Update on Neuroendocrine Carcinomas of the Larynx

Carolina Strosberg, MD; Alfio Ferlito, MD, DLO, DPath, FRCSEd ad hominem, FRCS (Eng, Glasg, Ir) ad eundem, FDSRCS ad eundem, FACS, FHKCORL, FRCPath, FASCP, IFCAP; Asterios Triantafyllou, PhD (Lond), FRCPath; Douglas R. Gnepp, MD; Justin A. Bishop, MD; Henrik Hellquist, MD, PhD, SAPath (Stockh), FRCPath; Primoz Strojan, MD, PhD; Stefan M. Willems, MD, PhD; Göran Stenman, DMD, PhD, FRCPath; Alessandra Rinaldo, MD, FRCSEd ad hominem, FRCS (Eng, Ir) ad eundem, FRCSGlasg, FACS; Juan C. Hernandez-Prera, MD

Disclosures

Am J Clin Pathol. 2019;152(6):686-700. 

In This Article

Poorly Differentiated Neuroendocrine Carcinoma of the Larynx

Poorly differentiated neuroendocrine carcinomas are the second most common type of laryngeal neuroendocrine carcinoma. These tumors tend to occur in middle-aged male patients with history of heavy tobacco smoking.[30] Paraneoplastic syndromes, including carcinoid, Eaton-Lambert, ACTH, or Schwartz-Bartter syndromes, may occur.[22] Similar to other laryngeal neuroendocrine carcinomas, the supraglottic area is most commonly affected and hoarseness and dysphagia are usual symptoms.[30] This group is further subdivided into small cell neuroendocrine carcinoma and large cell neuroendocrine carcinoma.[9]

Histologically, small cell neuroendocrine carcinoma is a submucosal cellular proliferation usually associated with surface ulceration and arranged in solid nests, sheets, or ribbons with absence of a prominent fibrovascular stromal component Image 3A. The neoplastic cells are small to medium sized and have scant cytoplasm with oval to spindled hyperchromatic nuclei lacking nucleoli and showing nuclear molding Image 3B. Confluent areas of tumor necrosis and individual cell necrosis are common, as well as numerous mitoses, well in excess of 10 mitoses per 2 mm2 or 10 hpfs.[9] The Azzopardi phenomenon or effect (a basophilic granular nuclear DNA coating in or on blood vessel walls) is also considered a classic feature of these tumors.[31] Lymphovascular and perineural invasion are common. In rare cases, an admixture of small cell neuroendocrine carcinoma and either squamous cell carcinoma or adenocarcinoma can occur; these cases are designated as combined or composite tumors.[6] Notably, although previously reported in the literature and accepted by the 2005 WHO classification, the terms "combined" and "composite tumors" were not specifically mentioned as a separate category in the updated 2017 WHO Classification of Head and Neck Tumors when referring to poorly differentiated neuroendocrine carcinomas of the larynx.[9]

Image 3.

Poorly differentiated neuroendocrine carcinoma, small cell type. A, Low magnification shows a submucosal hypercellular tumor with nested, solid, and trabecular growth with necrosis associated with mucosal ulceration (x20). B, Tumor cells with scant cytoplasm and indistinct cellular borders, and oval to spindled nuclei with densely hyperchromatic chromatin. Nuclear molding, mitotic activity, and apoptotic bodies are readily observed (x400). C, Tumor invades adjacent thyroid cartilage (x20). D, Insulinoma-associated protein 1 nuclear immunoreactivity confirms neuroendocrine differentiation (x200).

