About Us
The TPS lab provides the following services:
  • Specialized necropsy support, providing services that include intravascular perfusion, study design, fixative choice, and harvest of difficult to identify/obtain tissues
  • Specialized trimming of nervous system components including the brain, spinal cord, spinal nerve roots and associated ganglia, peripheral nerves and components of the autonomic nervous system.
Phone: 301-378-0505

Email: mbutt@toxpath.net

Tox Path Specialists, LLC (TPS) was founded in July 2007 to provide preclinical neuropathology and neurohistology support to companies and other institutions developing neuroactive pharmaceuticals, devices, and other therapies with emphasis on therapies being delivered directly to the central and peripheral nervous systems. Although primarily involved with studies involving the nervous system, Tox Path Specialists, LLC also provides general morphologic pathology support.

The president and chief scientific officer of TPS is Mark T. Butt, DVM, Diplomate, American College of Veterinary Pathologists. Dr. Butt has more than 20 years experience evaluating the nervous system in a wide variety of laboratory species. Prior to founding Tox Path Specialists, Dr. Butt was a neuropathologist for Pathology Associates (PAI) for 13 years and for the last six of those years, was the General Manager of PAI with full financial and professional oversight of an organization with over 200 employees and 35 veterinary pathologists.
          - H&E for basic morphology
          - Luxol Fast Blue for myelin
          - Bielschowsky's silver for axons/neurofilamentous structures
          - other stains as needed​
          - GFAP staining for astrocytes
          - IBA-1 staining for microglial cells
          - neurofilament structures (various stains as required)
          - staining for neuronal subsets (CGRP, Tyrosine Hydroxylase, etc.)
          - full coronal sections of brains/spinal cords/other tissues
          - skin biopsy specimens for the determination of intraepidermal nerve fiber 
Other professional services include stereologic investigations on nervous system (and occasionally other) tissues for the purpose of quantifying neuronal number and density in the brain and various ganglia, determining nerve fiber size and myelin ratios (in peripheral nerves), area fraction calculations for structures including amyloid plaques and myelin, neuronal/glial cell size determinations, intraepidermal nerve fiber density and other quantitative parameters that require measurement in the brain, spinal cord, ganglia or nerves.

TPS is fully GLP compliant and maintains an in-house Quality Assurance Unit directed by Laura Caccese.
Dr. Butt is a national/international speaker and consultant on the morphologic assessment of neuroactive drugs, therapies and devices; a neuropathology consultant for many of the largest pharmaceutical and contract research organizations in the world; the author of numerous scientific articles on the nervous system; and the co-editor and co-author of the reference book Fundamental Neuropathology for Pathologists and Toxicologists: Principles and Techniques (J. Wiley and Sons, publisher). He has evaluated over 400 studies with specific neuropathology endpoints, most studies supporting regulatory submissions for new and/or altered therapies for nervous system disorders. In addition to neuropathologic assessments, Dr. Butt provides support for protocol development/study design. 

​Click here to download Dr. Mark Butt's resume.

Dr. Butt is supported by a laboratory with full general histology and specific neurohistology capabilities. The laboratory is headed by Dave Hodge, HT(ASCP) with over 25 years experience in histology and laboratory management. Mr. Hodge was the former laboratory director at Pathology Associates.