“PEEPING BUGS” in a Pathologist’s Microscope: A Case Series

Salony Mittal¹, Kiranjot Kaur², Anshu Gupta Devra³, Devyani Pendharkar⁴, Neema Tiwari⁵, Saumya Harsh Mittal⁶

^1–4Department of Pathology, School of Medical Sciences and Research, Sharda University, Greater Noida, Uttar Pradesh, India

⁵Department of Pathology, Post Graduate Institute of Child Health, Noida, Uttar Pradesh, India

⁶Department of Medicine, School of Medical Sciences and Research, Sharda University, Greater Noida, Uttar Pradesh, India

Corresponding Author: Saumya Harsh Mittal, Department of Medicine, School of Medical Sciences and Research, Sharda University, Greater Noida, Uttar Pradesh, India, Phone: +91 9663414840, e-mail: saumya.mittal@sharda.ac.in

Received: 15 August 2024; Accepted: 28 October 2024; Published on: 31 December 2024

ABSTRACT

The nonneoplastic infective lesions are infrequently studied and under-documented in histopathology literature despite their common occurrence in developing countries like India. So, we enlisted and analyzed the cases from the last 6 months at our tertiary care hospital to emphasize the clinical and histomorphological clues to infective etiologies. The spectrum of the lesions encountered ranged from bacterial to fungal to viral to even parasitic infestations.

Keywords: Case report, Fungal infections, Infections, Mycoses, Parasites, Worms

How to cite this article: Mittal S, Kaur K, Devra AG, et al. “PEEPING BUGS” in a Pathologist’s Microscope: A Case Series. J Med Acad 2024;7(2):77–79.

Source of support: Nil

Conflict of interest: None

Patient consent statement: The author(s) have obtained written informed consent from the patient for publication of the case report details and related images.

INTRODUCTION

Histopathology plays a crucial role in the diagnosis of infectious organisms. Often, detection of the exact etiological agent causing an infective lesion is difficult or missed by direct microscopy, especially by amateur pathologists. Infective etiological agents have specific features that can act as pointers in leading to a definitive diagnosis of the pathogen. Hence, this case series highlights the morphological clues that can raise a suspicion of infection and recalls the specific telltale signs of pathogens.

CASE DESCRIPTION

The histopathological evaluation of a case begins with the clinical presentation, age of the patient, site of biopsy, and history of immunocompromised states like diabetes, corticosteroid intake, human immunodeficiency virus (HIV), or cancer chemotherapy, as well as microscopic clues. The type of inflammatory reaction (acute or chronic), presence or absence of eosinophils, presence of granulomas (tubercular or foreign body type), and presence of suspicious structures with chitinous walls, eggs, or cysts with lamellated walls hint at the presence of infection, which could be bacterial, viral, or fungal.

We compiled a list of infective cases reported at our center in the last 6 months, from July to December 2023, and reviewed the slides and requisition forms. The summary of the cases is given in Table 1, and microscopic images of a few cases are shown in Figures 1 to 3.

**Table 1:** Summary of cases with age, sex, site of biopsy, clinical presentation, and histopathological diagnosis
Case number	Age/sex	Site	Clinical presentation	Histopathological diagnosis
1	48 y/F	Rectal tissue	Large rectal ulcers	Amebic proctitis
2	32 y/M	Nasal polyp	Nasal obstruction and epistaxis	Rhinosporidiosis
3	22 y/M	Amputated left hand little finger	Gangrene, H/O diabetes	Mucormycosis
4	27 y/M	Anal ulcer	Discharging ulcer at anal verge, HIV positive	HSV infection in anal ulcer
5	50 y/M	Right maxillary sinus	Sinusitis, H/O diabetes	Mucormycosis
6	55 y/M	Excised liver left lobe	Hepatic abscess	Amebic liver abscess
7	12 y/F	Middle ear cavity	Chronic suppurative otitis media	Actinomycosis
8	46 y/F	Maxillary sinus	Sinusitis, H/O diabetes	Mucormycosis
9	34 y/F	Hepatic cysts	Hydatid cyst	Hydatid cyst
10	36 y/F	Gastric biopsy	Pangastritis	H. pylori gastritis
11	38 y/F	Nasal mass	Nasal obstruction	Aspergillosis
12	72 y/F	Hepatic cysts	Hydatid cyst	Hydatid cyst
13	20 y/F	Vocal cord polyp	Hoarseness of voice	Aspergillosis
14	50 y/M	Hard mass over plantar aspect of right foot	Soft tissue sarcoma	Fungal mycetoma
15	20 y/F	Ceacal ulcer edge	Abdominal TB	Amebic colitis

