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Intestinal inflammatory pseudotumour with regional lymph node involvement: identification of a new bacterium as the
1Department of Pathology, Queen Elizabeth Hospital, Hong Kong. cheuk_wah@hotmail.com
Abstract:
Inflammatory pseudotumours are the morphological expression of diverse processes such as reactive/reparative, infective, and neoplastic. This paper reports an example of intestinal inflammatory pseudotumour, with identification of a newly characterized bacterium in the lesion. The patient presented with intestinal obstruction. Laparotomy revealed a tumour in the terminal ileum causing stricture, and multiple enlarged regional lymph nodes. Histologically, the tumour and lymph nodes were composed of plump spindle cells disposed in a vague storiform pattern, and associated with lymphocytes and plasma cells. Immunohistochemical studies showed that most of the spindle cells were histiocytes (CD68 positive), prompting a search for a bacterial aetiology, akin to mycobacterial spindle cell pseudotumour. All histochemical stains for micro-organisms were unrewarding. Ultrastructural studies, however, revealed abundant bacteria within the spindle histiocytes. Polymerase chain reaction, using conserved oligonucleotide primers complementary to the 16S rRNA genes of eubacteria, was employed to amplify 16S rRNA gene fragments directly from the involved lymph node tissue. Phylogenetic analysis of the amplified DNA sequences revealed an organism with 99% sequence conformity to Pseudomonas veronii, a bacterium which has hitherto not been implicated in human infection. The importance of searching for an infective agent in inflammatory pseudotumour in the appropriate setting is re-emphasized.
Insights
This study identifies a novel bacterium, Pseudomonas veronii, within an intestinal inflammatory pseudotumor. This finding highlights the importance of investigating infectious agents in diagnosing inflammatory pseudotumors.
Area of Science:
- Gastroenterology
- Pathology
- Microbiology
Background:
- Inflammatory pseudotumors (IPTs) represent a diverse group of conditions including reactive, infectious, and neoplastic processes.
- Intestinal IPTs can cause significant complications such as obstruction.
Observation:
- A case of intestinal obstruction due to an ileal IPT is presented.
- Histological examination revealed spindle cells, identified as histiocytes (CD68 positive), with associated inflammatory cells.
- Standard stains for microorganisms were negative, but ultrastructural analysis showed bacteria within histiocytes.
Findings:
- Polymerase chain reaction and phylogenetic analysis identified a novel bacterium, Pseudomonas veronii, in the lymph node tissue.
- This bacterium had 99% sequence conformity to Pseudomonas veronii, previously not implicated in human infections.
Implications:
- This case underscores the significance of considering and actively searching for infectious etiologies in IPTs.
- The identification of Pseudomonas veronii expands the spectrum of bacteria associated with human disease.