Riedel’s thyroiditis in a 78 year old male: a rare experience.

We present a rare case of Riedel ’s thyroiditis in a 78-year-old male, native of hilly region of Nepal who presented with chief complaint of long standing swelling of the thyroid with discharging sinus. Right hemithyroidectomy with excision of sinus was done. Gross examination showed asymmetrically enlarged right lobe of thyroid with adherent fibroadipose and muscular tissue. Microscopy revealed diffuse hyalinised fibrosis of the thyroid parenchyma with presence of variable number of atrophic to few normal thyroid follicles in between. The stroma showed dense lymphoplasmacytic infiltration with foci of calcifications and hemorrhage. There was extension of fibrosis beyond the thyroid capsule, encasing the skeletal muscle bundles at many places. Diagnosis of Riedel’s thyroiditis was made.Riedel’s thyroiditis is a rare entity but can occasionally be encountered. Various imaging modalities may not be helpful for the definite diagnosis. Diagnostic thyroidectomy should be performed for the accurate diagnosis and further management. DOI: 10.21276/APALM.1392