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Fine Needle Aspiration Cytology

HEAD, NECK AND LYMPH NODES
Stan A. Lightfoot, MD

Fine Needle Aspiration (FNA) of the head and neck can be organized in many ways but preferentially divided into two groups: lumps and bumps and salivary gland lesions.

Lumps and Bumps
History and age are very important. In children the vast majority of these lesions are benign and inflammatory. In adults the majority of lesions are malignant, with the most common cause being metastatic squamous cell carcinoma. History is essential here. Most metastatic squamous cell carcinomas in the neck come from the oropharynx but can uncommonly come from the lung and even less often from a squamous cell carcinoma of the head or face. In the latter case, the diagnosis of the skin cancer has already been made and it is one that has invaded deeply into the dermis or is of longstanding duration.

Lung cancer does not usually metastasize to neck nodes, so that leaves the oropharynx as the site of the primary lesion. Again history is important as at least 80% of these will already have a prior diagnosis of oropharyngeal cancer thus prompting an FNA for staging purposes or assessment of recurrence. At our institution, 20% of the time the patient's primary presentation is metastatic squamous cell carcinoma in a neck lymph node. If the squamous cell in the node is in intimate contact with mature lymphocytes, this is strongly suggestive of a nasopharyngeal primary. Otherwise morphologic features are of little help with regard to location of the primary. When this 20% is worked up, a certain number will have no symptoms or signs that help determine the primary lesion. In these cases blind biopsies of the nasopharynx, tonsil and vocal cords are performed. At our institution, if no tumor is found the patient receives irradiation of the entire head and neck region. This results in a 70% 5 year survival.

Lumps and bumps may also be metastatic malignant melanoma particulary in southern rural populations with high sun exposure. The neck is a favorite site for this lesion and it must be remembered because it can mimic lymphoma, Hodgkin's disease and carcinoma. We will revisit this when we talk about salivary gland lesions below.

If the FNA exhibits an atypical lymphoid proliferation the specimen should be taken for flow cytometry examination. Examination of the case is facilitated by preparing at least one Wright stained slide in addition to several Pap-stained ThinPrep slides in all lymphoid lesions. Several things assist with regard to lymphoid lesions and the FNA. Are the lymphocytes of monotonous or heterogeneous morphology? Are there notches and cuts into the nuclear membrane? Are nucleoli present? The utility of these features is discussed in the attached illustrations.

Lumps and bumps may also be due to benign cysts. In the neck the two most common benign cysts are a branchial cleft cyst or a thyroglossal duct cyst. Both contain many macrophages and a variety of other cells. Cysts may contain atypical squamous cells which may lead to a false positive diagnosis of metastatic disease. If the cyst is tense, and it frequently is, it may feel very firm to the touch. So be wary in the presence of macrophages that you are not dealing with a benign cyst even if there are occasional atypical squamous cells!

I have left the Salivary Gland FNA's for the last discussion, because it is the most difficult topic, requiring experience. FNA's of the salivary gland may be very easy, as in a Warthin tumor or difficult, as in an adenoid cystic carcinoma. However, to be proficient in this area requires abundant experience that cannot be acquired by reading a book. There are several key points regarding the cytology of these glands. The parotid is a favorite site for metastatic disease, notably squamous cell carcinoma. So if the FNA has only well differentiated squamous cell carcinoma, it is almost always metastatic to the parotid. Similar to the neck, lung carcinomas rarely go to the parotid, so a small cell carcinoma in the parotid may indeed be a primary lesion. The lung must be ruled out, but in our experience small cell carcinoma in the parotid is usually primary. And malignant melanoma, true to its name as the great imitator, can complicate the diagnosis of parotid lesions. As an example, recent cases of presumed primary parotid carcinoma and mucoepidermoid carcinoma were in fact metastatic malignant melanomas.

I would like to thank Susan Townsend, CT(ASCP), and Vala Williams, Preparatory Technician, for their help with this project.

References
  1. Al-Khafaji BM, Afify AM: Salivary gland fine needle aspiration using the ThinPrep technique. Acta Cytol 2001; 45:567-74.
  2. Ford L, Rasgon BM, Hilsinger RL, Cruz RM, Axelsson K, Rumore GJ, Schmidtknecht TM, Puligandla B, Sawicki J, Pshea W: Comparison of ThinPrep versus conventional smear cytopreparatory techniques for fine-needle aspiration specimens of head and neck masses. Otolaryngol Head Neck Surg 2002; 126(5):554-61.
  3. Leon ME, Deschler D, Wu SS, Galindo LM: Fine needle aspiration diagnosis of lipoblastoma of the parotid region. Acta Cytol 2002; 46(2): 395-404.
  4. Chen VS M, Qizilbash A , and Young JE : Guides to Clinical Aspiration Biopsy, Head and Neck, 2nd edition. Igaku-shoin Ltd; Tokyo, 1996.

What role does the ThinPrep® technology play in the diagnosis of FNA's from this area? The best way to answer that is to look at the examples:

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