{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,10,29]],"date-time":"2025-10-29T12:24:52Z","timestamp":1761740692052,"version":"build-2065373602"},"reference-count":19,"publisher":"MDPI AG","issue":"2","license":[{"start":{"date-parts":[[2025,1,7]],"date-time":"2025-01-07T00:00:00Z","timestamp":1736208000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["JCM"],"abstract":"<jats:p>Background: Medullary carcinoma of the small intestine is an exceptionally rare subtype of gastrointestinal cancer, characterized by its solid growth pattern and lack of glandular structures, which complicate timely diagnosis. During the COVID-19 pandemic, diagnostic delays for rare cancers became increasingly common due to the prioritization of COVID-related cases and patient reluctance to seek medical attention. Methods and Result: We present the case of a 70-year-old male initially misdiagnosed with COVID-19, whose persistent symptoms led to the eventual discovery of medullary carcinoma. Imaging studies revealed focal lesions in the liver, spleen, and thickened small intestinal walls, prompting surgical resection of a 16 cm intestinal segment. Histopathological examination confirmed medullary carcinoma with lymph node and liver metastases, supported by immunohistochemistry, which showed positive markers (calretinin, pancytokeratin, cytokeratin 7) and excluded other malignancies. Conclusions: The diagnostic delay, exacerbated by the pandemic, highlights the challenges of distinguishing rare cancers from more common conditions during global health crises. This case underscores the importance of advanced diagnostic techniques, such as immunohistochemistry, for accurate identification. Maintaining robust cancer diagnostic pathways during emergencies is crucial to avoid delays in treatment. Future research should focus on improving screening methods for rare cancers and developing resilient healthcare systems to mitigate similar challenges in future crises.<\/jats:p>","DOI":"10.3390\/jcm14020298","type":"journal-article","created":{"date-parts":[[2025,1,7]],"date-time":"2025-01-07T03:38:41Z","timestamp":1736221121000},"page":"298","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":2,"title":["Diagnostic Challenges of Medullary Carcinoma of the Small Intestine During the COVID-19 Pandemic"],"prefix":"10.3390","volume":"14","author":[{"given":"Danuta","family":"Szkudlarek","sequence":"first","affiliation":[{"name":"Pathology Department, Provincial Hospital Center of the Jelenia G\u00f3ra Valley, 58-506 Jelenia G\u00f3ra, Poland"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Katarzyna","family":"Sk\u00f3rkowska-Telichowska","sequence":"additional","affiliation":[{"name":"Department of Non-Surgical Clinical Sciences, Faculty of Medicine, Wroc\u0142aw University of Science and Technology, Wybrze\u017ce Wyspia\u0144skiego 27, 50-370 Wroc\u0142aw, Poland"},{"name":"Department of Endocrinology, Jerzy Gromkowski Regional Specialist Hospital, Koszarowa 5 Str., 51-149 Wroc\u0142aw, Poland"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-1404-2274","authenticated-orcid":false,"given":"Benita","family":"Wiatrak","sequence":"additional","affiliation":[{"name":"Department of Pharmacology, Faculty of Medicine, Wroc\u0142aw Medical University, 50-345 Wroc\u0142aw, Poland"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2025,1,7]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","unstructured":"Barsouk, A., Rawla, P., Barsouk, A., and Thandra, K.C. 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