Patient's Query
Hello doctor,
I am a 36-year-old male that was being treated for intestinal or peritoneal TB. My understanding is that the diagnostic criteria for malignancy of epithelial is stromal invasion. Immunohistochemistry is used to identify the type of cancer once it is shown there is a malignancy. If you have not proven the histologic criteria for malignancy in mesothelial tissue but you do have an expression of immunohistochemistry markers that identify colon cancer (specifically MDX2 and CK20) does this prove malignancy? If it is diagnostic for malignancy, what is the potential rationale for not listing these markers (MDX2 and CK20) or other type-specific markers? Kindly help.
Hello doctor,
Welcome to icliniq.com.
Your understanding of the criteria for malignancy is precise, that there has to be a stromal invasion in case of epithelial cancer. But sometimes it is difficult to identify stromal invasion because the epithelial cells are not apparent on light microscopy in the stroma. During such circumstances, the IHC can help mark the epithelial cells in the stroma. Also, the IHC profile of various types of cells shows overlap with other cells such that it cannot be interpreted as merely positive and negative, it has to be correlated with light microscopy. I hope this has helped you. Thank you.
Patient's Query
Hello doctor,
From my understanding, the report concludes the tissue is malignant but does not state how the pathologist concluded the tissue is malignant vs benign (e.g. evidence of invasion). It also concludes that the malignancy is likely of colorectal origin based on the IHC of (+)CK20, (-)CDX-2, and (-)CK7. What light microscopy features would they have had to see in order to conclude this is malignant tissue vs benign? Would they need to see stromal invasion to conclude this definitively? I am a 36-year-old male that was being treated for intestinal or peritoneal TB. Clinical symptoms were consistent with intestinal TB: stenotic ileocecal valve, CT scans strongly suggest TB vs Crohn's (short segment involvement, no comb-sign, no-fibro fatty proliferation, etc.). Biopsies of the IC valve lesion (from 2 colonoscopies) showed inflammation with no dysplasia/carcinoma (no granulomas). Quantiferon-gold test for TB was negative but had spent the last 3 years in a TB endemic area. CT scans also showed plaque-like thickening of the omentum and peritoneum. After 4 months of anti-TB treatment CT scans showed increasing omental thickening and limited improvement of the ileocecal lesion (improvement in cecum only, no change and mild worsening in ileum). US core needle biopsy was performed on the omentum, biopsy concluded adenocarcinoma of colorectal origin. Exploratory laparoscopy was performed to assess the extent of the disease showing many white tumors covering the peritoneum/omentum. Mild short segment dilation of the ileum was noted, but the exterior surface of the ileum/cecum is otherwise normal. Laparoscopy and CT scans do not show metastases other than in the omentum. Surgical pathology again concluded adenocarcinoma of colorectal origin (attached). In summary, a profile is mostly consistent with TB but would suggest an atypical location of primary colon cancer and metastatic spread. Based on the pathology reports provided, is it at all possible that pathologists could have confused a benign process for a malignancy? Or is the differentiation between adenocarcinoma and a benign process stark to make confusion very difficult? Also, could the histologic presentation of TB peritonitis in omental tissue mimic that of an adenocarcinoma? Kindly help.
Hello,
Welcome back to icliniq.com.
Based on the reports you have attached (attachment removed to protect the patient's identity), there is no doubt that the lesion is malignant. The benign process can be easily differentiated from the malignant process by light microscopy only. The doubt here on light microscopy was whether this is a primary tumor of the mesothelial origin or colorectal origin, for which IHC (markers) were done. The profile of CK20+, MDX2+, and CK7- is definitive of colorectal origin. In no circumstances can this be TB? Besides this is a primary colorectal tumor that has spread to the omentum. So this is distant metastasis of a primary tumor. In such cases, there is no need to stress stromal invasion. Stromal invasion is used when the tumor is limited to the primary site.
Patient's Query
Hello doctor,
Based on your answer that benign processes are easy to differentiate from malignant processes, I assume that I am somehow interpreting the referenced article incorrectly. Can you help me understand why the article's statement? It is well known that reactive mesothelial proliferations may mimic mesothelioma (or metastatic carcinoma) is this not applicable to this situation?
Hello,
Welcome back to icliniq.com.
Reactive mesothelial proliferations (benign) can confuse with mesotheliomas (malignant). But TB of omentum (benign) cannot be confused with mesotheliomas or colorectal carcinomas. That has typical histology. I hope this has helped you. Thank you.
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Answered byDr. Ashish Vilas Jawarkar
Medically reviewed byDr. K. Shobana
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