Introduction

Xanthogranuloma is an uncommon and chronic inflammatory reaction characterized by the accumulation of foamy macrophages in various body tissues such as the skin, gallbladder, kidney, appendix, breast, bone, female reproductive system, salivary glands, and pituitary gland and is often mistaken for malignancy. [1,2] The most common sites of occurrence are the kidneys and gallbladder. It is rare in the head and neck region, and if they do occur the common sites are orbits, congenital cysts, salivary glands, and intracranial and post-surgical sites. [3,4] No cases have been reported in the thyroid parenchyma. XGI can occur in patients of any age but is mostly found in patients aged 40-60, with a slight female predilection.[5] Herein, we describe a case of XGI of the thyroid in a 76-year-old elderly male who presented with massive neck swelling. To the best of our knowledge, the present case represented the first incidence of thyroid xanthogranuloma without any congenital cysts with no previous history of any surgery.

Case Presentation:

A 76-year-old elderly male presented with anterior neck swelling, which was insidious in onset and progressive in nature. The patient was asymptomatic 30 years ago. There was no history of diabetes and hypertension. There was also no history of smoking and alcohol intake, and he also denied any history of recurrent neck infection or swelling. There was no related family history. On local examination, there was a 25x25 cm huge soft tissue mass involving the thyroid. The swelling extended superiorly to the chin, inferiorly over the sternum and extended to the chest wall. However, the swelling was soft and mobile. The overlying skin was adherent to the mass. (Figure 1)

In laboratory tests, the thyroid function results were normal. The neck ultrasonography showed the thyroid gland, which was replaced by a large, predominantly well-defined lesion which is predominantly anechoic with no increase in vascularity, suggestive of colloid goitre. CECT neck was done, which showed a 25x14x16 cm mass, which was replacing the bilateral thyroid lobes favouring large multinodular goiter with no features of malignant degeneration.

Fine needle aspiration cytology (FNAC) of the lesion was also done, which was non-diagnostic (Category 1). No thyroid follicles or colloids were seen on the smears. Considering the huge multinodular goitre, a total thyroidectomy was planned. Intraoperatively, the giant mass was extending deep to the hyoid bone to preepiglottic space, was adherent to the hyoid bone and was also extending to the base of the tongue, suggesting a thyroglossal cyst.

A total thyroidectomy specimen with removal of hyoid bone was done and sent for histopathological examination. We received a large skin-covered mass measuring 25x17x9 cm. The overlying skin showed multiple sinuses formation. On the cut section, thick, dirty fluid came out. The cyst was unilocular and was filled with necrotic pus-like material. The wall of the cyst was thickened. No normal thyroid parenchyma was identified. (Figure 2) Multiple sections examined show dense and diffuse sheets of histiocytes admixed with plasma cells and lymphocytes. (Figure 3) Large areas of necrosis, fibrosis and chronic degenerative changes like cholesterol clefts and dystrophic calcification were noted. Also seen was normal thyroid parenchyma in the periphery and interspersed between the sheets of histiocytes. (Figure 4)

Figure 1: 25x25 cm huge soft and mobile mass involving the thyroid extending superiorly to the chin, inferiorly over the sternum and extended to the chest wall. Figure 2: Total thyroidectomy specimen with cut section showing a cyst, which was unilocular and was filled with necrotic pus-like material. The wall was thickened. No normal thyroid parenchyma identified grossly. Figure 3: Section showed dense and diffuse sheets of histiocytes admixed with plasma cells and lymphocytes. (Hematoxylin and Eosin stain, 400x) Fig 4: Section showed preserved normal thyroid parenchyma in the periphery and interspersed between the sheets of histiocytes. (Hematoxylin and Eosin stain, 400x)

The important differential diagnosis was Malakoplakia, but no Michaelis Gutmann bodies were observed. Ziehl Neelsen staining was also performed to rule out the possibility of mycobacterium tuberculosis and cystic squamous cell carcinoma. Finally, the diagnosis of XGI the thyroid was rendered. There was no evidence of malignancy or thyroiditis in the background. The post-operatively period was uneventful, and the patient was discharged after one week of surgery and has been in regular follow-up for 12 months and doing well.

