Immune System

Thymus - Mineralization

Narrative
Comment:
Mineralization does not typically occur as a primary lesion in the thymus. However, it can occur secondary to renal and/or parathyroid disease (metastatic mineralization) or with thymic necrosis (dystrophic mineralization). This lesion is characterized by variable amounts of densely basophilic, amorphous, and/or granular material (Figure 1 and Figure 2, arrows). Mineral may occur as multifocal lesions within the thymus with renal or parathyroid disease or may occur within necrotic foci.
Recommendations:
Thymic mineralization should be diagnosed and graded if associated with renal and/or parathyroid disease. Mineralization associated with thymic necrosis should not be diagnosed separately unless warranted by severity, but should be described in the pathology narrative.
References:

National Toxicology Program. 1999. NTP TR-469. Toxicology and Carcinogenesis Studies of AZT (CAS No. 30516-87-1) and AZT/α-Interferon A/D in B6C3F1 Mice (Gavage Studies). NTP, Research Triangle Park, NC.

Abstract: https://ntp.niehs.nih.gov/go/6082

Pearse G. 2006. Histopathology of the thymus. Toxicol Pathol 34:515-547.

Full Text: http://tpx.sagepub.com/content/34/5/515.long

Stefanski SA, Elwell MR, Stromberg PC. 1990. Spleen, lymph nodes, and thymus. In: Pathology of the Fischer Rat: Reference and Atlas (Boorman GA, Eustis SL, Elwell MR, Montgomery CA, MacKenzie WF, eds). Academic Press, San Diego, 369-394.

Ward JM, Mann PC, Morishima H, Frith CH. 1999. Thymus, spleen, and lymph nodes. In: Pathology of the Mouse (Maronpot RR, ed). Cache River Press, Vienna, IL, 333-360.

  • Image of mineralization in the thymus from a male B6C3F1/N mouse in a chronic study

    Thymus - Mineralization in a male B6C3F1/N mouse from a chronic study (higher magnification of Figure 1). Mineralized foci are characterized by variably sized, densely basophilic, amorphous material (arrows).

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Thymus - Mineralization in a male B6C3F1/N mouse from a chronic study. Multiple mineralized foci (arrows) are present within the thymic medulla.
Thymus - Mineralization in a male B6C3F1/N mouse from a chronic study. Multiple mineralized foci (arrows) are present within the thymic medulla.
Thymus - Mineralization in a male B6C3F1/N mouse from a chronic study (higher magnification of Figure 1). Mineralized foci are characterized by variably sized, densely basophilic, amorphous material (arrows).
Thymus - Mineralization in a male B6C3F1/N mouse from a chronic study (higher magnification of Figure 1). Mineralized foci are characterized by variably sized, densely basophilic, amorphous material (arrows).

Authors

Kristen Hobbie, DVM, PhD
Principal Pathologist
Huntingdon Life Sciences
Peterborough, UK

Susan A. Elmore, MS, DVM, DACVP, DABT, FIATP
Staff Scientist, NTP Pathologist
NTP Pathology Group
National Toxicology Program
National Institute of Environmental Health Sciences
Research Triangle Park, NC

Holly M. Kolenda-Roberts, DVM, PhD, DACVP
Veterinary Pathologist
SNBL USA
Everett, WA

Reviewers

Jerrold M. Ward, DVM, PhD, DACVP, FIATP
Veterinary Pathologist
Global VetPathology
Montgomery Village, MD

Robert R. Maronpot, DVM, MS, MPH, DACVP, DABT, FIATP
Senior Pathologist
Experimental Pathology Laboratories, Inc.
Research Triangle Park, NC