From the Guidelines
Anucleated squames and keratinous debris in FNA smears are non-specific findings that may represent benign or malignant conditions, and therefore, require correlation with clinical information, imaging findings, and sometimes additional sampling or histological confirmation to establish a definitive diagnosis. These findings are characterized by flattened, plate-like cells that have lost their nuclei during the normal maturation process of squamous epithelium, along with fragments of keratin material 1. When observed in FNA samples, these elements may represent normal skin contamination during the needle passage, sampling of a benign squamous lesion like an epidermal inclusion cyst, or potentially a squamous cell carcinoma.
The distinction between benign and malignant causes depends on additional cytologic features such as nuclear atypia, abnormal keratinization patterns, and cellular arrangement 1. In skin or superficial lesions, these findings are often expected, but when found in deep organ aspirates, they may raise concern for malignancy, particularly if accompanied by nuclear abnormalities. According to the clinical practice guideline for the evaluation of the neck mass in adults 1, an adequate and negative FNA should not preclude additional diagnostic procedures for a patient with worrisome signs and symptoms.
Some key points to consider in the interpretation of FNA results include:
- The importance of distinguishing between an inadequate specimen and an adequate but indeterminate specimen 1
- The potential benefits of repeat FNA in cases with inadequate results or a diagnosis of benign pathology 1
- The use of ultrasound-guided FNA to increase specimen adequacy and diagnostic yield 1
- The value of on-site evaluation by a cytopathologist in reducing the inadequacy rate of FNA 1.
In terms of diagnostic approaches, fine-needle aspiration (FNA) is considered the best initial test to diagnose a neck mass 1, but core biopsy or open biopsy may be necessary in some cases to establish a definitive diagnosis. Ultimately, a comprehensive diagnostic approach that incorporates clinical information, imaging findings, and cytologic features is necessary to determine the significance of anucleated squames and keratinous debris in FNA smears 1.
From the Research
Anucleated Squames and Keratinous Debris in FNA Smears
- Anucleated squames and keratinous debris in FNA smears can be associated with various conditions, including subareolar abscess of the breast 2, squamous-lined cysts of the pancreas 3, and keratinized squamous cells in fine needle aspiration of the brain 4.
- In the context of subareolar abscess of the breast, anucleated squames and keratinous debris are often seen in combination with neutrophils, cholesterol crystals, and parakeratosis 2.
- In squamous-lined cysts of the pancreas, anucleated squames and keratinous debris can be found along with macrophages, lymphocytes, and benign squamous fragments 3.
- The presence of anucleated squames and keratinous debris in FNA smears of the brain can be indicative of craniopharyngioma, metastatic squamous cell carcinoma, epidermoid cyst, or Rathke cleft cyst 4.
- In cervical/vaginal smears, extensive hyperkeratosis characterized by patches of anucleated squames can be a significant marker of underlying neoplastic disease 5.
- In fine needle aspiration cytology of the breast, the presence of squamous cells, including anucleated squames, can be associated with both benign and malignant lesions, such as metaplastic carcinoma, fibroepithelial tumors, and subareolar abscess 6.