Multi‐UniFocality (MUF), in contrast to multifocality, in thyroid lesions: Relation to lymphocytic thyroiditis

Pathology International, vol. 74, pp. 274–284

Abstract

Whereas multifocality typically concerns papillary thyroid carcinoma (PTC) without specification of intrathyroidal metastatic or independent nature of tumor foci, the designation of the latter as Multi-UniFocal (MUF) may be relevant for select cases. A case series involving multifocal thyroid lesions with divergent histopathological morphology and/or molecular profile, with molecular evaluation of multiple individual tumor foci per patient based on a next-generation sequencing approach, was retrospectively reviewed. Twenty-five patient cases with multifocal thyroid lesions suggestive of MUF, with 2-6 (median 3) tumor foci per patient, were described. Tumor lesions comprised diverse histopathology, including PTC, (E)FVPTC, NIFTP, FA, FTC, and oncocytic. Morphologically similar and/or diverse tumor foci harbored different molecular alterations (suggestive of non-shared clonality); with(out) coexistent similar foci harboring identical molecular alterations; or (partly) shared molecular alterations. MUF was associated with chronic lymphocytic thyroiditis in almost half of the cases. The recognition of MUF may justify the independent clinical consideration per individual tumor focus; as separate lesions albeit within a multifocal context. The potential clinical relevance and prognostic value of MUF remain to be further established.

Authors 2

1. Mehtap Derya Aydemirli Aachen Department of Pathology Leiden University Medical Center Leiden The Netherlands Department of Pathology, Leiden University Medical Center

   Leiden University Medical Center

   Affiliation as printed

   Department of Pathology Leiden University Medical Center Leiden the Netherlands

   Department of Pathology, Leiden University Medical Center, Leiden, the Netherlands

2. Hans M. Morreau corresponding Aachen Department of Pathology Leiden University Medical Center Leiden The Netherlands Department of Pathology, Leiden University Medical Center

   Leiden University Medical Center

   Affiliation as printed

   Department of Pathology Leiden University Medical Center Leiden the Netherlands

   Department of Pathology, Leiden University Medical Center, Leiden, the Netherlands