The head and neck encompass a wide array of pathologic lesions, including nonneoplastic lesions, as well as benign and malignant neoplasms. Among the many neoplastic proliferations occurring in the head and neck, epithelial neoplasms of the upper aerodigestive tract are the most common and represent the lesion type that the surgical pathologist is most often confronted with on a day-to-day basis. This issue of Pathology Case Reviews focuses on selective squamous epithelial lesions of the upper aerodigestive tract with the intent of discussing key diagnostic features and differential diagnoses.
Arguably, premalignant epithelial lesions of the upper aerodigestive tract (UADT) represent the most challenging diagnostic problem in head and neck pathology. Premalignant epithelial lesions include nonkeratinizing dysplasias and keratinizing dysplasias. Both “types” of dysplastic alterations of the UADT mucosa are graded in a similar manner as uterine cervical dysplasias including mild, moderate, and severe dysplasia with dysplastic changes involving one-third, two-thirds, and the entire epithelial surface (ie, carcinoma in situ), respectively. This paradigm of grading epithelial dysplasia is applicable to the nonkeratinizing dysplasias of the UADT where invasive carcinoma develops as a continuum from severe dysplasia. In this context, the use of the term carcinoma in situ as classically defined (ie, full thickness epithelial dysplasia) is appropriate and applicable. Unfortunately, relative to the mucosa of the UADT, the nonkeratinizing dysplasias are less common than the keratinizing dysplasias. Potential problems in grading the keratinizing dysplasias relate to the fact that invasive carcinoma may develop (and often does) from dysplastic changes limited to the lower (basal) zone in the absence of full thickness dysplasia (ie, classically defined carcinoma in situ). As such, the grading of epithelial dysplasia can be subjective and determining which dysplastic lesions have the potential to invade the submucosa problematic. In one article, I attempt to address these issues, including comparing and contrasting the nonkeratinizing and keratinizing dysplasias, discussing the alterations relative to keratinizing dysplasias that can be classified as severe dysplasia, addressing the use of the designation carcinoma in situ in relation to keratinizing dysplasia, and discussing the clinical import of the diagnosis of epithelial dysplasia. In this article, I offer the proposal to grade UADT epithelial dysplasia in a two-tiered manner similar to uterine cervical dysplasia, including low-grade squamous epithelial lesion for mild dysplasia and high-grade squamous epithelial dysplasia to include both moderate and severe dysplasia.
Aside from intraepithelial dysplasias, another potential diagnostic problem in mucosal lesions of the UADT is the identification and diagnosis of microinvasive carcinoma. At present, there is no single definition for microinvasive carcinoma, but irrespective of its defining characteristics (ie, depth of invasion), a diagnosis of microinvasive carcinoma is predicated on the presence of neoplastic epithelium, in nests and/or individual cells, within the superficial aspect of the submucosa. As a continuum of the article on keratinizing dysplasia, (microinvasive) carcinoma develops from dysplasia that may be limited to the lower (basal) epithelial zone only. In this article, I present a case of microinvasive carcinoma discussing its diagnostic parameters, differential diagnosis, and therapeutic and prognostic significance.
Fine needle aspiration biopsy (FNAB) is the initial diagnostic modality of choice when confronted with a superficial lesion of the head and neck, including a lateral cervical neck mass, a salivary gland mass, and a thyroid-related mass lesion. The diagnostic issues related to cystic squamous cell lesions of the lateral cervical neck are potentially problematic and controversial. These problems not only revolve around the FNAB diagnosis but may also occur after surgical resection of the neck lesion. Drs. Cohen and Wenig address the cytologic and histologic diagnostic issues in their case report of a metastatic cystic squamous cell carcinoma. Further, a frequent dilemma in the diagnosis of metastatic cystic squamous cell carcinoma to the lateral cervical neck is the apparent absence of a primary source for the metastasis (ie, occult primary neoplasm). This manuscript also addresses the clinical and pathologic issues relative to the occult primary neoplasms of the head and neck, as well as discussing the existence of a primary branchiogenic carcinoma. In addition, the authors discuss the utility of p16 immunostaining (in cytologic and histologic material) in the identification of the primary carcinoma in the setting of the occult primary and metastatic carcinomas of the head and neck.
Nasopharyngeal carcinomas (NPC) represent subtypes of “conventional” squamous cell carcinoma with rather unique clinical features, etiologic factors, histomorphologic findings, and therapeutic and prognostic import. Dr. John Chan, in an excellent comprehensive overview, discusses numerous issues relative to NPC, including histologic subtyping emphasizing the usual as well as unusual morphologic findings that can be found in association with NPC. Among the less common features that can be seen in NPC that may engender diagnostic difficulties are crush artifact, presence of tumor-associated amyloid globules, papillary architecture, mucin-positive cells, prominent inflammatory cell infiltrate and/or granulomatous inflammation, and benign cellular components mimicking NPC. Given the fact that the primary therapeutic modality in the treatment of the majority of NPC is by radiation treatment, the pathologist is often confronted with posttreatment changes that may create diagnostic challenges. Dr. Chan discusses the diagnostic parameters of evaluating posttreatment tissue sampling of NPC that may assist the pathologist in recognizing neoplastic cells or in recognizing benign cellular components that may simulate the presence of carcinoma and potentially result in misdiagnoses.
In addition to the “conventional” type of squamous cell carcinoma and NPC, there are a variety of morphologic subtypes of squamous cell carcinoma with specific clinical and pathologic features. In an excellent comprehensive overview, Dr. Mary Richardson presents the array of variants of UADT squamous cell carcinoma, including verrucous carcinoma, papillary squamous cell carcinoma, spindle cell squamous carcinoma, basaloid squamous cell carcinoma, adenosquamous carcinoma, adenoid squamous cell carcinoma, undifferentiated carcinoma, and giant cell carcinoma.
I would like to extend my gratitude to all the contributors to this monograph. It is my hope that the readership of Pathology Case Reviews find the topics presented in this monograph informative and useful in their daily practice.