Figs 1A to C: (A) Amebic colitis—hematoxylin and eosin (400×) microscopic picture of trophozoites of Entamoeba histolytica in colon showing hemophagocytosis; (B) Aspergillosis—hematoxylin and eosin (400×) microscopic picture showing presence of septate branching hyphae (at acute angle) of Aspergillus; (C) Mucormycosis—hematoxylin and eosin (400×) microscopic picture showing presence of broad hyphae of mucor, branching at obtuse angle

Fig. 2: H. pylori MGG—(oil immersion) microscopic picture showing spiral-shaped organism in the gastric mucosa

Fig. 3 Hydatid cyst. Hematoxylin and eosin (100×) microscopic picture showing presence of cyst wall composed of three layers: outermost pericyst, laminated membrane, and innermost germinal layer

DISCUSSION

The clinical presentation, age, and immunocompromised status of the case, combined with the histopathological examination of the tissue specimen from the site involved, definitely help in reaching an effective diagnosis in infections. The precise location and distribution of different organ-specific pathogens hint at the etiological agent.

The infections can be bacterial, viral, fungal, or parasitic. Depending on the type of inflammatory reaction, whether acute or chronic, and the presence of granulomas (caseating or foreign body type), one can suspect the infective agent.

The presence of eosinophils can be indirect evidence of an underlying fungal infection. Certain morphological cues that help in the differentiation of types of fungi are the size, presence of a capsule (Histoplasma) or not, presence of septation, and the angle of branching, for example, broad obtuse angle branching (Mucor species) or thin septa with acute angle branching (Aspergillus), and budding forms (Candida) or spores.¹

Certain bacterial infections, like actinomycosis, nocardiosis, and botryomycosis, can be easily mistaken for mycosis due to the presence of filamentous forms. Actinomycosis, caused by Actinomyces israelii, can lead to abscess formation in multiple sites. It can be confused with mycosis due to the presence of filamentous forms showing the Splendore–Hoeppli phenomenon. However, the key differentiating feature is positivity on Gram’s stain but negativity on Ziehl–Neelsen stain.² Similarly, Nocardia is also positive with Gram stain and weakly positive with acid-fast stain.³ The differentiation of bacterial infections from true mycoses is essential for appropriate treatment, as bacterial infections can be treated with antibiotics and surgical debridement.⁴

Infections of the gastrointestinal tract may vary from viral infections, like Herpes simplex virus (HSV) and cytomegalovirus in the esophagus, to Helicobacter pylori in the stomach, to amebic colitis in the intestine.⁵ Presence of Cowdry bodies, multinucleated cells with margination of chromatin, and nuclear molding are telltale signs of herpetic infection. The presence of amebic trophozoites should be especially noted in exudates of the intestinal ulcer. The trophozoites revealing erythrophagocytosis are a diagnostic hallmark of amebic infection.⁶

H. pylori infection presents with features of gastritis and ulcer formation and appears as spiral bacilli evident in Warthin–Starry staining. Hydatid cysts can be easily identified on gross examination as pearly white membranous structures. Hence, the world of bugs and parasites is enticing and alluring to a pathologist’s eye and can be camouflaged by various pointers known to an experienced eye.⁶

CONCLUSION

The histopathologist needs thorough knowledge of the morphology of microorganisms, their telltale signs, and also the utility of histochemical stains to rule out their close mimics. The surrounding tissue response, the accompanying inflammatory cells, and correlation with relevant clinical details are the keys to reaching the actual etiological agent.

REFERENCES

1. Chandler FW, Watts JC. Fungal diseases. In: Damjanov I, Linder J, editors. Anderson’s Pathology. 10th ed. St. Louis: Mosby; 1996. pp. 951–962.

2. Sullivan DC, Chapman SW. Bacteria that masquerade as fungi: actinomycosis/nocardia. Proc Am Thorac Soc 2010;7:216–221. DOI: 10.1513/pats.200907-077AL

3. Guarner J, Brandt ME. Histopathologic diagnosis of fungal infections in the 21st century. Clin Microbiol Rev 2011;24:247–280. DOI: 10.1128/CMR.00053-10

4. Gupta E, Bhalla P, Khurana N, et al. Histopathology for the diagnosis of infectious diseases. Indian J Med Microbiol 2009;27(2):100–106. DOI: 10.4103/0255-0857.49423

5. Bai S, Maykel JA, Yang MX. Inflammatory pseudotumor associated with HSV infection of rectal vascular endothelium in a patient with HIV: a case report and literature review. BMC Infect Dis 2020;20:234. DOI: 10.1186/s12879-020-04960-5

6. Yue B, Meng Y, Zhou Y, et al. Characteristics of endoscopic and pathological findings of amebic colitis. BMC Gastroenterol 2021;21:367. DOI: 10.1186/s12876-021-01941-z

________________________
© The Author(s). 2024 Open Access. This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (https://creativecommons.org/licenses/by-nc/4.0/), which permits unrestricted use, distribution, and non-commercial reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.