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Paget΄s disease and squamous cell neoplasms are the most common anal disorders to be evaluated by frozen section analysis. Pathologists may be asked to evaluate margin status since their microscopic extent is often greater than is grossly appreciated. Paget΄s disease may be mimicked by other entities, including reactive squamous cells, koilocytes, and melanocytic proliferations. In situ squamous neoplasms also display features that simulate invasion in frozen sections. [ABSTRACT FROM AUTHOR]

Appendiceal tumors are rarely diagnosed preoperatively, and their classification is both challenging and controversial owing to their tendency to disseminate in the peritoneal cavity despite their frequent low-grade appearance. Frozen section analysis may be requested to assess the status of the appendiceal margin, determine whether extra-appendiceal epithelium is present, and to classify extra-appendiceal disease as low- or high-grade. Other types of appendiceal epithelial tumors, such as serrated neoplasms, should be distinguished from mucinous tumors, since they tend to precede overtly malignant peritoneal disease (peritoneal carcinomatosis). Goblet cell carcinoid tumors often spread to non-contiguous structures and, thus, may prompt intraoperative consultation. [ABSTRACT FROM AUTHOR]

Intraoperative assessment of colon cancer resection specimens may influence immediate surgical management. Indications for evaluation include determining the depth of invasion, presence of serosal penetration, status of margins, and intactness of the mesorectum, when present. Pathologists may also be asked to identify residual carcinoma in neoadjuvantly treated patients, or document the presence of other lesions, such as adenomas, polypectomy sites, or underlying colitis. Estimating the depth of invasion into the colonic wall is best achieved by macroscopic examination in combination with frozen section analysis, whereas detecting serosal involvement may require touch or scrape preparations of the serosal surface. Assessment of margins is most challenging in rectal specimens, particularly when patients have received neoadjuvant therapy. [ABSTRACT FROM AUTHOR]

Several types of mesenchymal and hematopoetic neoplasm may involve the colorectum. Although a definitive diagnosis is rarely made at the time of frozen section analysis, it is important for the pathologist to be familiar with common mesenchymal and hematopoetic tumors so that they may facilitate surgical management and appropriately triage tissue for ancillary studies. The most common mesenchymal tumors of the colon are gastrointestinal stromal tumors, but neoplasms that recapitulate the phenotypes of smooth muscle cells, Schwann cells, and fibroblasts also develop in this location. Most hematopoetic neoplasms that involve the colon are B-cell lymphomas, and they may affect either immunocompetent or immunocompromised individuals. [ABSTRACT FROM AUTHOR]

Secondary involvement of the colon by other malignant neoplasms may mimic primary colorectal carcinoma and results from direct extension, peritoneal seeding, or hematogenous spread. Careful gross examination and key histologic features may suggest the presence of a metastasis. Most primary tumors are solitary mucosa-based lesions, whereas secondary neoplasms may be multiple and often substantially affect the outer colonic wall. Primary colorectal cancers are comprised of malignant cribriform glands with necrosis and show dysplasia in the overlying mucosa, whereas secondary tumors show variable growth patterns and readily detectable lymphovascular invasion. Several benign processes, namely diverticulitis and intestinal endometriosis, may also mimic colon cancers and their nature may not be apparent prior to surgical intervention. [ABSTRACT FROM AUTHOR]

The most common indication for intraoperative consultation among pediatric patients with gastrointestinal symptoms is evaluation for the possibility of Hirschsprung΄s disease. Intraoperative documentation of ganglion cells, or their absence, is crucial to the immediate management of the patient. Unfortunately, detecting ganglion cells in colonic samples obtained from neonatal patients may be challenging for a number of reasons, not the least of which is their immature appearance in frozen section samples. [ABSTRACT FROM AUTHOR]

Although radiographic studies usually provide accurate preoperative staging information in colorectal cancer patients, intraoperative frozen section evaluation of extracolonic tissues may be requested in order to confirm the diagnosis of a metastasis or ensure its complete resection. The liver represents the most common site of distant organ metastases from colorectal cancer. Several benign lesions may simulate liver metastases, most notably von Meyenberg complexes and bile duct hamartomas. Peritoneal carcinomatosis is also an important intraoperative finding that may alter the surgical management of colon cancer patients. A number of mimics of peritoneal carcinomatosis are encountered in the frozen section laboratory. [ABSTRACT FROM AUTHOR]