The sinonasal tract is a collective term that refers to the nasal cavity and paranasal sinuses [1].  Despite their anatomical proximity, the diversity in tissue types sand exposures contributes to the wide histological variation.[2] Lesions of the sinonasal tract encompass a wide spectrum of non neoplastic and neoplastic conditions that often pose diagnostic challenges due to overlapping clinical and radiological features; while malignant tumours are relatively uncommon, they typically present late and carry significant morbidity [3,4]The nasal cavity, nasopharynx and paranasal sinuses form functional unit of nose [5]. Sinonasal area is exposed to various infective agents, chemicals, antigens, mechanical and many other influences. These deleterious exposures lead to formation of tumour like and neoplastic conditions [6].

This prospective cross-sectional study was conducted over 18 months (January 2024–June 2025) in department of pathology, Government General hospital, Mahabubnagar. All cases were retrieved and processed via gross examination, routine tissue processing, paraffin embedding, 4–5 µm sectioning, Hematoxylin and Eosin staining following standard protocol. Lesions were classified into Non-Neoplastic and Neoplastic categories with further benign and malignant groups. Tumors were classified according to the World Health Organisation (WHO) histological classification of tumors of the nasal cavity and paranasal sinuses.

In the present study, 80 cases of non-neoplastic and neoplastic lesions of nasal cavity and PNS were studied over a period of 24 months from tertiary care academic institute prospectively. Out of which 60 cases were non-neoplastic and 20 cases were neoplastic. Out of 20 neoplastic cases, 15 cases were benign and 5 cases were malignant.

Table 1 shows the number of patients included in this study along with their histological diagnosis. Among 60 cases of Non-Neoplastic sinonasal lesions.

Rhinosinusitis is most frequently encountered accounting for 32(40%) cases followed by Total Sinonasal polyps accounting for 26(32%) cases. In the polyps, Allergic polyp being the commonest with 10(12.5%) cases followed by equal incidence of Antrachoanal polyp and Inflammatory polyp being 8(10%) cases each respectively. Least being Mucormycosis with 2(2.5%) cases.

 Table 1: Percentage Distribution of Histopathological Findings in Various Sinonasal Lesions

 Figure 1 shows incidence of lesions. Among 20 cases of Neoplastic sinonasal lesions, Benign-neoplastic were accounting for 15(18.75%) cases, in those 5(6.25%) cases were Nasal hemagiomas and with 5(6.25%) cases of Respiratory epithelial adenomatoid hamartoma (REAH), 4(5%) cases of Inverted Papilloma and 1(1.25%) case of Angiofibroma.

Malignant-neoplastic were 5(6.25%) cases with Sinonasal keratinizing squamous cell carcinoma (SCC) 2(2.5%) cases and Sinonasal undifferentiated carcinoma (SNUC) accounting for 2(2.5%) cases and 1(1.25%) case was Olfactory neuroblastoma (ONB).

 Fig.1 incidence of sinonasal lesion according to the present study

 Figure 2 shows distribution of sinonasal lesion shows according to the age. Maximum cases were seen in the 3^rd decade.

 Figure 2: Distribution of sinonasal lesions according to the age

Among the 80 cases of sinonasal lesions analyzed, there was a male predominance, with 43 males (53.75%) and 37 females (46.25%), yielding a M:F ratio of approximately 1.16:1(figure 3).

 Figure 3: Distribution of sinonasal lesions according to Gender

The sinonasal tract, comprising the nasal cavity and paranasal sinuses, is a complex anatomical region exposed to a wide range of environmental influences including allergens, pathogens, chemical irritants, and pollutants. This constant exposure predisposes the tract to a spectrum of inflammatory, infectious, and neoplastic conditions. Clinical presentation often overlaps, with symptoms such as unilateral or bilateral nasal obstruction, epistaxis, facial swelling, anosmia, and blood‑tinged nasal discharge. While radiological imaging and endoscopy aid in localization and assessment of extent, Histopathological examination remains the gold standard for definitive diagnosis and classification of these lesions.

Non‑neoplastic lesions form the majority of sinonasal pathology. Nasal polyps are the most frequent benign lesions, arising from chronic mucosal inflammation and associated with allergy, infection, asthma, and aspirin sensitivity. Histologically, polyps are subdivided into allergic types, characterized by abundant eosinophils, and inflammatory types, which show a paucity of eosinophils. Ethmoidal polyps are generally allergic, whereas antrochoanal polyps are typically inflammatory.

