors in pediatric patients can be challenging. The utility of fine-needle aspiration (FNA) cytopathology and the performance of the Milan System for Reporting Salivary Gland Cytopathology (MSRSGC) in this age group have not been systematically assessed. The paucity of data has contributed to the controversial role of FNA cytopathology in the presurgical management of these patients.

Methods: The authors retrospectively analyzed 104 pediatric salivary gland FNAs (2000-2020). A correlation with the available histopathologic follow-up (n = 54) was performed. The distribution percentages, the risk of neoplasm (RON), and the risk of malignancy (ROM) were assessed for each category of the MSRSGC.

Results: The overall sensitivity, specificity, negative predictive value, and positive predictive value of pediatric salivary gland FNAs were 80%, 97%, and 92%, respectively. The RON values for the nondiagnostic, nonneoplastic, atypia of undetermined significance, benign neoplasm, salivary gland neoplasm of uncertain malignant potential, suspicious for malignancy, and malignant categories were 60%, 11%, 100%, 100%, 100%, 100%, and 100%, respectively, whereas the ROM values were 0%, 11%, 100%, 6%, 67%, 100%, and 100%, respectively. The percentage of nonneoplastic FNAs was greater in comparison with the adult population (52% vs 8%). All neoplasms in patients aged 0 to 10 years were malignant, whereas benign neoplasms occurred only in patients aged ≥11 years; this supported an inverse correlation between age and malignancy rate in salivary gland neoplasms.

Conclusions: FNA cytopathology demonstrates excellent diagnostic performance in differentiating malignant and benign pediatric salivary gland lesions. The MSRSGC is a valuable tool for standardization of the reporting and preoperative risk stratification of these lesions.

Keywords: Milan System for Reporting Salivary Gland Cytopathology (MSRSGC); fine-needle aspiration (FNA); pediatric; risk of malignancy (ROM); risk of neoplasm (RON); salivary gland.

Figure 1.

Cytopathologic-histologic correlation of a case of metastatic melanoma with unknown primary site involving an intraparotid lymph node from an 18-year-old male. (A) Fine-needle aspiration (FNA) of an enlarged intraparotid lymph node demonstrated a population of large, pleomorphic cells with granular, hyperchromatic nuclei and conspicuous nucleoli (H&E, original magnification X600). (B) Immunohistochemistry performed on the cell block preparation demonstrated positivity for HMB45 in a small subset of tumor cells (immunohistochemistry, original magnification X400). (C) Surgical resection of the parotid gland showed an intraparotic lymph node with effaced architecture and extensive necrosis (H&E, original magnification X20). (D) Clusters of pleomorphic neoplastic cells with cytologic features similar to those on FNA smear were best seen in the subcapsular region (H&E, original magnification X600).

Figure 2.

Cytopathologic-histologic correlation of a case of pediatric follicular lymphoma arising in an intraparotid lymph node from a 14-year-old male. Fine-needle aspiration (FNA) demonstrated a mixed population of mature lymphocytes intermixed with numerous tangible body macrophages and scattered eosinophils on both (A) Diff-Quik (original magnification X200) and (B) H&E preparations (original magnification X600), cytologic features that overlap with those seen in reactive lymph nodes. However, flow cytometry detected a population of CD10-positive monotypic B cells, prompting a diagnosis of “atypical lymphoid infiltrate”. (C) Surgical resection showed partial effacement of nodal architecture with expansile follicles (lower left) and a rim of residual normal lymph node architecture at the periphery (upper right) (H&E, original magnification X40). (D) A monotonous population of small to intermediate sized lymphocytes with intermixed tangible macrophages were best seen within expansile follicles (H&E, original magnification X600).

Figure 3.

Cytopathologic-histologic correlation of a case of secretory carcinoma arising in the parotid gland from a 11-year-old female. (A) Fine-needle aspiration (FNA) demonstrated frequent clusters of polygonal epithelial cells forming acinar-like structures. Tumor cells exhibited ovoid-to-round nuclei, finely granular cytoplasm with abundant small vacuoles, and occasional intracytoplasmic mucin (Diff-Quik, original magnification X600). (B) Clusters of tumor cells forming papillary structures with clear to eosinophilic cytoplasm and more frequent intracytoplasmic mucin were present in the cell block preparation (H&E, original magnification X400). (C) Surgical resection showed proliferation of bland tumor cells with papillary and acinar architectures. Intracytoplasmic eosinophilic colloid-like material was evident (H&E, original magnification X400). (D) By immunohistochemistry, the tumor cells were positive for S-100 (immunohistochemistry, original magnification X100).

Figure 4.

Incidence of MSRSGC diagnoses by age. (A) Accumulative curves of different MSRSGC categories by age from 0 to 21 years. (B) Distribution of MSRSGC categories in two age groups (age 0–10 versus age 11–21 years).