What is the difference between undifferentiated and poorly differentiated nasopharyngeal carcinoma

WHO divides nasopharyngeal carcinoma into 3 types: keratinizing squamous cell carcinoma; non-keratinizing squamous cell carcinoma; undifferentiated carcinoma. The WHO revised in 1991 divides nasopharyngeal carcinoma into 2 types: keratinizing squamous cell carcinoma; non-keratinizing carcinoma (differentiated type; undifferentiated type). The most important difference between them is whether there is obvious evidence of keratinization. The former has obvious keratinization, which is more common in the elderly and is not closely related to Epstein-Barr virus infection. The latter accounts for the majority of nasopharyngeal carcinomas and has no obvious keratinization. They (especially the undifferentiated type) are closely related to Epstein-Barr virus infection. In non-keratinizing carcinomas, the differentiated cancer cells have clear boundaries and are arranged in multiple layers or paving shapes, while the undifferentiated cancer cells have unclear boundaries and are fused, and some are spindle-shaped. Non-keratinizing carcinomas (especially the undifferentiated type) often have abundant lymphocyte infiltration.

Domestic classification The more authoritative classification in China divides NPC into two categories: carcinoma in situ and invasive carcinoma. Invasive carcinoma includes five subtypes: microinvasive carcinoma, squamous cell carcinoma (high, medium and low differentiation), adenocarcinoma (high, medium and low differentiation), vesicular cell carcinoma and undifferentiated carcinoma. This classification is often used in domestic pathological diagnosis.

Histological features of common nasopharyngeal carcinoma types

Most carcinomas in situ occur in the surface epithelium, and a few occur in the crypt epithelium. Most carcinomas in situ are found between columnar epithelium (columnar carcinoma in situ); a few are located in squamous epithelium (squamous carcinoma in situ). Carcinoma in situ can involve the entire epithelium or only part of the epithelium. The diagnosis of nasopharyngeal carcinoma in situ is mainly based on cytological criteria, followed by histological characteristics. Carcinoma in situ cancer cells are negative or very weakly positive in CK immunohistochemical staining and AB mucus staining, which can distinguish carcinoma in situ from normal, atypical hyperplasia and metaplastic cells, the latter of which are positive for CK and AB staining.