Unexpected Discrepancies in the Histopathological and Microbiological Diagnoses of Suspected Mucormycosis Cases at a South Indian Tertiary Care Center During the COVID-19 Pandemic.

Introduction Mucormycosis is an uncommon fungal infection caused by filamentous fungi of the Mucorales order, namely Rhizopus, Lichthemia, andMucor species. The incidence and prevalence of mucormycosis reached an all-time high during the COVID-19 pandemic due to excessive steroid use and other factors, leading to the coining of the term CAM (COVID Associated Mucormycosis). The diagnosis of mucormycosis is by a combination of histopathology and microbiological techniques, such as KOH mount and culture. Although microbiological and histopathological findings usually correlate, certain discrepancies are known to occur and are discussed in our study. The aim of our research is to study the correlation between histopathology and microbiology findings, as well as their respective merits and limitations, in suspected mucormycosis cases in COVID-19 patients at a tertiary healthcare center in South India. Methods It is a retrospective study, where data from 74 COVID-19 patients admitted in the ENT ward between June 2021 and August 2021 with a suspicion of mucormycosis was collected. Samples from these patients were sent to the pathology and microbiology departments of Rangaraya Medical College. KOH mount, culture on Saboraud's Dextrose Agar (SDA), and histopathology findings were analyzed. Results Histopathology and culture findings of Mucormycosis were correlated in 64 isolates (86.5%), including five cases (6.7%) of mixed infections, where the culture was positive for only a single type of fungus. In the remaining 10 isolates, discrepancies were observed, accounting for 13.5% of the total sample size. Pearson's correlation coefficient test did not reveal any statistically significant correlation in the case of histopathology and microbiology culture or KOH mount, further highlighting the presence of discrepancies. The high correlation between KOH mount and culture isolates (100%) in our study is attributable to the processing of the same sample by the microbiology department. On the other hand, the correlation between histopathology and culture in our study is 86.5%, and the expected correlation as suggested by previous studies is only 50%. These discrepancies between culture and histopathology could be due to different samples being sent to the two departments. Conclusion  Although fungal cultures are considered the gold standard, they have drawbacks such as slow growth, and the potential for both false positives and false negatives. KOH mount is a rapid and cost-effective method, but it lacks specificity and sensitivity. Histopathology offers the advantage of specific species identification and assessment of tissue inflammation; however, it is an invasive procedure and poses challenges in accurately identifying the fungus. A multidisciplinary approach, with coordination between physicians, surgeons, pathologists, clinical microbiologists, and radiologists, is essential for timely diagnosis and management. For accurate identification of the causative organism, it is recommended to send the same sample for histopathological examination, KOH mount, and culture.