Low-Grade Epithelial Proliferations of the Sinonasal Tract

Abstract

Low-grade epithelial proliferations of the sinonasal tract include Schneiderian papillomas, respiratory epithelial adenomatoid hamartoma, seromucinous hamartoma and low-grade non-intestinal adenocarcinoma. There is considerable overlap in their clinical presentation, endoscopic appearance, and imaging features. Although well-described diagnostic criteria exist, a definitive diagnosis may be difficult to reach on a small biopsy. Schneiderian papillomas are divided into fungiform, inverted, and oncocytic types, each with characteristic clinical and morphological features. The latter two may progress to malignancy. The majority are still considered to be HPV-related. Two lesions are designated as hamartomas, but their pathogenesis remains uncertain, with inflammatory and neoplastic origins proposed. Respiratory epithelial adenomatoid hamartoma is increasingly being recognized for its association with chronic rhinosinusitis and olfactory cleft site of origin. Seromucinous hamartoma has gained attention in recent years and overlaps with both respiratory epithelial adenomatoid hamartoma and low-grade non-intestinal adenocarcinoma. Controversy surrounds their distinction, particularly from low-grade adenocarcinoma. The latter generally is cured by complete excision, with a 26 % risk of recurrence but rare metastases and deaths from disease.

Keywords: Adenocarcinoma; Nasal cavity; Respiratory epithelial adenomatoid hamartoma; Schneiderian papilloma; Seromucinous hamartoma; Sinonasal tract.

Fig. 1

Fungiform Schneiderian papilloma. a Papillary architecture with a central core arising from the nasal mucosa. b Transitional epithelium without surface keratinization. Note mitotic figure in a suprabasal location

Fig. 2

Inverted papilloma. a Coronal CT scan showing involvement of left nasal cavity maxillary and ethmoid sinuses with hyperostosis of lateral wall of maxillary antrum. b Endoscopic view; note polypoid architecture. c External surface showing cerebriform appearance. d Cut surface showing inverted pale tan ribbons of cells, extending into myxoid vascularized stroma. (CT and endoscopic images courtesy of Dr. E. Massoud, Department of Surgery, Dalhousie University)

Fig. 3

Inverted papilloma. a Closely-packed islands of inverted cells with lobulated architecture. b Squamous epithelium with inflammation. c Islands of cells lined by preserved respiratory epithelium, forming small cysts. d ISP containing largely clear cells

Fig. 4

Variations in inverted papilloma. a Islands of cells with relatively thin respiratory epithelium, resembling REAH. Note lack of distinct periglandular hyalinization. b Hyperplasia of epithelium on the surface of an ISP

Fig. 5

Squamous cell carcinoma arising in an ISP. a Abrupt transition from non-dysplastic ISP (upper and right) to squamous cell carcinoma (lower and left). b Invasive carcinoma with stromal desmoplasia and keratinization

Fig. 6

Oncocytic Schneiderian papilloma. a Exophytic component showing long papillae with eosinophilic cells forming a “fringe”. b Combined exophytic and endophytic components. c, d Proliferating oncocytic epithelium with mucous microcysts and microabcesses

Fig. 7

Respiratory epithelial adenomatoid hamartoma. a Low power image of a septal REAH with broad attachment to stroma. b Ciliated glands with pronounced periglandular hyalinization and intervening chronic inflammation. c Marked goblet cell metaplasia. d A more polypoid REAH (exact site of origin unknown). Smaller seromucinous hamartoma-like glands arise near the tips of the ciliated glands, a feature not compatible with inverted papilloma

Fig. 8

Two seromucinous hamartomas. Both show proliferations of small glands, which bud from elongated, ciliated glands. Note lobular configuration in (a)

Fig. 9

Seromucinous hamartoma. a Proliferation of small, bland glands with minimal intervening stroma. Note budding from ciliated gland in upper right. b Focus of SMH in a nasal polyp. Note the normal seromucinous glands on upper right, with more eosinophilic, granular cytoplasm. P63 was retained around these glands. c p63 showing absence of staining around small glands. d S100 showing positivity of small glands

Fig. 10

Low-grade non-intestinal adenocarcinoma. a Closely-packed glandular proliferation with minimal intervening stroma. b Small fused glandular pattern. c Microcystic pattern. d Solid/nested pattern with occasional slit-like lumens. Note columnar cells with no or minimal atypia. This tumor exhibited no appreciable papillae