Marginal vacuoles in fine needle aspiration biopsy smears of toxic goiters

Functional State of Cells During their Life and on their Journey Toward Inactivity and Death: Search for Morphological Evidence in Thyroid Fine Needle Aspiration Smears

Synthesis and storage of thyroglobulin as well as synthesis of thyroid hormones and their release into the circulation are important functions of thyroid, which were studied in fine needle aspiration (FNA) smears from thyroid lesions. Evidence of thyroglobulin synthesis was demonstrated in neoplastic and nonneoplastic follicular cells, especially in Hürthle cells, in the form of colloid inclusions. Whereas the pinocytic vesicles containing colloid at the luminal end of in nonneoplastic and neoplastic follicular cells indicated engulfment of colloid for synthesis of thyroid hormones (T₃ and T₄), the marginal vacuoles (MVs) (fire-flare appearance) at the basal aspects of follicular cells suggested their release on way to the interfollicular capillaries. The morphological evidence of secretary activity could also be demonstrated in medullary thyroid carcinoma (MTC) in the form of azurophilic granules, marginal vacuoles, and intracytoplasmic lumina (ICL) with secretions; the secretory material, likely to be amyloid, present in MTC cells, and their release to the extracellular space was confirmed by positive immunocytochemical staining for calcitonin. It was found that nuclear grooves and related intranuclear cytoplasmic inclusions (INCIs) in papillary thyroid carcinoma (PTC) possibly represent an initial step of a degenerative process leading to formation of inactive cerebriform nuclei. Based on observation regarding formation and release of precursor substances for psammoma bodies (PBs), it was also suggested that PBs may not represent a process of dystrophic calcification over infarcted/dead papillae but suggest an active biological process, which leads to inhibition of growth of neoplastic cells and acts as a barrier against spread of PTC.

The Diagnostic Role of the Marginal Vacuoles in FNAC of Solitary Thyroid Nodules

CONTEXT

FNAC thyroid is more sensitive as well as specific in segregating neoplastic and non-neoplastic thyroid lesions. Identification of predominant cell pattern, cell morphology and background details in FNAC smears play an important role in categorisation of various thyroid lesions with accuracy. Marginal vacuoles (MVs) have been described as irregular cytoplasmic vacuoles with largely unstained central area. MVs, although suggestive of thyrotoxicosis, are non-specific, as they are also encountered in non- toxic goitre, Hashimoto's thyroiditis and follicular carcinoma. This cytologic finding therefore deserves further study to precisely delineate its utility. Aims & Objective: To investigate whether MVs have a diagnostic role in FNAC of solitary thyroid nodule Setting & Design: This study was conducted on 40 patients who presented with solitary thyroid nodule.

METHODS & MATERIAL

Forty patients having solitary thyroid nodule were subjected to FNAC on an outpatient basis. Their cytomorphological features were studied with special attention to presence of MVs. MVs if present were then graded as no/ scant (gradeI ), moderate (gradeII) and abundant (gradeIII).

RESULTS AND CONCLUSION

Majority (77.5%) of nodular goitres had insignificant MVs (gradeI) in their smears. Significant MVs (gradeII+III) were limited to autoimmune thyroiditis presenting as solitary nodule and follicular neoplasms. Abundant MVs/ gradeIII were seen in follicular neoplasm only. MVs were not present in rest of neoplastic goitres. This implies that MVs are a marker of follicular differentiation.