As in small cell neuroendocrine carcinomas of other organ systems, tumors arising in the larynx are immunoreactive for AE1/AE3 and CAM5.2 and often show a perinuclear (punctate, dot-like) staining pattern. High-molecular-weight cytokeratins (CK5/6 and CK903) and p63 are typically negative but may be focally positive.[32,33] Neuroendocrine markers, including synaptophysin, CD56, and neuron specific enolase, are positive, whereas chromogranin may be only focally positive or negative and more recently INSM1 has been reported as a reliable marker of neuroendocrine differentiation in these tumors Image 3D.[14,34] TTF-1 may show nuclear staining in some cases.[35]

Small cell neuroendocrine carcinoma must be distinguished from other basaloid tumors, including oropharyngeal human papillomavirus (HPV)-related nonkeratinizing squamous cell carcinoma and adenoid cystic carcinoma, particularly the solid type. HPV-related nonkeratinizing squamous cell carcinoma characteristically arises in the oropharynx and not in the larynx.[36] However, in some cases an oropharyngeal primary can extend into the supraglottis and clinically mimic an endolaryngeal tumor. HPV-related nonkeratinizing squamous cell carcinoma exhibits a submucosal lobulated growth pattern lacking marked stromal desmoplasia Image 4A. The tumor cells also have scant cytoplasm and oval to spindled hyperchromatic nuclei, but show a more syncytial architecture due to the absence of distinct cell borders Image 4B. Brisk mitotic activity and abundant apoptotic bodies are easily identified. As its name implies, overt keratinization is not a common feature.[37–39] Virtually all HPV-related nonkeratinizing squamous cell carcinomas are diffusely positive for p16 and harbor actively transcribed high-risk HPV, in particularly HPV-16 or HPV-18 Image 4D.[37,38] HPV-related nonkeratinizing squamous cell carcinoma lacks evidence of neuroendocrine differentiation and is consistently positive for p63/p40 and CK5/6 Image 4C.[24] Although, a small subset of oropharyngeal HPV-related carcinomas can exhibit neuroendocrine differentiation (discussed below). Adenoid cystic carcinoma and small cell carcinoma share some cellular features, that is, scant, cytoplasm, hyperchromatic nuclei, and absence of nucleoli Image 5A and Image 5B. In addition, in solid adenoid cystic carcinoma, increased mitotic activity and necrosis are typically present. Immunohistochemistry also assists in separating these tumors, because solid adenoid cystic carcinoma is consistently negative for synaptophysin, chromogranin, and TTF-1, and shows variable p63 and smooth muscle actin (myoepithelial cells) and CD117 (luminal cells) positivity Image 5C and Image 5D.[33,40–42] Furthermore, adenoid cystic carcinoma is characterized by specific gene rearrangements, involving MYB or MYBL1, which is diagnostic.[43]

Image 4.

Human papillomavirus-related nonkeratinizing squamous cell carcinoma. A, Tumor involving laryngeal surface epiglottis growing in solid sheets with some trabeculae and cords formation (x10). B, Tumor cells with scant cytoplasm and oval to spindled hyperchromatic nuclei arranged in a syncytial growth pattern showing increased mitotic activity (x200). C, p63 highlights the uninvolved mucosal surface and the carcinoma underneath (x40). D, Strong and diffuse cytoplasmic and nuclear reactivity for p16 (x200).

Image 5.

Adenoid cystic carcinoma of the larynx. A, Submucosal tumor with predominant cribriform growth pattern (x20). B, Tumor cells with scant cytoplasm with fairly uniform angulated hyperchromatic nuclei (x400). Occasional true lumens are identified. Dual luminal-abluminal cell differentiation highlighted by (C) p63 immunoreactivity in myoepithelial/abluminal cells (x400) and (D) CD117 reactivity in ductal/luminal cells (x400).

The implications of a diagnosis of small cell carcinoma are critical, as these are highly lethal tumors with a dismal 5-year survival of 5%.[30] Patients usually present with advanced disease (66.7% with stage IV) due to early distant metastases.[15] Metastases to regional lymph nodes are also common, and up to 90% of patients develop distant metastases to liver, lung, bone, and brain. Due to the extent of the disease, surgical resection plays a minor role in management of these tumors and most patients undergo chemoradiation therapy, which has been shown to give the highest 5-year DSS in comparison with other treatment modalities.[15,30]