Discussion

Xanthogranulomatous inflammation (XGI) is an uncommon inflammatory condition initially described by Oberling as a benign lesion in retroperitoneal organs [5] and was first reported in the genitourinary tract.[6] This is a nonspecific chronic cellular reaction with prominent lipid-laden histiocytes or macrophages, called foam or xanthoma cells, which leads to tissue destruction in the affected organ. Focal xanthogranulomatous changes can be observed in any long-standing lesions or following post-chemotherapy. The formation of mass-like lesions due to extensive XGI is rare, especially in the head and neck region. In some cases, due to the infiltrative nature of the process in adjacent tissues, it is included in the differential diagnosis of malignant tumours both clinically and radiologically.

Based on available case studies to date, XGI rarely affects the head and neck regions; however, when it does, it usually occurs in the orbit, ocular adnexa, and areas with intracranial structural or cystic anomalies (e.g., choroid plexus, Rathke's cleft cyst/craniopharyngioma in the pituitary gland, colloid cyst of the third ventricle), salivary glands, or as a primary neck tumour or following chemoradiotherapy for head and neck cancer. [7] According to Krishna and Dayal, only three cases of XGI in the head and neck region had been published from January 2008 to April 2020, with one case each in the thyroid, thyroglossal cyst, and eye. [8] Chen TP also reported only 11 patients with solitary neck XGI: eight cases involving the parotid gland, two thyroglossal duct cysts, and one second branchial cleft cyst. [3] Additionally, there was one case in the lower jawbone [9] and another in the branchial cleft [4]. Hemmati H et al. identified a mass at the site of a previous subtotal thyroidectomy caused by papillary thyroid carcinoma, which was re-operated on as a recurrence. However, pathology revealed no evidence of recurrence; instead, there was an extensive inflammatory reaction related to xanthogranuloma. [10] Nomura T et al. [11] also documented a case of neck XGI, but the authors were unable to determine the originating tissue. Unlike the previously reported cases, our case is the first instance of neck XGI involving the thyroid without any congenital mass or prior neck procedures.

The etiopathogenesis of XGI is not well understood; however, it can be associated with diabetes and may be caused by infection, post-FNAC trauma, obstruction, foreign body, chemoradiation, or concurrent tumour due to an immune system disorder such as abnormal chemotaxis, lipid transfer issues, or an overreaction to microorganisms like Escherichia coli or Proteus, influenced by genetic predisposition and nutritional status.[8] A pre-existing cyst or glandular tissue is often linked to these uncommon neck occurrences.[3] Typical gross findings include bright yellow or golden yellow mass-like lesions or streaks seen in most organs. Microscopic examination shows variable amounts of fibrous tissue, abscess cavities, micro-abscesses, and a substantial number of lipid-laden macrophages, along with both chronic and acute inflammatory cells. Additional features include foreign body-type and Touton-type giant cells, cholesterol clefts, and hemosiderin deposits.[8] In this case, the bilateral thyroid was extensively effaced by XGI, which transformed into a large cystic cavity filled with necrotic, thick, pus-like material. Due to the limited ability to distinguish neck xanthogranuloma from other diseases solely based on clinical and radiological findings, histopathological examination remains the gold standard for diagnosis. The hallmark microscopic features of XGI include sheets of foamy (lipid-laden) histiocytes, Touton giant cells, and lymphocyte aggregations, with or without necrosis. Differential diagnosis should include other benign histiocytic conditions, such as dendritic cell disorders (further divided into Langerhans cell histiocytosis and non-Langerhans cell histiocytosis) and macrophage disorders (e.g., haemophagocytic lymphohistiocytosis, Rosai–Dorfman disease).[3] Since XGI is entirely benign, it may sometimes regress spontaneously or respond to antibiotics, and it does not recur after complete excision, resulting in a good prognosis.[8] The coexistence of cancer and XGI is rare but documented in the literature.[12] Once a definitive diagnosis is made, extended surgical resection remains the optimal management, with vigilant follow-up essential from the outset of treatment.

Conclusion

Primary xanthogranulomatous thyroid inflammation is rare, especially in a non-diabetic, surgically naive elderly patient. Diagnosing thyroid XGI was difficult in this case because of the absence of specific risk factors, clinical and radiological findings, and inconclusive FNAC. Histopathological examination is essential to exclude other lesions. Due to limited literature on thyroid XGI, its pathophysiology remains unclear. Awareness of this inflammatory condition is important for both pathologists and surgeons to avoid unnecessary extensive surgery and overdiagnosis of malignancy. Careful follow-up is crucial to detect new lesions, early recurrence, or the development of systemic disorders from the initial treatment.

References

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