Case #387 – January 2015

Case Description

A 71-year-old female presented to her health care provider with a nodule on her back. The nodule was removed and sent to Pathology for histological work-up. Tissue was sectioned, stained with hematoxylin-and-eosin (H & E) and examined by the attending pathologist and in turn forwarded to the CDC-DPDx for diagnostic assistance. A brief pathology report indicated a possible helminth infection. Figure A was taken at 100x, Figures B and C at 200x, and Figure D at 400x magnification. What is your diagnosis? Based on what criteria?

Figure A

Figure B

Figure C

Figure D

This was a case of sparganosis caused by the third stage plerocercoid larva (sparganum) of a cestode in the genus Spirometra. Diagnostic features include:

a thick tegument.
the presence of calcareous corpuscles (best seen at 200x and 400x magnification).
an absence of hooklets or defined protoscoleces helps to rule out echinococcosis, cysticercosis, and coenurosis.

Dogs, cats and other predatory mammals normally serve as the definitive host. Humans become accidental paratenic hosts by ingestion of water contaminated with infected copepods or consumption of raw or undercooked infected amphibians, reptiles, or fish.