Peak incidence is noted in the second and third decades of life. Despite their benign nature, polyps are clinically significant due to recurrence potential and impact on quality of life. Angiofibroma shows a fibrous stroma with scattered spindle cells and numerous thin-walled, irregular blood vessels lacking muscular support, which explains its tendency for profuse bleeding. Mucormycosis, a broad non-septate hypha causing thrombosis and tissue necrosis with angioinvasion.

Among benign neoplastic lesions, Hemangiomas are prominent vascular tumors of the sinonasal tract. Capillary hemangiomas are frequently encountered. Inverted papilloma with endophytic growth of squamous/transitional epithelium into underlying stroma is also notable; which are multicentric in up to 30% of cases and carry a risk of malignant transformation(figure4). Respiratory Epithelial Adenomatoid Hamartoma (REAH) is an overgrowth of surface epithelium derived medium-sized, ciliated glands surrounded by thickened basement membrane(figure5).

Malignant lesions of the sinonasal tract, though less frequent, present significant diagnostic and therapeutic challenges. Keratinizing squamous cell carcinoma (SCC) is the most common subtype, morphologically identical to squamous carcinomas elsewhere, and characterized by eosinophilic cytoplasm, intercellular bridges, keratin pearls, and irregular nests in desmoplastic stroma. Grading depends on keratinization and atypia, ranging from well‑differentiated tumors with abundant keratinization, prominent bridges, minimal pleomorphism, and low mitotic activity, to poorly differentiated carcinomas with marked atypia, pleomorphism, high mitotic activity, and minimal keratinization. SCCs are frequently associated with local invasion and recurrence, and HPV‑related variants may carry distinct molecular and prognostic implications (Figure 6).

Sinonasal undifferentiated carcinoma (SNUC), defined as an undifferentiated carcinoma lacking glandular or squamous features and considered a diagnosis of exclusion, typically presents as a high‑grade blue cell tumor with necrosis, brisk mitotic and apoptotic activity, and immunoreactivity restricted to pancytokeratin (AE1/AE3) and simple keratins such as CK7, CK8, and CK18 (Figure 7).

Olfactory neuroblastoma (ONB), a rare neuroendocrine tumor arising from the olfactory epithelium, demonstrates a broad histological spectrum that often overlaps with other small round cell tumors. Morphologically, ONB is composed of sharply demarcated nests, lobules, or sheets of small cells with scant cytoplasm in a fibrillary background, often forming pseudo‑rosettes within a richly vascular stroma. Immunohistochemically, ONB is positive for neuroendocrine markers such as synaptophysin and chromogranin, while sustentacular cells highlight with S100 protein (Figure 8).

Management strategies differ according to lesion type. Non‑neoplastic and benign neoplastic lesions generally require surgical excision, while malignant tumors demand multimodal therapy including surgery, radiotherapy, and chemotherapy. Even benign tumors may recur locally, underscoring the importance of complete excision and vigilant follow‑up. Malignant lesions, particularly squamous cell carcinoma, are associated with poor outcomes due to late diagnosis and limited effectiveness of adjuvant modalities. Histopathology, therefore, plays an indispensable role not only in diagnosis but also in guiding prognosis and therapeutic decisions. 

Comparative Overview of Present study with Aman Jain & Prachi Mehta et al. (2025), Rajitha & Srikanth et al. (2021), Kulkarni et al. (2012).

Figure 6: Keratinizing squamous cell carcinoma of the sinonasal tract shows invasive nests of atypical squamous cells with intercellular bridges and keratin pearl formation.

The present study provides a comprehensive overview of the histopathological spectrum of lesions in the nasal cavity and paranasal sinuses. Non neoplastic lesions, particularly chronic rhinosinusitis and inflammatory nasal polyps, were the most prevalent. Among neoplasms, benign tumors outnumbered malignant ones, with inverted papilloma and hemangioma being the most frequent. Because clinical presentations often overlap, histopathological examination remains the cornerstone for definitive diagnosis. Awareness of key histological patterns, including rare entities such as REAH and inverted papilloma, is crucial to avoid misdiagnosis and ensure appropriate management.

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