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NBME 23 Answers

nbme23/Block 2/Question#20

A 47-year-old woman has had a goiter for 10 months. ...

Replacement of thyroid parenchyma by lymphoid cells

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Remember on histology Hashimoto's thyroiditis has two distinct features Hürthle cells(which are eosinophilic metaplastic cells that line follicles) and lymphoid aggregates with germinal centers.(pg. 338, FA 2019) The correct answer describes the latter feature of Hashimoto's.

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submitted by chris07(15),

I'm guessing that since this is hashimoto's that a biopsy of the thyroid would show the thyroid gland completely engulfed by attacking lymphocytes. Over time though, wouldn't the thyroid be completely destroyed and fibrotic?

dr.xx  Progressive thyroid cell damage can change the apparent clinical picture from goitrous hypothyroidism to that of primary hypothyroidism, or "atrophic" thyroiditis. https://www.ncbi.nlm.nih.gov/books/NBK285557/ The pathological features are atrophic thyroid gland with lymphocytic infiltration and fibrous tissue replacing normal thyroid parenchyma. https://www.researchgate.net/publication/302196286_Atrophic_Thyroiditis +  
paulkarr  I was thinking that "Diffuse fibrosis" was trying to point to IgG4 Riedel Thyroiditis rather than Hashimoto's. +1