Olfactory neuroblastoma

Synonyms:

Esthesioneuroblastoma, neuroendocrine tumor

Definition:

These tumors arise from olfactory epithelium in the upper nasal cavity and above the middle turbinate. It resembles anaplastic carcinoma and may be undiagnosed unless special tumor markers are used.

Cells of origin:

This tumor arises from the stem cells of neural crest origin. These cells are supposed to differentiate into olfactory sensory cells. It should be regarded as one of the primitive neuroectodermal tumors. This tumor is commonly confused with small cell tumors of the nasal cavity.

These tumors appear as exophytic, polypoidal or sessile mass. The mass itself appears smooth and congested. Large tumors may present with surface ulceration. Initially these tumors are unilateral, but ultimately it extends into the opposite side of the nasal cavity and into the adjacent paranasal sinuses with continued growth.

Features of olfactory neuroblastoma:

1. Very few cases have been reported (rare)

2. Presents usually with nasal obstruction and mass

3. Almost all age groups are affected

4. Urinary VMA and Homovanillic acid cannot be usually detected

5. Shows bimodal age distribution with two peaks (around 20 and 50 years)

6. The term Neuroendocrine tumors is proposed to describe this tumor in older age group

7. Young patients show less local recurrence and more metastasis

8. Old patients show more common local recurrence and less metastasis

These tumors are very slow growing tumors.

Clinical staging:

Group A tumors: Are confined to the nasal cavity

Group B tumors: Involves the nasal cavity and one or more of paranasal sinuses

Group C tumors: Extends beyond these limits and erodes the cribriform plate

Classification of olfactory neuroblastoma:

1. Neuroblastoma proper: This group can be subdivided into those manifesting olfactory differentiation and those without such histological evidence.

2. Neuroendocrine carcinomas

Neuroblastomas proper:

Neuroblastomas without olfactory differentiation are composed of sheets of poorly demarcated groups of cells separated by fine connective tissue trabeculae. These cells are small and mitosis are rather unusual in them. The most important criteria is the presence of fibrillary material between the tumor cells. Foci of necrosis with small calcified deposits are also found. Holmer-Wright rosettes can also be seen.

These rosettes are nothing but a ring of neuroblastoma cells encircling a small space filled with neurofibrillary material.

Olfactory rosettes are the hallmark of neuroblastomas with olfactory differentiation. These rosettes are acinar spaces ringed by tall columnar cells with pseudostratified nuclei and contains small amounts of mucin and cellular debris.

Neuroendocrine carcinomas: These tumors manifest a unique feature of being admixed with glands. In some instances, the neoplastic cells are intimately related to the basal epithelium of the glands. Neurofibrillary component is not seen and the growth pattern is solid nests without rosettes.