Large cell neuroendocrine carcinoma is the second subtype of poorly differentiated neuroendocrine carcinomas whose diagnostic criteria and existence have been controversial. The 2005 WHO classification of head and neck tumors did not recognize large cell neuroendocrine carcinoma as a distinctive category and classified it within the spectrum of "atypical carcinoid."[18] To date, fewer than 50 cases of large cell neuroendocrine carcinomas of the larynx have been reported in the literature. They tend to occur in men with an average age of 59 years. The majority of tumors arise in the supraglottic region and presenting symptoms may include hoarseness, dysphagia, odynophagia, otalgia, weight loss, heartburn, and cervical adenopathy. Most patients have history of heavy tobacco smoking.[8,26,40]

The diagnosis of large cell neuroendocrine carcinoma follows strict criteria. First, the tumors should show typical neuroendocrine architecture including organoid nesting, trabecular growth, rosettes, and peripheral palisading Image 6A. Secondly, the tumor cells should be medium to large size with moderate to abundant cytoplasm. Marked cellular pleomorphism, vesicular chromatin, and small to prominent nucleoli are characteristic features Image 6B. Numerous mitosis and comedo necrosis are easily identified (>10 mitosis per 2 mm2 or 10 hpfs).[9] Like small cell neuroendocrine carcinoma, large cell neuroendocrine carcinoma is positive for cytokeratins (especially low molecular weight) and at least one neuroendocrine marker (synaptophysin, chromogranin, or INSM1) according to the 2017 WHO classification; however, some experts advocate for two positive neuroendocrine markers Image 6C.[9,14,34,40]

Image 6.

Poorly differentiated neuroendocrine carcinoma, large cell type. A, Submucosal cellular tumor with nested and solid growth (x40). B, Tumor cells with moderate eosinophilic cytoplasm and round to oval nuclei, with vesicular chromatin and prominent nuclei (x400). Numerous mitosis, apoptotic bodies, and comedo-type necrosis are identified. Strong staining for (C) synaptophysin and (D) p16 (x40).

Tumors whose histologic features overlap with those of large cell neuroendocrine carcinoma include moderately differentiated neuroendocrine carcinomas and basaloid squamous cell carcinoma. Moderately differentiated neuroendocrine carcinoma can have a growth pattern similar to large cell neuroendocrine carcinoma displaying rosettes and nesting; mitotic count is the main criteria separating these two entities (2–10 vs >10 mitosis/2 mm2 or 10 hpfs, respectively). On the other hand, small cell carcinoma displays densely hyperchromatic smaller tumor cells. Basaloid squamous cell carcinoma shows limited keratinization or intercellular bridges and can show morphologic overlap with large cell neuroendocrine carcinoma Image 7A and Image 7B. Basaloid squamous cell carcinoma also has predilection for the supraglottic location, shows extensive areas of necrosis, and exhibits only focal areas of overt squamous differentiation; however, the immunoprofile is different. Basaloid squamous cell carcinoma is diffusely and strongly positive for high-molecular-weight keratins (CK5/6 and 34βE12) and p63, can show SOX10 positivity, and lacks synaptophysin, chromogranin, and INSM1 reactivity Image 7C and Image 7D.[33,40,44] Conversely, large cell neuroendocrine carcinoma shows variable weak reactivity for p63 and is consistently negative for CK5/6 (high-molecular-weight cytokeratin).[9,40,45]

Image 7.

Basaloid squamous cell carcinoma. A, Infiltrating tumor shows nested, solid, and trabecular growth patterns (x40). B, Highly pleomorphic tumor cells with hyperchromatic nuclei, increased mitotic activity, and apoptotic bodies (x600). p63 (C) and SOX10 (D) immunostains show nuclear staining (x200).

Patients with poorly differentiated neuroendocrine carcinomas often present with advanced clinical stages and have a dismal 5-year overall survival, ranging from 14.4% to 30%.[15,26,40] The majority of patients have disseminated disease at presentation (69.6% with stage IV disease), which typically precludes the option of laryngectomy and neck dissection, leaving chemoradiotherapy as the treatment of choice.[8,15,26,40]

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