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Specimen Submission Guidelines for Pathologic Evaluation of Rash- and Eschar-Associated Illness

Download: CDC—10369 Specimen Submission Guidelines for Pathologic Evaluation of Rash- and Eschar- Associated Illness [PDF – 324 KB]

Pathogens that cause rashes or eschars may be distributed focally and sparsely in the skin, despite extensive inflammatory infiltrates in the involved tissues. Because cutaneous lesions often occur in the context of systemic diseases (e.g. Rocky Mountain spotted fever or meningococcemia), collecting an adequate biopsy or autopsy specimen of the involved skin, and in the case of fatal illnesses, tissue samples from any other organ system with significant inflammatory findings, ensures the best chance of detecting the causative agent. Performance of specific immunohistochemical, molecular, or other assays will be determined using clinical and epidemiologic information provided by the submitter and the histopathologic features of the submitted tissue specimens. Digital images can be particularly useful in guiding subsequent laboratory evaluations of rash- or eschar-associated diseases.

Collection of Tissue Specimens

The preferred specimens include a minimum of one (1) paraffin block of the cutaneous lesion, or an appropriate biopsy specimen in formalin (i.e., wet tissue). Fresh-frozen tissue may also be submitted for culture and molecular-based assays; it is generally recommended that these represent separately biopsied tissues rather than a single bisected biopsy. Specific guidelines for these samples include:

  1. Minimally, a 3 mm punch, deep shave, or excisional biopsy specimen from the eschar or a representative rash lesion. If multiple stages or forms of cutaneous lesions are identified, multiple biopsies should be submitted.
  2. If a rash is identified in the context of a systemic fatal illness, representative tissues should be included from any other organ showing significant gross or microscopic pathology.

Submission of Specimens

Paraffin-embedded tissue blocks

In general, this is the preferred specimen and is especially important to submit in cases where tissues have been in formalin for a significant time. Prolonged fixation (>2 weeks) may interfere with some immunohistochemical and molecular diagnostic assays.

Wet tissue

If available, we highly recommend that unprocessed tissues in 10% neutral buffered formalin be submitted in addition to paraffin blocks.

Unstained slides

Although not optimal, if paraffin blocks are unavailable it may be possible to utilize unstained sections cut at 3–5 microns (10 slides per block) for immunohistochemistry and special stains but not molecular diagnostic assays (e.g. PCR).

Fresh-frozen tissue

Send separately on dry ice.

Electron Microscopy (EM) specimens

Samples fixed in glutaraldehyde and held in phosphate buffer. Sample containers are filled to the top with phosphate buffer and sent on wet ice. Do not freeze. Epoxy-embedded tissues are also accepted.

Please refer to our General Guidelines for shipping pathology specimens.

Photomicrograph of an immunohistochemical stain of tissue infected with Rickettsia rickettsii

This is a photomicrograph of an immunohistochemical stain of tissue from a patient infected with Rickettsia rickettsii, the causative agent of Rocky Mountain Spotted Fever (RMSF). The red staining represents the bacteria.